Map, filter and reduce in Objective-C/Cocoa
-------------------------------------------

This is a category to add Python like map, filter and reduce methods to Cocoa NSArray:

    @interface NSArray (Functional)
    
    - (NSArray *)filterUsingSelector:(SEL)aSelector, ...;
    - (NSArray *)mapUsingSelector:(SEL)aSelector, ...;
    - (id)reduceUsingSelector:(SEL)aSelector;
    
    @end

You can then program in functional style:

    NSArray *a = [NSArray arrayWithObjects:@"a", @"ab", @"abc", @"bc", @"c", nil];
    
    NSArray *x = [a filterUsingSelector:@selector(hasPrefix:), @"a", nil];
    NSArray *y = [a mapUsingSelector:@selector(uppercaseString), nil];
    NSArray *z = [a reduceUsingSelector:@selector(stringByAppendingString:)];

Results:

    x: (a, ab, abc)
    y: (A, AB, ABC, BC, C)
    z: aababcbcc

Read the blog post talking about it: http://seriot.ch/blog.php?article=20090109 .