Building OpenSocial Apps- P3

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Building OpenSocial Apps- P3

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Building OpenSocial Apps- P3: Nhà phát triển của Thư viện Series từ Addison-Wesley cung cấp hành nghề lập trình với độc đáo, tài liệu tham khảo chất lượng cao hướng dẫn về các ngôn ngữ lập trình công nghệ mới nhất và họ sử dụng trong công việc hàng ngày của họ. Tất cả các sách trong thư viện của Nhà phát triển được viết bởi chuyên gia công nghệ các học viên những người có kỹ năng đặc biệt tại các tổ chức và trình bày thông tin một cách đó là hữu ích cho các lập trình viên khác....

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  1. 74 Chapter 5 Communication and Viral Features // Update the UI for the failures for(var i = 0; i < failure.length; i++){ clicked = current_list.list_dom["myspace.com:" + failure[i]]; if(clicked) clicked.style.backgroundColor = "red"; } } } } So, there is a lot going on here.The callback for requestShareApp is especially important.The first thing that really happens is that the various types of errors are trapped, and an error message is displayed if one is found. If there was no error, we cycle through the list of currently selected users, revert the background of the corresponding div tags to white, and reset the list.There are now two possibilities: the user either canceled the pop-up or hit Send. If the pop-up was canceled, there’s no more work to do. If the pop-up wasn’t canceled, the user must have hit the Send button, so we need to figure out who the actual recipients were.We do this by accessing the responseValues object in the ResponseItem that’s passed back to us. responseValues contains two arrays: One, success, contains the list of users who were successfully sent an invite.The other, failure, contains the list of users who had an error occur when the invite was sent. Both arrays contain the integer IDs of the specified users. There are a couple of things to note when accessing the success and failure arrays. First, users who already have the app installed won’t get the invite, but neither will they show up in either array. Second, the IDs in the array are integers, so they don’t exactly match the IDs that are sent by the API (in the format "myspace.com:6221"). Back to the function at hand.We extract the success and failure arrays and loop through them.We turn the background color of all the successful recipients to green, and that of all the failures to red.You’ll notice that we have to append "myspace.com:" to the beginning of each ID so it matches up with the IDs we fetched from the API. It may be useful to add a More button to your app, something like “Select Random 20” that will randomly select 20 of the user’s friends.This will help encourage users to share the app with a larger group of friends; turning 20 clicks into one click makes it much easier for your users. Using opensocial.requestSendMessage to Send Messages and Communications Let’s examine how opensocial.requestSendMessage works.The requestSendMessage function provides a number of ways for apps to communicate with users. MySpace supports the following message types: n Send Message: a private one-to-one message that will arrive in the user’s Mail Center in-box n Comment: a public one-to-one message that will appear on the user’s Profile page in the Comments section Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  2. Using opensocial.requestSendMessage to Send Messages and Communications 75 n Bulletin: a one-to-many message that will appear in the Bulletins module of each of the user’s friends’ Home pages n Blog: a one-to-many message that will appear on a MySpace user’s Blog n Profile: not a message per se; allows an app to edit/update the user’s Profile.The following Profile sections can be edited and are chosen by the user in a drop- down menu: About Me I’d Like to Meet Interests Edit Artist Profile Movies Television Books Heroes Defining requestSendMessage opensocial.requestSendMessage has the following signature: opensocial.requestSendMessage = function(recipients, message, opt_callback, opt_params) You probably noticed that the signature for opensocial.requestSendMessage is very similar to that of opensocial.requestShareApp.The big difference is that you’re allowed to define only one recipient ID at a time; the container will reject an array of IDs. Similar to requestShareApp, however, are opt_callback, which is the function that’s invoked when the pop-up modal has closed, and opt_params, which is unused. Note Some targets don’t require a recipient; these are Bulletin, Profile, and Blog. Any recipient value passed in for these targets will be ignored. The message parameter is an object of type opensocial.Message.The supported content of the message depends on the message type; here’s a quick breakdown: n Types that support a message title are Send Message, Comment, Bulletin, and Blog. The title doesn’t support any HTML markup. n All of the message types support a message body. All support some HTML markup in the body.Tags like , , and are stripped out, but tags like , , , and are allowed. When creating the opensocial.Message object, you need to specify the opensocial.Message.Field.Type property; this specifies which of the message types Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  3. 