ADOBE® FLEX® 3: PROGRAMMING ACTIONSCRIPT™ 3.0

ADOBE FLEX 3

Developer Guide

156

Associative array with an indexed array

To make the individual arrays easier to access, you can use an associative array for the days of the week and an

indexed array for the task lists. Using an associative array allows you to use dot syntax when referring to a particular

day of the week, but at the cost of extra run-time processing to access each element of the associative array. The

following example uses an associative array as the basis of a task list, with a key and value pair for each day of the

week:

var masterTaskList:Object = new Object();

masterTaskList["Monday"] = ["wash dishes", "take out trash"];

masterTaskList["Tuesday"] = ["wash dishes", "pay bills"];

masterTaskList["Wednesday"] = ["wash dishes", "dentist", "wash dog"];

masterTaskList["Thursday"] = ["wash dishes"];

masterTaskList["Friday"] = ["wash dishes", "clean house"];

masterTaskList["Saturday"] = ["wash dishes", "wash car", "pay rent"];

masterTaskList["Sunday"] = ["mow lawn", "fix chair"];

Dot syntax makes the code more readable by making it possible to avoid multiple sets of brackets.

trace(masterTaskList.Wednesday[1]); // output: dentist

trace(masterTaskList.Sunday[0]);// output: mow lawn

You can iterate through the task list using a for..in loop, but you must use bracket notation instead of dot syntax

to access the value associated with each key. Because

masterTaskList is an associative array, the elements are not

necessarily retrieved in the order that you may expect, as the following example shows:

for (var day:String in masterTaskList)

{

trace(day + ": " + masterTaskList[day])

}

/* output:

Sunday: mow lawn,fix chair

Wednesday: wash dishes,dentist,wash dog

Friday: wash dishes,clean house

Thursday: wash dishes

Monday: wash dishes,take out trash

Saturday: wash dishes,wash car,pay rent

Tuesday: wash dishes,pay bills

*/

Cloning arrays

The Array class has no built-in method for making copies of arrays. You can create a shallow copy of an array by

calling either the

concat() or slice() methods with no arguments. In a shallow copy, if the original array has

elements that are objects, only the references to the objects are copied rather than the objects themselves. The copy

points to the same objects as the original does. Any changes made to the objects are reflected in both arrays.

In a deep copy, any objects found in the original array are also copied so that the new array does not point to the same

objects as does the original array. Deep copying requires more than one line of code, which usually calls for the

creation of a function. Such a function could be created as a global utility function or as a method of an Array

subclass.

The following example defines a function named

clone() that does deep copying. The algorithm is borrowed from

a common Java programming technique. The function creates a deep copy by serializing the array into an instance

of the ByteArray class, and then reading the array back into a new array. This function accepts an object so that it

can be used with both indexed arrays and associative arrays, as shown in the following code: