Vector class: creating typed array lists in ActionScript 3.0
Problem
In some situations we need to be sure whether the correct type of data has been passed within an array list for an argument of a method or has been received from a specific function.
Solution
Using the Vector class we can specify which type of data will be accepted in our list, allowing the insertion if only the type required was matched.
Detailed explanation
package {
public class User {
public var firstname:String = null;
public var lastname:String = null;
public var email:String = null;
public function User():void { }
}
}
2. Create a Flash File (ActionScript 3.0) within the same directory of our ActionScript class, and then type the following code:
var mylist:Vector.<User> = new Vector.<User>();
try {
mylist.push("Hello");
} catch(e:Error) {
trace(e.message);
}
Probably you will get an error message, right? Why? Cause you're trying to insert a String in our list, not a User object.
However, if you try the following:
var mylist:Vector.<User> = new Vector.<User>();
try {
var user:User = new User();
user.firstname = "Jhonatan"; user.lastname = "Rosa Jacinto"; user.email = "foo@foo.com";
mylist.push(user);
trace(mylist[0].firstname);
}
catch(e:Error) {
trace(e.message);
}
You will get "JHONATAN" in the output panel... because the object inserted was an User Object.
Very very simple, right?
One thing... if I had the following code:
var list:Vector.<DisplayObject> = new Vector.<DisplayObject>();
list.push(new MovieClip());
This code will generate an error or not?
The answer is NOO! It will work good! Why? The reason is a MovieClip object is an object of type DisplayObject, cause the MovieClip class extends from the DisplayObject class... so any MovieClip object is a DisplayObject as well.
Following this thinking, the code below will not work:
var list:Vector.<DisplayObject> = new Vector.<DisplayObject>();
list.push(new User());
Why? As explained before, our User class doesn't extend from DisplayObject or MovieClip class. So, it cannot be pushed into our list.
I hope you enjoy this tutorial.
Thanks guys and see you next time! ;)
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