A few handy ruby/smalltalk-like list comprehensions.

NSArray+ListComprehensions

typedef BOOL (^BooleanBlock)(id obj); // Returns true or false given an object
typedef id (^ValueBlock)(id obj); // Returns an object given an object (generally of the same type, may or may not be modified)
typedef id (^AccumulatorBlock)(id acc, id obj); // Returns the accumulator object, likely mutated.

// A few ruby-like  list comprehensions.
@implementation NSArray (ListComprehensions)

// Returns the first object for which the block returns true. AKA array.match()
-(id) find:(BooleanBlock)block {
    NSUInteger index = [self indexOfObjectPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) { 
                           return block(obj); 
                        }];
    return ((index == NSNotFound) ? nil : self[index]);
}

// Returns a new array with only selected elements.
-(NSArray *) select:(BooleanBlock)block {
    NSMutableArray *selected = [NSMutableArray array];
    [self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) { 
        if (block(obj)) [selected addObject:obj]; 
    }];
    return (NSArray *)selected;
}

// Iterates over array and returns a new array the same size as the current one. AKA map()
-(NSArray *) map:(ValueBlock)block {
    NSMutableArray *collector = [NSMutableArray arrayWithCapacity:[self count]];
    [self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) { 
        [collector addObject:block(obj)]; 
    }];
    return [collector copy];
}

-(id) reduceFromInitial:(id)value block:(AccumulatorBlock)block {
    __block id acc = value;
    [self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        acc = block(acc, obj);
    }];
    return acc;
}

@end

Or use https://github.com/supermarin/ObjectiveSugar