Flash: ActionScript Language Reference- P9

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Flash: ActionScript Language Reference- P9

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  1. String.length Availability Flash Player 5. Usage my_str.length:Number Description Property; an integer specifying the number of characters in the specified String object. Because all string indexes are zero-based, the index of the last character for any string x is x.length - 1. Example The following example creates a new String object and uses String.length to count the number of characters: var my_str:String = "Hello world!"; trace(my_str.length); // output: 12 The following example loops from 0 to my_str.length. The code checks the characters within a string, and if the string contains the @ character, true displays in the Output panel. If it does not contain the @ character, then false displays in the Output panel. function checkAtSymbol(my_str:String):Boolean { for (var i = 0; i
  2. String.slice() Availability Flash Player 5. Usage my_str.slice(start:Number, [end:Number]) : String Parameters start A number; the zero-based index of the starting point for the slice. If start is a negative number, the starting point is determined from the end of the string, where -1 is the last character. end A number; an integer that is 1+ the index of the ending point for the slice. The character indexed by the end parameter is not included in the extracted string. If this parameter is omitted, String.length is used. If end is a negative number, the ending point is determined by counting back from the end of the string, where -1 is the last character. Returns A string; a substring of the specified string. Description Method; returns a string that includes the start character and all characters up to, but not including, the end character. The original String object is not modified. If the end parameter is not specified, the end of the substring is the end of the string. If the character indexed by start is the same as or to the right of the character indexed by end, the method returns an empty string. Example The following example creates a variable, my_str, assigns it a String value, and then calls the slice() method using a variety of values for both the start and end parameters. Each call to slice() is wrapped in a trace() statement that displays the output in the Output panel. // Index values for the string literal // positive index: 0 1 2 3 4 // string: L o r e m // negative index: -5-4-3-2-1 var my_str:String = "Lorem"; // slice the first character trace("slice(0,1): "+my_str.slice(0, 1)); // output: slice(0,1): L trace("slice(-5,1): "+my_str.slice(-5, 1)); // output: slice(-5,1): L // slice the middle three characters trace("slice(1,4): "+my_str.slice(1, 4)); // slice(1,4): ore trace("slice(1,-1): "+my_str.slice(1, -1)); // slice(1,-1): ore // slices that return empty strings because start is not to the left of end trace("slice(1,1): "+my_str.slice(1, 1)); // slice(1,1): trace("slice(3,2): "+my_str.slice(3, 2)); // slice(3,2): trace("slice(-2,2): "+my_str.slice(-2, 2)); // slice(-2,2): 802 Chapter 2:
  3. // slices that omit the end parameter use String.length, which equals 5 trace("slice(0): "+my_str.slice(0)); // slice(0): Lorem trace("slice(3): "+my_str.slice(3)); // slice(3): em An example is also in the Strings.fla file in the HelpExamples folder. The following list gives typical paths to this folder: • Windows: \Program Files\Macromedia\Flash MX 2004\Samples\HelpExamples\ • Macintosh: HD/Applications/Macromedia Flash MX 2004/Samples/HelpExamples/ • See also String.substr(), String.substring() String.slice() 803
  4. String.split() Availability Flash Player 5. Usage my_str.split("delimiter":String, [limit:Number]) : Number Parameters delimiter A string; the character or string at which my_str splits. limit A number; the number of items to place into the array. This parameter is optional. Returns An array; an array containing the substrings of my_str. Description Method; splits a String object into substrings by breaking it wherever the specified delimiter parameter occurs and returns the substrings in an array. If you use an empty string ("") as a delimiter, each character in the string is placed as an element in the array. If the delimiter parameter is undefined, the entire string is placed into the first element of the returned array. Example The following example returns an array with five elements: var my_str:String = "P,A,T,S,Y"; var my_array:Array = my_str.split(","); for (var i = 0; i
