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Commonly Used Array Methods

197

Creating Arrays

The methods in this section are class methods, as denoted by the plus sign

(+). You use class methods to send messages to a class—in this case,

NSArray or NSMutableArray. For more information on class methods, see

“Sending a Message to a Class” (page 172).

+ array

Returns an empty array. Usually used to create NSMutableArrays.

NSArrays created with this method are permanently empty.

// Most common use

id mutableArray = [NSMutableArray array];

// May not be what you want

id array = [NSArray array];

+ arrayWithObject:

Returns an array containing the single speciﬁed object.

+ arrayWithObjects:

Returns an array containing the objects in the argument list. The

argument list is a comma-separated list of objects ending with

nil.

id array = [NSMutableArray arrayWithObjects:

@"Plates", @"Plasticware", @"Napkins", nil];

+ arrayWithArray:

Returns an array containing the contents of a speciﬁed array.

Usually used to create an NSMutableArray from an immutable

NSArray. For example, the following statement creates an

NSMutableArray from a constant NSArray object:

id mutableArray = [NSMutableArray

arrayWithArray:@("A", "B", "C")];

+ arrayWithContentsOfFile:

Returns an array initialized from the contents of a speciﬁed ﬁle.

The speciﬁed ﬁle can be a full or relative pathname; the ﬁle that it

names must contain a string representation of an array, such as that

produced by the

writeToFile:atomically: method.

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Apple WebObjects 3.5 Manual de usuario Pagina 197