将NSArray过滤到objective-c中的新NSArray中 [英] filtering NSArray into a new NSArray in objective-c

问题描述

我有一个 NSArray ，我想用原始数组中的对象创建一个新的 NSArray 符合一定标准。该标准由返回 BOOL 的函数决定。

I have an NSArray and I'd like to create a new NSArray with objects from the original array that meet certain criteria. The criteria is decided by a function that returns a BOOL.

我可以创建一个 NSMutableArray ，遍历源数组并复制过滤器函数接受的对象，然后创建一个不可变的版本。

I can create an NSMutableArray, iterate through the source array and copy over the objects that the filter function accepts and then create an immutable version of it.

有更好的方法吗？

推荐答案

NSArray 和 NSMutableArray 提供了过滤数组内容的方法。 NSArray 提供 filteredArrayUsingPredicate：，它返回包含接收器中与指定谓词匹配的对象的新数组。 NSMutableArray 添加 filterUsingPredicate：，它根据指定的谓词评估接收者的内容，只留下匹配的对象。这些方法如下例所示。

NSArray and NSMutableArray provide methods to filter array contents. NSArray provides filteredArrayUsingPredicate: which returns a new array containing objects in the receiver that match the specified predicate. NSMutableArray adds filterUsingPredicate: which evaluates the receiver’s content against the specified predicate and leaves only objects that match. These methods are illustrated in the following example.

NSMutableArray *array =
    [NSMutableArray arrayWithObjects:@"Bill", @"Ben", @"Chris", @"Melissa", nil];

NSPredicate *bPredicate =
    [NSPredicate predicateWithFormat:@"SELF beginswith[c] 'b'"];
NSArray *beginWithB =
    [array filteredArrayUsingPredicate:bPredicate];
// beginWithB contains { @"Bill", @"Ben" }.

NSPredicate *sPredicate =
    [NSPredicate predicateWithFormat:@"SELF contains[c] 's'"];
[array filterUsingPredicate:sPredicate];
// array now contains { @"Chris", @"Melissa" }

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