An extension for NSArray adding functional programming methods to NSArray using blocks.
Using Objective-C blocks, this category adds filter, map and reduce functionality to NSArray, similar to the ones found in Python.
The FilterMapReduce category adds three methods to NSArray.
filter: returns an array containing the elements of the array for which block(obj) evaluates to true.
- (NSArray*)filter:(BOOL (^)(id obj))block;map: calls block(obj) on each of the elements and returns an array of the results.
- (NSArray*)map:(id (^)(id obj))block;reduce:withInitializer: reduces the array to a single value by calling block(obj, current) cumulatively on each element from left to right and using the result as current for the next element. An initializer is given for the first value of current.
- (id)reduce:(id (^)(id obj, id current))block withInitializer:(id<NSCopying>)initializer;NSArray* numbers = @[@1, @2, @3, @4, @5, @6, @7, @8, @9, @10];
// Returns (2, 4, 6, 8, 10)
NSArray* evenNumbers = [numbers filter:^BOOL(id obj) { return ([obj integerValue] % 2 == 0); }];
// Returns (1, 4, 9, 16, 25, 36, 49, 64, 81, 100)
NSArray* squares = [numbers map:^id(id obj) { return @([obj integerValue] * [obj integerValue]); }];
// Returns 55
NSNumber* sum = [numbers reduce:^id(id obj, id current) { return @([obj integerValue] + [current integerValue]); }
withInitializer:@0];Copyright © 2013 Charles Francoise
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