The Error class contains information about an error that occurred in a script. In developing ActionScript 3.0 applications, when you run your compiled code in the debugger version of a Flash runtime, a dialog box displays exceptions of type Error, or of a subclass, to help you troubleshoot the code. You create an Error object by using the
Error
constructor function. Typically, you throw a new Error object from within a
try
code block that is caught by a
catch
code block.
You can also create a subclass of the Error class and throw instances of that subclass.
Public Properties
Property Defined By constructor : ObjectA reference to the class object or constructor function for a given object instance.
Object errorID : int[read-only] Contains the reference number associated with the specific error message.
Error message : StringContains the message associated with the Error object.
Error name : StringContains the name of the Error object.
ErrorerrorID:int
[read-only]
Language Version: ActionScript 3.0 Runtime Versions: AIR 1.0, Flash Player 9, Flash Lite 4Contains the reference number associated with the specific error message. For a custom Error object, this number is the value from the id
parameter supplied in the constructor.
Implementation
public function get errorID():int
public var message:String
Language Version: ActionScript 3.0 Runtime Versions: AIR 1.0, Flash Player 9, Flash Lite 4
Contains the message associated with the Error object. By default, the value of this property is "Error
". You can specify a message
property when you create an Error object by passing the error string to the Error
constructor function.
Related API Elements
public var name:String
Language Version: ActionScript 3.0 Runtime Versions: AIR 1.0, Flash Player 9, Flash Lite 4
Contains the name of the Error object. By default, the value of this property is "Error
".
Related API Elements
public function Error(message:String = "", id:int = 0)
Language Version: ActionScript 3.0 Runtime Versions: AIR 1.0, Flash Player 9, Flash Lite 4
Creates a new Error object. If message
is specified, its value is assigned to the object's Error.message
property.
message:String
(default = "
")
— A string associated with the Error object; this parameter is optional. id:int
(default = 0
)
— A reference number to associate with the specific error message.
Related API Elements
The following example creates a new Error object
err
and then, using the
Error()
constructor, assigns the string
"New Error Message"
to
err
.
var err:Error = new Error(); trace(err.toString()); // Error err = new Error("New Error Message"); trace(err.toString()); // Error: New Error Message
public function getStackTrace():String
Language Version: ActionScript 3.0 Runtime Versions: AIR 1.0, Flash Player 9, Flash Lite 4
Returns the call stack for an error at the time of the error's construction as a string. As shown in the following example, the first line of the return value is the string representation of the exception object, followed by the stack trace elements:
TypeError: Error #1009: Cannot access a property or method of a null object reference at com.xyz::OrderEntry/retrieveData()[/src/com/xyz/OrderEntry.as:995] at com.xyz::OrderEntry/init()[/src/com/xyz/OrderEntry.as:200] at com.xyz::OrderEntry()[/src/com/xyz/OrderEntry.as:148]
The preceding listing shows the value of this method when called in a debugger version of Flash Player or code running in the AIR Debug Launcher (ADL). When code runs in a release version of Flash Player or AIR, the stack trace is provided without the file path and line number information, as in the following example:
TypeError: Error #1009: Cannot access a property or method of a null object reference at com.xyz::OrderEntry/retrieveData() at com.xyz::OrderEntry/init() at com.xyz::OrderEntry()
For Flash Player 11.4 and earlier and AIR 3.4 and earlier, stack traces are only available when code is running in the debugger version of Flash Player or the AIR Debug Launcher (ADL). In non-debugger versions of those runtimes, calling this method returns null
.
String
— A string representation of the call stack. override public function toString():String
Language Version: ActionScript 3.0 Runtime Versions: AIR 1.0, Flash Player 9, Flash Lite 4
Returns the string "Error"
by default or the value contained in the Error.message
property, if defined.
Related API Elements
The following example creates a new Error object
err
and then, using the
Error()
constructor, assigns the string
"New Error Message"
to
err
. Finally, the
message
property is set to
"Another New Error Message"
, which overwrites
"New Error Message"
.
var err:Error = new Error(); trace(err.toString()); // Error err = new Error("New Error Message"); trace(err.toString()); // Error: New Error Message err.message = "Another New Error Message"; trace(err.toString()); // Error: Another New Error Message
The following example uses the
ErrorExample
class to show how a custom error can be generated. This is accomplished with the following steps:
nullArray
of Array type is declared, but notice that a new Array object is never created.push()
method within an error handling code segment that catches a custom error by using the CustomError
class, which extends Error
.trace()
statement.package { import flash.display.Sprite; public class ErrorExample extends Sprite { private var nullArray:Array; public function ErrorExample() { try { nullArray.push("item"); } catch(e:Error) { throw new CustomError("nullArray is null"); } } } } class CustomError extends Error { public function CustomError(message:String) { super(message); } }
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