Object  - AS3

A reference to the class object or constructor function for a given object instance. If an object is an instance of a class, the constructor property holds a reference to the class object. If an object is created with a constructor function, the constructor property holds a reference to the constructor function. Do not confuse a constructor function with a constructor method of a class. A constructor function is a Function object used to create objects, and is an alternative to using the class keyword for defining classes.

If you use the class keyword to define a class, the class's prototype object is assigned a property named constructor that holds a reference to the class object. An instance of the class inherits this property from the prototype object. For example, the following code creates a new class, A, and a class instance named myA:

     dynamic class A {}
     trace(A.prototype.constructor);      // [class A]
     trace(A.prototype.constructor == A); // true
     var myA:A = new A();
     trace(myA.constructor == A);         // true

Advanced users may choose to use the function keyword instead of the class keyword to define a Function object that can be used as a template for creating objects. Such a function is called a constructor function because you can use it in conjunction with the new operator to create objects. If you use the function keyword to create a constructor function, its prototype object is assigned a property named constructor that holds a reference to the constructor function. If you then use the constructor function to create an object, the object inherits the constructor property from the constructor function's prototype object. For example, the following code creates a new constructor function, f, and an object named myF:

     function f() {}
     trace(f.prototype.constructor);      // function Function() {}
     trace(f.prototype.constructor == f); // true
     var myF = new f();
     trace(myF.constructor == f);         // true

Note: The constructor property is writable, which means that user code can change its value with an assignment statement. Changing the value of the constructor property is not recommended, but if you write code that depends on the value of the constructor property, you should ensure that the value is not reset. The value can be changed only when the property is accessed through the prototype object (for example, className.prototype.constructor).

If you access the constructor property and compile in strict mode, you will get an error at compile time because the constructor property depends on the protoype object, which is a runtime entity. If you use standard mode or if the class description specifies "dynamic", the code runs without generating an error.

Related API Elements

A reference to the prototype object of a class or function object. The prototype property is automatically created and attached to any class or function object that you create. This property is static in that it is specific to the class or function that you create. For example, if you create a class, the value of the prototype property is shared by all instances of the class and is accessible only as a class property. Instances of your class cannot directly access the prototype property.

A class's prototype object is a special instance of that class that provides a mechanism for sharing state across all instances of a class. At run time, when a property is not found on a class instance, the delegate, which is the class prototype object, is checked for that property. If the prototype object does not contain the property, the process continues with the prototype object's delegate checking in consecutively higher levels in the hierarchy until the Flash runtime finds the property.

Note: In ActionScript 3.0, prototype inheritance is not the primary mechanism for inheritance. Class inheritance, which drives the inheritance of fixed properties in class definitions, is the primary inheritance mechanism in ActionScript 3.0.

Creates an Object object and stores a reference to the object's constructor method in the object's constructor property.

Indicates whether an object has a specified property defined. This method returns true if the target object has a property that matches the string specified by the name parameter, and false otherwise. The following types of properties cause this method to return true for objects that are instances of a class (as opposed to class objects):

• Fixed instance properties—variables, constants, or methods defined by the object's class that are not static;
• Inherited fixed instance properties—variables, constants, or methods inherited by the object's class;
• Dynamic properties—properties added to an object after it is instantiated (outside of its class definition). To add dynamic properties, the object's defining class must be declared with the dynamic keyword.

The following types of properties cause this method to return false for objects that are instances of a class:

• Static properties—variables, constants, or methods defined with the static keyword in an object's defining class or any of its superclasses;
• Prototype properties—properties defined on a prototype object that is part of the object's prototype chain. In ActionScript 3.0, the prototype chain is not used for class inheritance, but still exists as an alternative form of inheritance. For example, an instance of the Array class can access the valueOf() method because it exists on Object.prototype, which is part of the prototype chain for the Array class. Although you can use valueOf() on an instance of Array, the return value of hasOwnProperty("valueOf") for that instance is false.