  5. /* output: J o e */ An example is also in the Strings.fla file in the HelpExamples folder. The following list gives typical paths to this folder: • Windows: \Program Files\Macromedia\Flash MX 2004\Samples\HelpExamples\ • Macintosh: HD/Applications/Macromedia Flash MX 2004/Samples/HelpExamples/ • See Also Array.join() String.split() 805
  6. String.substr() Availability Flash Player 5. Usage my_str.substr(start:Number, [length:Number]) : String Parameters start A number; an integer that indicates the position of the first character in my_str to be used to create the substring. If start is a negative number, the starting position is determined from the end of the string, where the -1 is the last character. length A number; the number of characters in the substring being created. If length is not specified, the substring includes all the characters from the start to the end of the string. Returns A string; a substring of the specified string. Description Method; returns the characters in a string from the index specified in the start parameter through the number of characters specified in the length parameter. The substr method does not change the string specified by my_str; it returns a new string. Example The following example creates a new string, my_str and uses substr() to return the second word in the string; first, using a positive start parameter, and then using a negative start parameter: var my_str:String = new String("Hello world"); var mySubstring:String = new String(); mySubstring = my_str.substr(6,5); trace(mySubstring); // output: world mySubstring = my_str.substr(-5,5); trace(mySubstring); // output: world An example is also in the Strings.fla file in the HelpExamples folder. The following list gives typical paths to this folder: • Windows: \Program Files\Macromedia\Flash MX 2004\Samples\HelpExamples\ • Macintosh: HD/Applications/Macromedia Flash MX 2004/Samples/HelpExamples/ • 806 Chapter 2:
  7. String.substring() Availability Flash Player 5. Usage my_str.substring(start:Number, [end:Number]) : String Parameters start A number; an integer that indicates the position of the first character of my_str used to create the substring. Valid values for start are 0 through String.length - 1. If start is a negative value, 0 is used. end A number; an integer that is 1+ the index of the last character in my_str to be extracted. Valid values for end are 1 through String.length. The character indexed by the end parameter is not included in the extracted string. If this parameter is omitted, String.length is used. If this parameter is a negative value, 0 is used. Returns String: a substring of the specified string. Description Method; returns a string comprising the characters between the points specified by the start and end parameters. If the end parameter is not specified, the end of the substring is the end of the string. If the value of start equals the value of end, the method returns an empty string. If the value of start is greater than the value of end, the parameters are automatically swapped before the function executes and the original value is unchanged. Example The following example shows how to use substring(): var my_str:String = "Hello world"; var mySubstring:String = my_str.substring(6,11); trace(mySubstring); // output: world The following example shows what happens if a negative start parameter is used: var my_str:String = "Hello world"; var mySubstring:String = my_str.substring(-5,5); trace(mySubstring); // output: Hello An example is also in the Strings.fla file in the Examples folder. The following list gives typical paths to this folder: • Windows: \Program Files\Macromedia\Flash MX 2004\Samples\HelpExamples\ • Macintosh: HD/Applications/Macromedia Flash MX 2004/Samples/HelpExamples/ • String.substring() 807
  8. String.toLowerCase() Availability Flash Player 5. Usage my_str.toLowerCase() : String Parameters None. Returns A string. Description Method; returns a copy of the String object, with all uppercase characters converted to lowercase. The original value is unchanged. Example The following example creates a string with all uppercase characters and then creates a copy of that string using toLowerCase() to convert all uppercase characters to lowercase characters: var upperCase:String = "LOREM IPSUM DOLOR"; var lowerCase:String = upperCase.toLowerCase(); trace("upperCase: " + upperCase); // output: upperCase: LOREM IPSUM DOLOR trace("lowerCase: " + lowerCase); // output: lowerCase: lorem ipsum dolor An example is also in the Strings.fla file in the HelpExamples folder. The following list gives typical paths to this folder: • Windows: \Program Files\Macromedia\Flash MX 2004\Samples\HelpExamples\ • Macintosh: HD/Applications/Macromedia Flash MX 2004/Samples/HelpExamples/ • See Also String.toUpperCase() 808 Chapter 2:
  9. String.toUpperCase() Availability Flash Player 5. Usage my_str.toUpperCase() : String Parameters None. Returns A string. Description Method; returns a copy of the String object, with all lowercase characters converted to uppercase. The original value is unchanged. Example The following example creates a string with all lowercase characters and then creates a copy of that string using toUpperCase(): var lowerCase:String = "lorem ipsum dolor"; var upperCase:String = lowerCase.toUpperCase(); trace("lowerCase: " + lowerCase); // output: lowerCase: lorem ipsum dolor trace("upperCase: " + upperCase); // output: upperCase: LOREM IPSUM DOLOR An example is also found in the Strings.fla file in the HelpExamples folder. The following list gives typical paths to this folder: • Windows: \Program Files\Macromedia\Flash MX 2004\Samples\HelpExamples\ • Macintosh: HD/Applications/Macromedia Flash MX 2004/Samples/HelpExamples/ • See also String.toLowerCase() String.toUpperCase() 809
  10. CHAPTER 2 ActionScript Language Reference " " (string delimiter) Availability Flash Player 4. Usage "text" Parameters text A sequence of zero or more characters. Returns Nothing. Description String delimiter; when used before and after characters, quotation marks ("") indicate that the characters have a literal value and are considered a string, not a variable, numerical value, or other ActionScript element. Example The following example uses quotation marks ("") to indicate that the value of the variable yourGuess is the literal string "Prince Edward Island" and not the name of a variable. The value of province is a variable, not a literal; to determine the value of province, the value of yourGuess must be located. var yourGuess:String = "Prince Edward Island"; submit_btn.onRelease = function() { trace(yourGuess); }; // displays Prince Edward Island in the Output panel See also String class, String() 810 Chapter 2: ActionScript Language Reference
  11. CHAPTER 2 ActionScript Language Reference super Availability Flash Player 6. Usage super.method([arg1, ..., argN]) super([arg1, ..., argN]) Parameters method The method to invoke in the superclass. arg1 Optional parameters that are passed to the superclass version of the method (syntax 1) or to the constructor function of the superclass (syntax 2). Returns Both forms invoke a function. The function can return any value. Description Operator: the first syntax style can be used within the body of an object method to invoke the superclass version of a method and can optionally pass parameters (arg1 ... argN) to the superclass method. This is useful for creating subclass methods that add behavior to superclass methods but also invoke the superclass methods to perform their original behavior. The second syntax style can be used within the body of a constructor function to invoke the superclass version of the constructor function and can optionally pass parameters to it. This is useful for creating a subclass that performs additional initialization but also invokes the superclass constructor to perform superclass initialization. Example In the following example, you create two classes. You use the super keyword in the Sock class to call functions in the parent class (Clothes). Although both the Socks and Clothes classes have a method called getColor(), using super lets you specifically reference the base class’s methods and properties. Create a new AS file called Clothes.as, and enter the following code: class Clothes { private var color:String; function Clothes(param_color) { this.color = param_color; trace("[Clothes] I am the constructor"); } function getColor():String { trace("[Clothes] I am getColor"); return this.color; } function setColor(param_color:String):Void { this.color = param_color; trace("[Clothes] I am setColor"); } } super 811