76 Chapter 5 Communication and Viral Features Table 5.1 Supported Message Types Message Type Value of opensocial.Message.Field.Type Send Message opensocial.Message.Type.PRIVATE_MESSAGE Comment opensocial.Message.Type.PUBLIC_MESSAGE Bulletin opensocial.Message.Type.NOTIFICATION Blog MyOpenSpace.PostTo.Targets.BLOG Profile MyOpenSpace.PostTo.Targets.PROFILE will be sent.Table 5.1 shows the list of supported types and the opensocial.Message. Field.Type fields to which they correspond. Profile and Blog are MySpace-specific extensions and not in the OpenSocial spec, which is why they’re namespaced a little differently. In the code that follows, we’ll show you how to make use of the message types when using requestSendMessage. Writing the requestSendMessage Code Now that we’ve defined our requestSendMessage function, let’s plug it into our Tic-Tac- Toe app and try it out.The following example function wraps requestSendMessage and is useful if you want to use requestSendMessage in multiple places throughout your app: function rsmWrapper(id, subject, body, type, callback){ var param = {}; param[opensocial.Message.Field.TYPE] = type; param[opensocial.Message.Field.TITLE] = subject; var message = opensocial.newMessage(body, param); opensocial.requestSendMessage(id, message, callback); } Note that the function is fairly similar to the requestShareApp wrapper.This function just requires two additional parameters to construct the opensocial.Message object: subject and type.The type parameter corresponds to one of the opensocial.Message.Field.Type values found in Table 5.1. Now that we have our requestSendMessage wrapper, we can make use of it in the app by creating different types of messages. A fairly simple and effective type of message is a bulletin; it is a one-to-many message that gets blasted out to all the user’s friends. function rsmBulletin(){ var this_app = opensocial.getEnvironment().currentApplication; var profile_link = this_app.getField(MyOpenSpace.Application.Field.PROFILE_URL); var image_link = this_app.getField(MyOpenSpace.Application.Field.ICON_LARGE); Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  4. Using opensocial.requestSendMessage to Send Messages and Communications 77 var subject = "Social Tic-Tac-Toe is Here!"; var body = "Hey everyone! I' m playing TTT online with my friends, come"; body += "play a game with me!"; body += ""; rsmWrapper(opensocial.IdSpec.PersonId.VIEWER, subject, body, opensocial.Message.Type.NOTIFICATION, rsmBulletinCallback); } Since bulletins don’t use any template messaging, we have to generate all the links ourselves.To do this, we make use of the instance of a MyOpenSpace.Application object for this app.When an app is rendered, the MySpace platform pushes down a script-accessible representation of the app’s information.This object may be accessed from the environment with the call opensocial.getEnvironment().currentApplication Specific data that may be found in this object includes: 1. App ID, accessed via the field enum MyOpenSpace.Application.Field.ID 2. Name, accessed via the field enum MyOpenSpace.Application.Field.Name 3. Profile URL, accessed via the field enum MyOpenSpace.Application.Field. PROFILE_URL 4. Install URL, which for right now is the same as the Profile URL (which is where the app is installed from), accessed via the field enum MyOpenSpace. Application.Field.INSTALL_URL 5. Canvas URL, accessed via the field enum MyOpenSpace.Application. Field.CANVAS_URL 6. The 64 64 icon URL, accessed via the field enum MyOpenSpace.Application. Field.ICON_LARGE 7. The 16 16 icon URL, accessed via the field enum MyOpenSpace.Application. Field.ICON_SMALL The Application object behaves just like the Person object—data is accessed through the getField function. For example, to access the app’s name in your script code, you would make the following call: opensocial.getEnvironment().currentApplication.getField( MyOpenSpace.Application.Field.NAME); Here we use the app’s Profile URL and the large icon to generate the bulletin mes- sage. Some of the supported HTML tags are also used for the body.Then the wrapper function is called and voilà! We’ve sent our first message! Bulletins are great for getting the word out to a large audience, but they lack a per- sonal touch. In our Tic-Tac-Toe app, one user can challenge another user to a game. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  5. 78 Chapter 5 Communication and Viral Features When this challenge is initiated, we send out a message from the challenger to the challenged.The code for that looks like this: function rsmMessage(){ var current_list = TTT.Lists.getCurrentList(); var id = this.list_index; TTT.Lists.itemClicked = id; var this_app = opensocial.getEnvironment().currentApplication; var profile_link = this_app.getField(MyOpenSpace.Application.Field.PROFILE_URL); var image_link = this_app.getField(MyOpenSpace.Application.Field.ICON_LARGE); var subject = "I challenge you to a TTT duel!"; var name = ""; for(var i = 0; i < current_list.list.length; i++){ if(current_list.list[i].getId() == id){ name = current_list.list[i].getDisplayName(); break; } } // If the name isn't empty, add a space before the name name = ("" === name) ? name : " " + name; var body = "Hey" + name + "! You've been challenged to "; body += "a game of Tic-Tac-Toe, click "; body += "here to accept the challenge!"; body += ""; rsmWrapper(id, subject, body, opensocial.Message.Type.PRIVATE_MESSAGE, rsmMessageCallback); } This code is fairly similar to the bulletins code.We use the MyOpenSpace. Application object to generate a message and then invoke the wrapper.There is also some app-specific code in this function that determines the ID and name of the challenged user; this ID is sent into the wrapper while the name is used to personalize the message. Adding a person’s name to a message is an old trick that helps the message seem a little less like a form letter. Callback in requestSendMessage The callback for requestSendMessage works the same as requestShareApp. An error could be generated before the modal dialog is shown; otherwise the value 1, 0, or 1 is returned. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  6. Getting Your App Listed on the Friend Updates 79 Let’s take a look at one quick example: function rsmMessageCallback(response){ var div = TTT.Tabs.getCurrentContainer().firstChild; if(response && !response.hadError()){ if(0 === response.getData()){ div.innerHTML += "challenge cancelled..."; } else if(1 === response.getData()){ div.innerHTML = "challenge sent!"; } } else{ log("Oops, there was an error, try refreshing the page!"); } } First we check for an error. If one was found, we display an error message asking the user to refresh the page. Most errors that occur with the messaging system are intermittent and can be fixed with a refresh. If there was no error, a simple message is displayed reaffirming the user’s action. Getting Your App Listed on the Friend Updates with opensocial.requestCreateActivity Basics On every user’s MySpace Home page there is a module that displays the user’s Friend Updates.These updates are a feed and might include information like “John added a new photo,”“Mary and John are now friends,” or “Susan installed the Tic-Tac-Toe application.”These updates are ordered by date, and the newest information is always displayed on top. When an app creates an activity, the activity appears in this feed.That makes any app activity a one-to-many message that will appear in the Friend Updates feed for each of the user’s friends.With activities, applications can define numerous custom messages that will appear in a user’s Friend Updates. Activities can be created only from the app’s Canvas surface, but they’re a great way to embed your app into a user’s MySpace experience and promote your application at the same time. Defining opensocial.requestCreateActivity opensocial.requestCreateActivity has the following signature: opensocial.requestCreateActivity = function(activity, priority, opt_callback) This means it’s a function that must include an activity (opensocial.Activity), a priority (opensocial.CreateActivityPriority) setting for the request, and opt_callback as the function to call once the request has been processed. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  7. 80 Chapter 5 Communication and Viral Features Note At the time of this writing, opensocial.CreateActivityPriority is not being checked or used by MySpace. You’ll notice in the code that follows that we always pass in a value of high (opensocial.CreateActivityPriority.HIGH) as opposed to low (opensocial.CreateActivityPriority.LOW). If you have opensocial.CreateActivityPriority in your code and MySpace starts making use of it, the behavior of your app may be affected, so it’s good to keep this in mind should your app suddenly start doing something. Let’s take a quick look at how OpenSocial defines the priorities: High: If the activity is of high importance, it is created even if this requires asking the user for permission.This might cause the container to open a user flow that navi- gates away from your gadget. Low: If the activity is of low importance, it is not created if the user has not given permission for the current app to create activities.With this priority, the requestCreateActivity call never opens a user flow. Using the Template System to Create Activities One of the most important elements of creating and raising activities is the template system. In fact, it’s so important that it needs to be explained before we start looking at code. Unlike messages, which are completely defined and passed into the function as static text, activities make use of a custom template system. Basically, you create a template for your activities’ messages and the variables are resolved at runtime.Templates must be used for activities. Every template must have a title containing up to a maximum of 160 visible characters. Each template may also optionally specify a body having up to 260 visible characters. Your message template is based on a text string with some optional variables (which you may occasionally hear referred to as “tokens”) thrown in.These variables are replaced by real data once the activity is raised. A basic activity’s message might look something like this: "Susan installed Tic-Tac-Toe on: ${date}." When the template is run, you’ll specify that ${date} will be replaced with a string containing the current date and time. So, if you give the variable ${date} a value like “September 28, 2010,” the resulting message would read “Susan installed Tic-Tac-Toe on: September 28, 2010.” Data Types In our first example, the ${date} variable was a string. However, you can also specify the data type of a variable.The two currently available data types are Literal and Person. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  8. Getting Your App Listed on the Friend Updates 81 A Literal data type, used in our first date example, is any string.Your variable is then simply replaced by that straightforward string. A Person data type is slightly more complex. If a variable is defined as a Person data type, the variable is then replaced by a person’s display name and a link to the person’s Profile when it appears in the feed. For example, let’s say we have a template where the variable ${opponent} is of type Person. It might look like this: "You've been bested at Tic-Tac-Toe by ${opponent}." To get this template message to display correctly, you need to pass in the opponent’s user ID. For example, if we pass in the string "6221" (Tom’s ID) for our ${opponent} variable, our message would read “You’ve been bested at Tic-Tac-Toe by Tom.” The word Tom would then link to Tom’s Profile. Reserved Variable Names There are a number of variables that are reserved (see Table 5.2), but the most interesting one is ${sender}. This is because ${sender} is actually a required variable in your template title, meaning you’ll be using it a lot. The variable ${sender} is a Person-type variable, which means it’s replaced by the Viewer’s name and Profile link. For example, let’s say we changed our template to read "${sender} raised this event, making ${sender} the Viewer!" If Susan were to raise an event with that variable, the resulting message would read “Susan raised this event, making Susan the Viewer!” Table 5.2 Reserved Variable Names Reserved Variable Name Use ${subject} Replaced with a link to the Viewer’s Profile and the Viewer’s display name as the corresponding text ${subject.DisplayName} Replaced by the Viewer’s display name (no link) ${subject.Id} Replaced by the Viewer’s ID ${subject.ProfileUrl} Replaced by the Viewer’s Profile URL ${canvasUrl} Replaced by the app’s Canvas URL ${variable_name.Count} Used when variables are aggregated and where variable_name is the name of a variable used in the template Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  9. 82 Chapter 5 Communication and Viral Features But if her arch-nemesis,Tom, raised the event, the message would read “Tom raised this event, making Tom the Viewer!” In each instance the Viewer’s information is used for the ${sender} variable. Aggregation When a user has a large number of applications, and friends who like applications, the user’s feeds can get crowded with information and updates. Because of this, activity feeds are aggregated. If a user has five friends all playing Tic-Tac-Toe and raising activities for the app, all of those activities are aggregated into a single feed entry for Tic-Tac-Toe. For example, let’s create a new message template and see what would happen when it’s raised multiple times. Let’s start with a new template: "${sender} is playing Tic-Tac-Toe with ${opponent}." In this example we’d want to aggregate the ${opponent} variable (you can learn how to specify aggregated variables by skipping ahead to the section on using the Template Editor). The first time I raise the event, my opponent’s ID is "6221" (Tom, again!).The resulting message reads “Susan is playing Tic-Tac-Toe with Tom.” If Susan raises the event again, this time challenging her friend Matt to a game, the resulting message reads “Susan is playing Tic-Tac-Toe with Tom and Matt.” And if Susan raises the event a third time, but this time challenging Tila Tequila to a battle of Tic-Tac-Toe, the resulting message would read “Susan is playing Tic-Tac-Toe with Tom, Matt, and Tila!” Now that’s a game I would like to see. Notice that not only does the templating sys- tem keep aggregating your message feeds, it also makes them grammatically correct by adding commas and the word and. Body and Media Items We have variables and data types, but there’s more to a message template than that. What about pictures and the message itself? That’s where body and media items come into play. The body is similar to a template’s title, but it’s optional and can hold more charac- ters. If you include a body, it displays on the second line under your specified title. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  10. Getting Your App Listed on the Friend Updates 83 Media items can be any picture on MySpace that’s accessible to the Viewer. In Chapter 3, Getting Additional MySpace Data, we fetched a list of the Viewer’s photos, displayed them on the page, and allowed the player to select one for a custom board back- ground. If a custom background is selected, it is used as a media item in any raised activity. You’re allowed to include a maximum of three media items in a message template. All will be rendered on the second line of the message. Using the Template Editor to Create Templates Now that you know how templates work, you’re ready to create some new templates for your app.To do this, you’ll use the Template Editor tool found on your My Apps page. Under each application there is a tool entitled Templates (Figure 5.6); click it to be taken to your Templates page (shown in Figure 5.7). Click on Create Template to create new templates for your app.This will take you to the template creation screen. From this screen (Figure 5.8) you can edit existing templates or create a new one. Let’s look at an existing template for our Tic-Tac-Toe application. Figure 5.6 Screen shot of My Apps S Templates link Figure 5.7 Screen shot of an existing Templates list Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  11. 