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Copyright (c) 1994 by NeXT Computer, Inc. All Rights Reserved.


Inherits From: NSObject

Conforms To: NSCoding, NSCopying, NSMutableCopying NSObject (NSObject)

Declared In: Foundation/NSArray.h

Class Description

The NSArray class declares the programmatic interface to an object that manages an immutable array of objects. (The complementary class NSMutableArray manages modifiable arrays of objects.) NSArray's two primitive methodscount and objectAtIndex:provide the basis for all the other methods in its interface. The count method returns the number of elements in the array. objectAtIndex: gives you access to the array elements by index, with index values starting at 0.

The methods objectEnumerator and reverseObjectEnumerator also permit sequential access of the elements of the array, differing only in the direction of travel through the elements. These methods are provided so that array objects can be traversed in a manner similar to that used for objects of other collection classes, such as NSDictionary.

Generally, you instantiate an NSArray by sending one of the array... messages to the NSArray class object. These methods return an NSArray containing the elements you pass in as arguments. (Note that arrays can't contain nil objects.) These objects aren't copied; rather, each object receives a retain message before it's added to the array. When an object is removed from an array, it's sent a release message.

NSArray provides methods for querying the elements of the array. indexOfObject: searches the array for the object that matches its argument. To determine whether the search is successful, each element of the array is sent an isEqual: message, as declared in the NSObject protocol. Another method, indexOfObjectIdenticalTo:, is provided for the less common case of determining whether a specific object is present in the array. indexOfObjectIdenticalTo: tests each element in the array to see whether its id matches that of the argument.

NSArray's makeObjectsPerform: and makeObjectsPerform:withObject: methods let you act on the individual objects in the array by sending them messages. To act on the array as a whole, a variety of methods are defined. You can create a sorted version of the array (sortedArrayUsingSelector: and sortedArrayUsingFunction:context:), extract a subset of the array (subarrayWithRange:), or concatenate the elements of an array of NSString objects into a single string (componentsJoinedByString:). In addition, you can compare two array objects using the isEqualToArray: and firstObjectCommonWithArray: methods.

Allocating and Initializing an Array

Querying the Array

Sending Messages to Elements

Comparing Arrays

Deriving New Arrays

Joining String Elements

Creating a String Description of the Array