Ruby's inject method in Objective-C

Enumerable.h

// Enumerable.h

#import <Foundation/Foundation.h>

typedef id (^InjectBlock)(id, id);

@interface NSArray (Enumerable)
- (id) inject:(id) initial block:(InjectBlock) block;
@end


// Enumerable.m

#import "Enumerable.h"

@implementation NSArray (Enumerable)

- (id) inject:(id) initial block:(InjectBlock) block {
  id memo = initial;
  if (!memo)
    memo = [self objectAtIndex: 0];

  for (id obj in self) {
    memo = block(memo, obj);
  }

  return memo;
}

@end


// main.m

#import "Enumerable.h"

int main(int argc, char *argv[]) {
  NSArray *ary = [NSArray arrayWithObjects: @"cat", @"sheep", @"bear", nil];
  InjectBlock block = ^ id (id memo, id word) {
    return ((NSString *)memo).length > ((NSString *)word).length ? memo : word;
  };

  id longestWord = [ary inject: nil block: block];
  NSLog(@"Longest word %@", longestWord);
}