Delegation.m

if ([delegate respondsToSelector:@selector(fooController:didBar:baz:qux:)]) {
  [delegate fooController:self 
                   didBar:@"barbarian"
                      baz:@"buzzbuzz"
                      qux:@"wtfreally?"];
}

// vs.

[[delegate ifResponds] fooController:self 
                              didBar:@"barbarian" 
                                 baz:@"buzzbuzz"
                                 qux:@"wtfreally?"];

Functional.m

id sliced = [self slice:NSMakeRange(0, [words count] - 1)];
id mapped = [[sliced map] stringByAppendingString:@" "];
id arr = [mapped arrayByAddingObject:[[words lastObject]
                                      stringByAppendingString:@"."]];
id sentence = [arr inject:^id(id memo, id obj) {
  return [memo stringByAppendingString:obj];
}];

NSLog(@"sentence: %@", sentence);
// => "sentence: Dogs are pretty freaking awesome."

Imperative.m

NSArray *words = [NSArray arrayWithObjects:
                  @"Dogs",@"are",
                  @"pretty",@"freaking",
                  @"awesome",nil];
                  
NSMutableString *sentence = [[NSMutableString alloc] init];
for (NSInteger i = 0; i < [words count]; i++) {
  NSString *rawWord = [words objectAtIndex:i];
  NSString *word = (i < ([words count] - 1))
                    ? [rawWord stringByAppendingString:@" "]
                    : [rawWord stringByAppendingString:@"!"];
  [sentence appendString:word];
}

NSLog(@"sentence: %@", sentence);
// => "sentence: Dogs are pretty freaking awesome."

JSKit-Conditional.m

id str = @"dog";
BOOL go = YES;
[[str ifTrue:go] doSomethingStringlike];

// or

[str ifTrue:go do:^(id obj) {
  [obj doSomethingStringlike];
}];

JSRespondsProxy.m

@implementation JSRespondsProxy

- forwardingTargetForSelector:(SEL)aSelector {
  return [[self target] ifTrue:
          [[self target] respondsToSelector:aSelector]];
}

- (void)forwardInvocation:(NSInvocation *)invocation {
  [[invocation ifTrue:
    [[self target] respondsToSelector:[invocation selector]]]
   invokeWithTarget:[self target]];
}

- (BOOL)respondsToSelector:(SEL)aSelector {
  return YES;
}

- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {
  NSMethodSignature *signature = [[[self target] ifTrue:
                                   [[self target] respondsToSelector:aSelector]]
                                  methodSignatureForSelector:aSelector];
  
  if (signature == nil){
    SEL dummySelector = @selector(class);
    signature = [NSObject methodSignatureForSelector:dummySelector];
  }
  
  return signature;
}

@end

JSTargetedProxy.m

@implementation JSTargetedProxy
@synthesize target;

- initWithTarget:aTarget {
  if (self != nil) {
    [self setTarget:aTarget];
  } return self;
}

+ proxyWithTarget:aTarget {
  return [[self alloc] initWithTarget:aTarget];
}

@end

NSArray+Functional.h

@interface NSArray (Functional)
- (void)each:(void (^)(id obj))aBlock;
- (void)eachInvocation:(NSInvocation *)invocation;
- each;

- map:(id (^)(id obj))aBlock;
- mapInvocation:(NSInvocation *)invocation;
- map;

- inject:(id (^)(id memo, id obj))aBlock;
- slice:(NSRange)aRange;

- join;
- join:sep;
@end

NSArray+Functional.m

- inject:(id (^)(id memo, id obj))aBlock {
  __block id accumulator = [self objectAtIndex:0];
  
  [[self slice:NSMakeRange(1, [self count] - 1)] each:^(id obj) {
    accumulator = aBlock(accumulator,obj);
  }];
  
  return accumulator;
}

- slice:(NSRange)aRange {
  NSIndexSet *indexes = [NSIndexSet indexSetWithIndexesInRange:aRange];
  return [self objectsAtIndexes:indexes];
}

- join {
  return [self join:@""];
}

- join:sep {
  return [self componentsJoinedByString:sep];
  /**
   This is how it would be done if Cocoa didn't have this built-in:
   ****************************************************************
   id sliced = [self slice:NSMakeRange(0, [self count] - 1)];
   id mapped = [[sliced map] stringByAppendingString:sep];
   id arr = [mapped arrayByAddingObject:[self lastObject]];
   return [arr inject:^id(id memo, id obj) { return [memo stringByAppendingString:obj]; }];
   **/
}

NSObject+Conditionals.m

@implementation NSObject (Conditionals)

#pragma mark -
#pragma mark JSRespondsProxy

- ifResponds {
  return [JSRespondsProxy proxyWithTarget:self];
}

- ifTrue:(BOOL)condition {
  return condition ? self : nil;
}

- ifFalse:(BOOL)condition {
  return !condition ? self : nil;
}

- (void)ifTrue:(BOOL)condition do:(void (^)(id obj))aBlock {
  if (condition) aBlock(self);
}

- (void)ifFalse:(BOOL)condition do:(void (^)(id obj))aBlock {
  return [self ifTrue:!condition do:aBlock];
}

@end

Smalltalk-Conditional.st

str := 'dog'.
go := true.
go ifTrue:[
  str doSomethingStringlike.
].