  12. Then create a new class called Socks that extends the Clothes class, as shown in the following example: class Socks extends Clothes { private var color:String; function Socks(param_color:String) { this.color = param_color; trace("[Socks] I am the constructor"); } function getColor():String { trace("[Socks] I am getColor"); return super.getColor(); } function setColor(param_color:String):Void { this.color = param_color; trace("[Socks] I am setColor"); } } Then create a new AS or FLA file and enter the following ActionScript in the document: import Socks; var mySock:Socks = new Socks("maroon"); trace(" -> "+mySock.getColor()); mySock.setColor("Orange"); trace(" -> "+mySock.getColor()); The following result is displayed in the Output panel: [Clothes] I am the constructor [Socks] I am the constructor [Socks] I am getColor [Clothes] I am getColor -> maroon [Socks] I am setColor [Socks] I am getColor [Clothes] I am getColor -> Orange If you forgot to put the super keyword in the Sock class’s getColor() method, then the getColor() method could call itself repeatedly, which would cause the script to fail because of infinite recursion problems. The Output panel would display the following error if you didn’t use the super keyword: [Socks] I am getColor [Socks] I am getColor ... [Socks] I am getColor 256 levels of recursion were exceeded in one action list. This is probably an infinite loop. Further execution of actions has been disabled in this movie. 812 Chapter 2: ActionScript Language Reference
  13. CHAPTER 2 ActionScript Language Reference switch Availability Flash Player 4. Usage switch (expression){ caseClause: [defaultClause:] } Parameters expression Any expression. caseClause A case keyword followed by an expression, a colon, and a group of statements to execute if the expression matches the switch expression parameter using strict equality (===). defaultClause A default keyword followed by statements to execute if none of the case expressions match the switch expression parameter strict equality (===). Returns Nothing. Description Statement; creates a branching structure for ActionScript statements. As with the if statement, the switch statement tests a condition and executes statements if the condition returns a value of true. All switch statements should include a default case. The default case should include a break statement that prevents a fall-through error if another case is added later. When a case falls through, it doesn’t have a break statement. Example In the following example, if the String.fromCharCode(Key.getAscii()) parameter evaluates to A, the trace() statement that follows case "A" executes; if the parameter evaluates to a, the trace() statement that follows case "a" executes; and so on. If no case expression matches the String.fromCharCode(Key.getAscii()) parameter, the trace() statement that follows the default keyword executes. var listenerObj:Object = new Object(); listenerObj.onKeyDown = function() { switch (String.fromCharCode(Key.getAscii())) { case "A" : trace("you pressed A"); break; case "a" : trace("you pressed a"); break; case "E" : case "e" : trace("you pressed E or e"); break; case "I" : switch 813
  14. case "i" : trace("you pressed I or i"); break; default : trace("you pressed some other key"); } }; Key.addListener(listenerObj); See also === (strict equality), break, case, default, if 814 Chapter 2: ActionScript Language Reference
  15. CHAPTER 2 ActionScript Language Reference System.capabilities object Availability Flash Player 6. Description You can use the System.capabilities object to determine the abilities of the system and player hosting a SWF file, which lets you tailor content for different formats. For example, the screen of a cell phone (black and white, 100 square pixels) is different than the 1000-square-pixel color PC screen. To provide appropriate content to as many users as possible, you can use the System.capabilities object to determine the type of device a user has. You can then either specify to the server to send different SWF files based on the device capabilities or tell the SWF file to alter its presentation based on the capabilities of the device. You can send capabilities information using a GET or POST HTTP method. The following example shows a server string for a computer that has MP3 support, 1600 x 1200 pixel resolution, is running Windows XP, and Flash Player 7 (7.0.19.0): "A=t&SA=t&SV=t&EV=t&MP3=t&AE=t&VE=t&ACC=f&PR=t&SP=t&SB=f&DEB=t&V=WIN%207%2C0%2 C19%2C0&M=Macromedia%20Windows&R=1600x1200&DP=72&COL=color&AR=1.0&OS=Window s%20XP&L=en&PT=External&AVD=f&LFD=f&WD=f" Property summary for the System.capabilities object All properties of the System.capabilities object are read-only. Property Description Server string System.capabilities.avHardwareDisable Specifies whether the user’s camera and AVD microphone are enabled or disabled. System.capabilities.hasAccessibility Indicates whether the player is running on a ACC system that supports communication between Flash Player and accessibility aids. System.capabilities.hasAudio Indicates whether the player is running on a A system that has audio capabilities. System.capabilities.hasAudioEncoder Indicates whether the player is running on a AE system that can encode an audio stream, such as that coming from a microphone. System.capabilities.hasEmbeddedVideo Indicates whether the player is running on a EV system that supports embedded video. System.capabilities.hasMP3 Indicates whether the player is running on a MP3 system that has an MP3 decoder. System.capabilities.hasPrinting Indicates whether the player is running on a PR system that supports printing. System.capabilities object 815
