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:

import flash.utils.ByteArray;

function clone(source:Object):*
{
    var myBA:ByteArray = new ByteArray();
    myBA.writeObject(source);
    myBA.position = 0;
    return(myBA.readObject());
}