Higher Order Functions in Objective-C

The project is trying to implement higher order functions with similar manners in Swift standard library. Currently Map, Filter, Reduce, Contains, ForEach and FlatMap with/without class restrictor have been implemented for NSArray.

Map:

Iterate an array and applies the same block operation to each element in it.

Without class restrictor

[array map:^id(id obj) { return [(NSString *)obj uppercaseString]; }]

With class restrictor

[array map:^id(id obj) { return [(NSString *)obj uppercaseString]; } class:[NSString class]]

Filter:

Iterate an array and return elements that meet a condition.

Without class restrictor

[array filter:^BOOL(id obj) { return [(NSString *)obj isEqualToString:@"o"]; }]

With class restrictor

[array filter:^BOOL(id obj) { return [(NSString *)obj isEqualToString:@"o"]; } class:[NSString class]]

Reduce:

Combine all elements in an array to create a single output.

Without class restrictor

[array reduce:@"Hey, " block:^id(id obj1, id obj2) { return [NSString stringWithFormat:@"%@%@", obj1, obj2]; }]

With class restrictor

[array reduce:@"Hey, " block:^id(id obj1, id obj2) { return [NSString stringWithFormat:@"%@%@", obj1, obj2]; } class:[NSString class]]

Contains:

Iterate an array and check if any element satisfies a condition.

Without class restrictor

[array contains:^BOOL(id obj) { return [(NSString *)obj isEqualToString:@"H"]; }]

With class restrictor

[array contains:^BOOL(id obj) { return [(NSString *)obj isEqualToString:@"H"]; } class:[NSString class]]

ForEach:

A short-hand for the for loop.

Without class restrictor

[array forEach:^(id obj) { NSLog(@"%@", obj); } ]

With class restrictor

[array forEach:^(id obj) { NSLog(@"%@", obj); } class:[NSString class]]

FlatMap:

Flatten an array of arrays.

Without class restrictor

[array flatMap:^id(id obj) { return obj; }]

With class restrictor

[array flatMap:^id(id obj) { return obj; } class:[NSString class]]