  16. Property Description Server string System.capabilities.hasScreenBroadcast Indicates whether the player supports the SB development of screen broadcast applications to be run through the Flash Communication Server. System.capabilities.hasScreenPlayback Indicates whether the player supports the SP playback of screen broadcast applications that are being run through the Flash Communication Server. System.capabilities.hasStreamingAudio Indicates whether the player can play SA streaming audio. System.capabilities.hasStreamingVideo Indicates whether the player can play SV streaming video. System.capabilities.hasVideoEncoder Indicates whether the player can encode a VE video stream, such as that coming from a web camera. System.capabilities.isDebugger Indicates whether the player is an officially DEB released version or a special debugging version. System.capabilities.language Indicates the language of the system on L which the player is running. System.capabilities.localFileReadDisable Specifies whether the player will attempt to LFD read anything (including the first SWF file the player launches with) from the user’s hard disk. System.capabilities.manufacturer Indicates the manufacturer of Flash Player. M System.capabilities.os Indicates the operating system hosting OS Flash Player. System.capabilities.pixelAspectRatio Indicates the pixel aspect ratio of the screen. AR System.capabilities.playerType Indicates the type of player: stand-alone, PT external, plug-in, or ActiveX. System.capabilities.screenColor Indicates whether the screen is color, COL grayscale, or black and white. System.capabilities.screenDPI Indicates the dots-per-inch screen DP resolution, in pixels. System.capabilities.screenResolutionX Indicates the horizontal size of the screen. R System.capabilities.screenResolutionY Indicates the vertical size of the screen. R System.capabilities.serverString A URL-encoded string that specifies values n/a for each System.capabilities property. System.capabilities.version A string containing Flash Player version and V platform information. 816 Chapter 2: ActionScript Language Reference
  17. System.capabilities.avHardwareDisable Availability Flash Player 7. Usage System.capabilities.avHardwareDisable:Boolean Description Read-only property; a Boolean value that specifies whether access to the user’s camera and microphone has been administratively prohibited (true) or allowed (false). The server string is AVD. Example The following example traces the value of this read-only property: trace(System.capabilities.avHardwareDisable); See also Camera.get(), Microphone.get(), System.showSettings() System.capabilities.avHardwareDisable 817
  18. System.capabilities.hasAccessibility Availability Flash Player 6. Usage System.capabilities.hasAccessibility:Boolean Description Read-only property: a Boolean value that is true if the player is running in an environment that supports communication between Flash Player and accessibility aids; false otherwise. The server string is ACC. Example The following example traces the value of this read-only property: trace(System.capabilities.hasAccessibility); See also Accessibility.isActive(), Accessibility.updateProperties(), _accProps 818 Chapter 2: ActionScript Language Reference
  19. System.capabilities.hasAudio Availability Flash Player 6. Usage System.capabilities.hasAudio:Boolean Description Read-only property: a Boolean value that is true if the player is running on a system that has audio capabilities; false otherwise. The server string is A. Example The following example traces the value of this read-only property: trace(System.capabilities.hasAudio); System.capabilities.hasAudio 819
  20. System.capabilities.hasAudioEncoder Availability Flash Player 6. Usage System.capabilities.hasAudioEncoder:Boolean Description Read-only property: a Boolean value that is true if the player can encode an audio stream, such as that coming from a microphone; false otherwise. The server string is AE. Example The following example traces the value of this read-only property: trace(System.capabilities.hasAudioEncoder); 820 Chapter 2: ActionScript Language Reference
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