84 Chapter 5 Communication and Viral Features Figure 5.8 Screen shot of the Templates screen On the individual Template screen, you can see all of the pertinent template informa- tion. Under Content you’ll find the template’s name and unique identifier along with the title and the body.There are also separate tabs for Single Form instances (when just one activity is raised) and Aggregate Form instances (multiple activities are raised). Under Variables, you can add and specify data types and even test values for each of your variables. Below this section are sample media items that you can use to test how they’ll appear when you preview or run your template. To test your template, click the Preview Template button.This creates a preview of your template in the bottom portion of the screen using the test data you indicated under Variables and Media Items. You’ll also be provided with sample JavaScript code that can be used to raise the event.You can actually just cut and paste this code into your app to begin raising activi- ties, but you’ll most likely want to customize it (see “Raising the Event” in the follow- ing section). If you’re satisfied with your template, click the Save Template button to save your template for later use. Once your template is saved, you can switch it from development status to live status. To do this: 1. Go back to your Templates page. 2. Click the Publish button next to the template you want to make live. 3. Click OK when prompted. From your Templates page you can also delete or edit an existing template. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  12. Getting Your App Listed on the Friend Updates 85 Using opensocial.requestCreateActivity Now that we understand what opensocial.requestCreateActivity looks like and how to construct a template, let’s actually use the function. Raising the Event The template we’re using for our activity is the following: ${subject} has started a game of Tic-Tac-Toe against ${opponent} We’re doing something a bit tricky with the href attribute in the anchor tag.This actually allows us to send custom parameters into the Canvas surface of the app if the link is clicked.This can be especially useful for tracking purposes.You can try different mes- sages, each with a different ${params} value, and see which one is clicked more often. The actual code to raise the event looks like the following: function raiseActivity(){ // Create the parameters var param = {}; // Required template name param[opensocial.Activity.Field.TITLE_ID] = "x_and_y_started_game"; // The actual parameter values param[opensocial.Activity.Field.TEMPLATE_PARAMS] = { "opponent" : currentGame.opponentId, "params" : "{\"from\":\"act\"}" }; // Check if a custom background is set to use for // a media item if(currentGame.customBG.usingCustomBG()){ // Get the photo object var photo = currentGame.customBG.photo; // Parse out the URI var uri = photo.getField(MyOpenSpace.Photo.Field.PHOTO_URI); // Create the opensocial.MediaItem object var media_item = opensocial.newMediaItem("image/jpeg", uri) // Stick it in an array var media_item_array = [ media_item ]; // Insert the array into the parameters param[opensocial.Activity.Field.MEDIA_ITEMS] = media_item_array; } Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  13. 86 Chapter 5 Communication and Viral Features // Create the opensocial.Activity object var activity = opensocial.newActivity(param); // Raise the activity! opensocial.requestCreateActivity(activity, opensocial.CreateActivityPriority.HIGH, raiseActivityCallback); } First, the activity template is defined as "x_and_y_started_game".This is the unique identifier for the desired template and can be found in the Template Editor under Template Name. The template variables are then given actual values; the ${opponent} variable is assigned the value of the ID of the opponent, and the ${params} variable is assigned a JSON object.This is an example of how you might use different template messages for tracking purposes, since here we’re saying the user got to the Canvas page from an activ- ity. Meanwhile, the two variables correspond to the list of variables in the Template Editor under Variables. The next block of code attaches a media item to the activity. A couple of things to note here: First, the media item URI must conform to an API-style URI and not a reg- ular old URL, such as www.example.com/my_picture.jpg.The best way to get these API URIs is through the API itself, as we do here in the app. In our code we fetch the list of photos for a user and save those values into a list. When a photo is selected, we match it to the correct entry in the list and parse out the URI.This URI is accessed from the MyOpenSpace.Photo object using the MyOpenSpace.Photo.Field.PHOTO_URI. The second thing to note is that an activity requires an array of media items. So, even if you have only one media item, make sure to stick it in an array. Once all the parameters are set up, the opensocial.Activity object is created and it’s passed into requestCreateActivity. Note What are we doing there with the custom parameters in the template? Well, custom values can be passed into an app’s Canvas surface by appending an "appParams" key to the query string. So, for example, by appending &appParams={"hello"%3A"goodbye"%2C"from"%3A"act"} to the end of the Canvas URL, we pass the JSON object { "hello" : "goodbye", "from" : "act" } into the app. These values can be picked up inside the Canvas by doing the following: gadgets.views.getParams().hello; gadgets.views.getParams().from; In this case, the first line resolves to "goodbye" and the second to "act". Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  14. Getting Your App Listed on the Friend Updates 87 Using Activity Callbacks to Combat Permission-Denied Errors Uh-oh! Permission denied? It turns out that a separate permission is required to raise an activity for a user. If this permission isn’t set, the container blocks the request and returns an error. So that’s that, I guess. Oh well, better luck next time… Not necessarily; opensocial.requestPermission to the rescue again! In a method similar to one used in Chapter 3, Getting Additional MySpace Data, where we requested permission to fetch photos, we can request permission here to raise an activity: function raiseActivityCallback(response) { // Check for an error if(response.hadError()){ // Was the error a permission issue? if(response.getErrorCode() === opensocial.ResponseItem.Error.UNAUTHORIZED){ // Beg for permission var reason = "To inform your friends of your upcoming match!"; // Pick which permission // STICK IT IN AN ARRAY!! var perm = [MyOpenSpace.Permission.VIEWER_SEND_UPDATES_TO_FRIENDS]; // Pretty please ... opensocial.requestPermission(perm, reason, actPermCallback); } else{ // Some other error log("Oops, there was an error, try refreshing!"); } } } If there was an error, we first check whether it was a permissions error. If so, we spec- ify why we want the permission and which permission we want. Again, don’t forget to stick the MyOpenSpace.Permission object into an array or it will be rejected. Once requestPermission is closed, it will invoke the specified callback function. Let’s take a look at it: function actPermCallback(response){ // Was permission granted? if(!response.hadError()){ // Yay! raiseActivity(); } } Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  15. 88 Chapter 5 Communication and Viral Features Very simple; if no new permissions were granted, the response has an error. No error means the permission has been granted, so retry the activity.This is a great way to ensure that the activity is sent while also providing a nice flow for the user. Sending Notifications The fourth and final way to communicate with your users is the app notification. Notifications are great for turn-based games as they are a quick and easy way to let players know when it’s their turn in the game.This is exactly how we use them in our Tic-Tac-Toe app. It’s also highly regarded because it’s the only message type that doesn’t require the user’s confirmation. When using notifications, you have to watch that you’re not spamming your users.You could be shut down, or worse, you’ll annoy your user base and lose installs. But, if you keep it reasonable, notifications are a great way to increase user engagement. When a user gets a notification, he or she gets an indicator on the Home page saying a new notification has arrived. Clicking on the indicator takes the user to the Mail Center, where he or she will see the message in the notification folder. Each notification can have zero to two buttons to allow the user to take some action. In our Tic-Tac-Toe app, we tell users it’s their turn and provide one button to take them back to the Canvas page to play the game. Notifications are a MySpace-specific extension, but they are patterned after requestCreateActivity, so the code should be somewhat familiar. Let’s take a look at what that means: // Wrap requestCreateNotification function rsmNotification(recipient, game_id){ // Create the body text var body = "Hi ${recipient}, it's now your turn"; body += "in Tic-Tac-Toe!"; // Create the button that links to the Canvas var url1 = MyOpenSpace.NotificationButton.UrlTypes.CANVAS; var params1 = { "game_id" : game_id, "recipient" : recipient }; var text1 = "Take Your Turn!"; var button1 = MyOpenSpace.newNotificationButton(url1, text1, params1); // Create the button that links to the app's Profile var url2 = MyOpenSpace.NotificationButton.UrlTypes.APP_PROFILE; var text2 = "Check out Tic-Tac-Toe"; var button2 = MyOpenSpace.newNotificationButton(url2, text2); var param = {}; Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  16. Sending Notifications 89 param[MyOpenSpace.Notification.Field.BODY] = body; param[MyOpenSpace.Notification.Field.BUTTONS] = [button1, button2]; var mediaItemArray = []; mediaItemArray.push(opensocial.newMediaItem( "", MyOpenSpace.MediaItemHelper.PROFILE_PICTURE)); param[MyOpenSpace.Notification.Field.MEDIA_ITEMS] = mediaItemArray; var notification = MyOpenSpace.newNotification(param); MyOpenSpace.requestCreateNotification( recipient, notification, rsmNotificationCallback); } Notifications