Ted On Flash: AS2 Private Getter/Setter Values and Getter/Setter Private Array Example

AS2 Private Getter/Setter Values and Getter/Setter Private Array Example

DIGG IT! 0 Comments Published Friday, March 12, 2004 at 8:06 AM .

From AS2 it is difficult to use a common function using implicit "function get" & "function set" getter/setter syntax. Using a common function enables private variables within the getter/setter and avoids duplicate variables. The only way to accomplish this is within the AS2 class constructor, unless there is a solution I don't know about.

AS2 example:Source

//class file Widget.as

class Widget {

	//constructor	

	function Widget(d){		

		//define function for both getter and setter

		var f = function(s){

			//reference to the executing function object

			var self = arguments.callee	

			

			//getter

			if(arguments.length <1){

				return self.privateProp

			

			//setter

			}else{

				self.privateProp = s

			}

		}

		//set an inital value via setting the function

		f(d)

		//add a getter/setter to the instance

		addProperty('user',f,f)		

	}

}

Now this is far from perfect as you loose the benefits of strict typing at compile-time but it works. AS2 syntax simply masks the AS1 addProperty method at compile-time. It is unfortunate that you cannot declare a single function for both getter/setter as follows:

function get user = function set user = function(){}

Here is an interesting use of the private getter/setter technique. This getter/setter masks a private array. As you "set" values items are pushed onto the private array and as you "get" the value items are popped off the array and returned. This is an easy way to provide a history as a single property without executing array methods.

Source

f = function(s){

	//reference to the executing function object

	var self = arguments.callee	

	

	//if the array does not exist create it

	if(self.a ==undefined) self.a = []

			

	//getter

	if(arguments.length <1){

		//pop and item off the array

		var r = self.a.pop()

		trace("Undo : " + r)

		//return the value

		return r

			

	//setter

	}else{

		trace("Do : " + s)

		//push an item onto the array

		self.a.push(s)

	}

}

//create the history getter/setter

addProperty('history',f,f)

//delete the reference limiting access through the getter/setter

delete f



history = "Wake Up"

history = "Shower"

history = "Brush Teeth"

history = "Make Bed"

history = "Make Coffee"

history = "Cook Bacon"



// Forgot to get dressed undo 3 steps 

// Simply evaluating the variable pops a value off the private array

history

history

history



history = "Get Dressed"

history = "Make Bed"

history = "Make Coffee"

history = "Cook Bacon"



// I shouldn't have gotten up today

history

history

history

history

history

history

history