Package	system.evaluators
Class	public class PropertyEvaluator
Inheritance	PropertyEvaluator Object
Implements	Evaluable
Subclasses	ConfigEvaluator, LocaleEvaluator

Evaluates a type string expression and return the property value who corresponding in the target object specified in this evaluator.

Example :

     import system.evaluators.PropertyEvaluator ;
     
     var obj:Object =
     {
         message : "hello world" ,
         title   : "my title"    ,
         menu    :
         {
             title : "my menu title" ,
             label : "my label"
         }
     }
     
     var evaluator:PropertyEvaluator = new PropertyEvaluator( obj ) ;
     
     // valid expressions
     
     trace( evaluator.eval( "message"    ) ) ; // hello world
     trace( evaluator.eval( "title"      ) ) ; // my title
     trace( evaluator.eval( "menu.title" ) ) ; // my menu title
     trace( evaluator.eval( "menu.label" ) ) ; // my label
     
     // invalid expressions
     
     trace( evaluator.eval( ""            ) ) ; // null
     trace( evaluator.eval( "unknow"      ) ) ; // null
     trace( evaluator.eval( "menu.unknow" ) ) ; // null
     
     // change the "undefineable" value returns in the eval() method when the evaluation failed.
     
     evaluator.undefineable = "empty" ;
     trace( evaluator.eval( "unknow" ) ) ; // empty ;
     
     evaluator.undefineable = undefined ;
     trace( evaluator.eval( "unknow" ) ) ; // undefined ;
         
     // activate the throwError mode.
         
     evaluator.throwError = true ;
     
     try
     {    
         evaluator.eval( "test" ) ;
     }
     catch( e:Error )
     {
         trace( e ) ; // EvalError: [object PropertyEvaluator] eval failed with the expression : test
     }
     

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