use a built-in template, similar to requestShareApp. However, only the variables ${recipient} and ${canvasUrl} are available, and you’ll need to use the activities-style variable format ${variable_name}, as opposed to the requestShareApp style of [variable_name]. The button is defined by a MyOpenSpace.NotificationButton object.This object has three fields: n MyOpenSpace.NotificationButton.URL n MyOpenSpace.NotificationButton.PARAMS n MyOpenSpace.NotificationButton.TEXT The URL can be one of two values: MyOpenSpace.NotificationButton. UrlTypes.CANVAS or MyOpenSpace.NotificationButton.UrlTypes. APP_PROFILE. You probably won’t want to take your users back to your app Profile, especially con- sidering that only users who have installed the app receive notifications. Here, we want to take the user back to the Canvas instead. The PARAMS field allows us to define custom parameters that are sent into the Canvas page. In our Tic-Tac-Toe app, we append three custom parameters—essentially creating a tracking parameter.This parameter is used to let us know that a user came to the Canvas from a notification, what action the user wants to take, and which game the user wants to play. Once the button is created, we’re ready to create the MyOpenSpace.Notification object itself.We assign the body text first, using MyOpenSpace.Notification.Field.BODY, and then add the button using MyOpenSpace.Notification.Field.BUTTONS.The button has to be placed in an array, so if you have more than one button, you’d add each one to the array. Omitting the BUTTONS parameter or passing in an empty array would just attach no buttons to the message. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  17. 90 Chapter 5 Communication and Viral Features Figure 5.9 The notification in the recipient’s Mail Center page The notification is then sent off using a recipient ID, the notification object, and a callback.The recipient can be a single ID or an array of IDs, up to a maximum of ten. The callback behaves exactly like the other callbacks mentioned earlier, so we won’t go into detail. A sent notification will appear in the recipient’s Mail Center page; see Figure 5.9 for exactly how it’ll look. Tip Notifications use the permission MyOpenSpace.Permission.VIEWER_SEND_ NOTIFICATIONS. You may want to use opensocial.hasPermission (followed possibly by opensocial.requestPermission) to check that permission before attempting to send the message. See Chapter 3 to learn how to check and request permissions. Summary The primary source of growth for most apps is friend-to-friend advertising. A user installs the app and then invites a few friends, or a posting appears in the Friend Updates feed with a link to the app. Either way, the app developer has written various activities, messages, and invitations as a way of advertising and seeding the application. It’s important to remember that while these tools must be used, they should never be abused. An app that’s spammy will quickly annoy users, leaving you with few installs and a declining user base. Note Code listings and/or code examples for this chapter can be found on our Google Code page under http://opensocialtictactoe.googlecode.com. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  18. 6 Mashups and External Server Communications Theclever things. Sometimes other people get tolots oftheir smart ideas. Sometimessmart Web is a big place. A very big place.With smart people doing lots of and use your needs are so specific that you have to write your own services.Whatever your needs, you will likely reach a point where the “out-of-the-box” offerings from OpenSocial on MySpace are just not enough to satisfy your needs.Thankfully, OpenSocial recognizes these needs and provides you with a mechanism or two for communicating with external servers. In this chapter we’ll add two different features to our app that are dependent on external server communications. Each feature will use a different technique.We will make use of existing services on the Web to create a “mashup”-style app. Communication with your own servers, and securing those channels, will be covered when we discuss other styles of applications. Communicating with External Servers What Is an External Server? An external server is any server whose DNS address does not resolve to the same top-level domain as the main hosting page. The Web browser imposes multiple security constraints when dealing with an external server, particularly with regard to cookies and XMLHttpRequest (XHR) calls. In the case of apps, an external server can also be considered any server that is not under the control of MySpace. The two notions are close enough to be interchangeable for most discussions in this book. The main MySpace top-level domain is myspace.com, but all apps are hosted in the domain msappspace.com, also referred to as a “jail domain” since it restricts apps’ access to the parent page via the same-origin policy regarding source domains. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  19. 