Learning the iOS 4 SDK for JavaScript Programmers

About NSArray

Like JavaScript arrays, a Cocoa Touch array is an ordered collection of data, with each element of the array referenced through a zero-based index number. You can use that index to iterate through both styles in for repeat loops. Although both objects have a handful of methods that perform similar tasks with arrays, you have more restrictions and more possibilities with the NSArray than you do with JavaScript arrays.

The most important departure is that when you create an NSArray, you have one shot to include elements in the instance of the array. That instance remains fixed for its life with respect to its content and order. Methods allow you to create new NSArray instances that append additional elements to the original, extract copies of elements from the array, and obtain a copy of the array sorted according to criteria you devise. To create an array that has the same type of self-modifying behavior as the JavaScript array, you can use the NSMutableArray class.

Arrays are often vital components of iOS apps because they typically become the data sources for table views. You can write an NSArray to a file (or deliver a file in your app bundle) and, in a subsequent session, load that file to recreate the NSArray object for your code to use. The sorted order of an array determines the sorted order of cells in the table view.

The NSArray class is far more adaptable than a C array, whose elements must all be of the same data type. That restriction is gone from NSArray