ActionScript 3.0 also has class objects, which are direct representations of class definitions. When called on class objects, the hasOwnProperty() method returns true only if a property is a static property defined on that class object. For example, if you create a subclass of Array named CustomArray, and define a static property in CustomArray named foo, a call to CustomArray.hasOwnProperty("foo") returns true. For the static property DESCENDING defined in the Array class, however, a call to CustomArray.hasOwnProperty("DESCENDING") returns false.

Note: Methods of the Object class are dynamically created on Object's prototype. To redefine this method in a subclass of Object, do not use the override keyword. For example, A subclass of Object implements function hasOwnProperty():Boolean instead of using an override of the base class.

Parameters

Indicates whether an instance of the Object class is in the prototype chain of the object specified as the parameter. This method returns true if the object is in the prototype chain of the object specified by the theClass parameter. The method returns false if the target object is absent from the prototype chain of the theClass object, and also if the theClass parameter is not an object.

Note: Methods of the Object class are dynamically created on Object's prototype. To redefine this method in a subclass of Object, do not use the override keyword. For example, A subclass of Object implements function isPrototypeOf():Boolean instead of using an override of the base class.

Parameters

Indicates whether the specified property exists and is enumerable. If true, then the property exists and can be enumerated in a for..in loop. The property must exist on the target object because this method does not check the target object's prototype chain.

Properties that you create are enumerable, but built-in properties are generally not enumerable.

Note: Methods of the Object class are dynamically created on Object's prototype. To redefine this method in a subclass of Object, do not use the override keyword. For example, A subclass of Object implements function propertyIsEnumerable():Boolean instead of using an override of the base class.

Parameters

Sets the availability of a dynamic property for loop operations. The property must exist on the target object because this method does not check the target object's prototype chain.

Parameters

Related API Elements

Returns the string representation of this object, formatted according to locale-specific conventions.

The default implementation of this method does not perform locale-specific formatting and returns the same string as toString(). Subclasses should provided their own locale-aware implementation when appropriate.

Note: Methods of the Object class are dynamically created on Object's prototype. To redefine this method in a subclass of Object, do not use the override keyword. For example, a subclass of Object implements function toLocaleString():String instead of using an override of the base class.

Related API Elements

Returns the string representation of the specified object.

Note: Methods of the Object class are dynamically created on Object's prototype. To redefine this method in a subclass of Object, do not use the override keyword. For example, a subclass of Object implements function toString():String instead of using an override of the base class.

Returns the primitive value of the specified object. If this object does not have a primitive value, the object itself is returned.

Note: Methods of the Object class are dynamically created on Object's prototype. To redefine this method in a subclass of Object, do not use the override keyword. For example, A subclass of Object implements function valueOf():Object instead of using an override of the base class.

Related API Elements

The example creates the value objects firstInitObj and secondInitObj. The custom class Circle accepts the value object and loops over it while setting its matching internal properties to those defined in the value object.

package {
    import flash.display.Sprite;

    public class ObjectExample extends Sprite {
        public function ObjectExample() {
            var firstInitObj:Object = new Object();
            firstInitObj.bgColor = 0xFF0000;
            firstInitObj.radius = 25;
            firstInitObj.xCenter = 25;
            firstInitObj.yCenter = 25;
                        
            var firstCircle:Circle = new Circle(firstInitObj);
            addChild(firstCircle);
            firstCircle.x = 50;
            firstCircle.y = 50;

            var secondInitObj:Object = {bgColor:0xCCCCCC, radius:50, xCenter:50, yCenter:50};

            var secondCircle:Circle = new Circle(secondInitObj);            
            addChild(secondCircle);
            secondCircle.x = 100;
            secondCircle.y = 100;
        }
        
    }
}

import flash.display.Shape;
    
class Circle extends Shape {
    public var bgColor:Number = 0xFFFFFF;
    public var radius:Number = 0;
    public var xCenter:Number = 0;
    public var yCenter:Number = 0;
        
    public function Circle(initObj:Object) {
        for(var i:String in initObj) {
            this[i] = initObj[i];
        }
        draw();
    }
        
    public function draw():void {
        graphics.beginFill(bgColor);
        graphics.drawCircle(xCenter, yCenter, radius);
        graphics.endFill();
    }
}