92 Chapter 6 Mashups and External Server Communications OpenSocial recognizes that it can’t be all things to all people. In fact, it’s designed to be just some things to all people—namely, an API for exposing social information.To that end it really is designed for use in external applications and mashups. There are a multitude of techniques for communicating with external servers. If all you are doing is referencing static content, there are almost no constraints. If you want to do something a little more dynamic, like invoke a Web service, things are a little more complicated. As we said before, static content on external servers has very little in the way of con- straints. So long as you use a fully qualified address, the image file will resolve from any server.This is a common technique for large Web sites.They make use of a content delivery network, or CDN. A CDN may be simple or complex. A simple CDN just offloads the bandwidth that would be used to serve static content from the dynamic app servers, leaving more bandwidth and processing power for handling dynamic requests. Most browsers also throttle the number of concurrent connections back to a single domain, so this technique allows the browser to download more files at once; therefore the page loads faster. Dynamic content is another story.There are a handful of well-established techniques for creating dynamic content, some legitimate, some nefarious.We’ll cover the well- established techniques here and touch on the nefarious ones in Chapter 13, Performance, Scaling, and Security. Mashups Origin of Mashups A mashup is a Web site or Web application that seamlessly combines content from more than one source into an integrated experience. The first mashups were simply hackers reverse-engineering the map APIs from companies like Yahoo! and MapQuest to make interesting overlays, such as laundromats near you. Over time, the mashup was recog- nized as not cannibalizing business but being a new business and application model in the Web 2.0 universe. While direct information is cloudy, the term mashup itself is likely derived from a prac- tice in music where two different-source music tracks are combined, often through digital manipulation, to create something entirely new. An example of this would be mixing Madonna’s “Like a Virgin” vocals over heavy drum and bass instrumentals. Mashups are a combination of one or more services in a new way to make a new service or product that is different from the original. As companies have recognized the value of allowing external parties to use their serv- ices and infrastructure, the number of open APIs catering to mashup-style applications has proliferated widely. Several new business models have emerged, allowing larger Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
  20. Adding a Feed Reader to Our App 93 providers to leverage their services and infrastructure for new revenue streams by providing so-called cloud services to third parties.This is in sharp contrast to the reaction to what we’ll call “proto-mashups” from the early days of the Web. Back then it was common practice for preportal aggregation sites to either deep-link to buried serv- ices within another site (for example, linking to buying concert tickets via TicketMaster from a band review site) or completely hijack a competitor’s content by using framesets to make their site look like the competitor’s. Pitfalls of Deep Linking A number of court cases have resulted in deep linking being declared illegal. The decisions were largely based on the fact that the deep linker/framer (utilizing site) used the content for commercial gain without the consent of the content generator (service site). The practical reasoning is that the utilizing site was using the service site as a nonconsenting content provider and bypassing the service site’s advertising to show the utilizing site’s own ads. This was a contentious issue for some time—so contentious, in fact, that the W3C felt the need to publish a paper arguing that deep linking should be legal since that is one of the major ways information interacts on the Web. In practice, deep linking has been difficult to prosecute. A cease-and-desist letter has been the action of choice for any company attempting to protect its content, and it has usually been successful. Almost every major Internet player has some sort of open API to cater to mashup applications. Content feeds continue to be a major component. As we transition to “Web 2.5/3.0,” consisting of cloud services and user-generated content, a number of new APIs are also emerging. More obvious and pedestrian applications come in the form of hosted databases (like Amazon’s SimpleDB service) and various app-hosting services. Among the newer services are those that help spread the reach of user-generated con- tent across the Web, like Google’s Blogger Data API, Digg’s user ratings, and MySpace’s own PostTo endpoints. Adding a Feed Reader to Our App We’ll now extend our app by adding a feed reader.This feature allows your users to never have to leave their game to keep up with the latest happenings on the Web. In the interest of theatrics, we’ll do this as a contrasting implementation in three parts.We’ll add a standard set of feeds for the user to select from.Then we will demonstrate three differ- ent implementations using makeRequest: n Manual display using the FEED content type n Manual display using the DOM content type n Raw text response of the feed with TEXT content type Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
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