NSObject+AssociatedObjects.m

//
//  NSObject+AssociatedObjects.m
//  
//  Created by Andy Matuschak on 8/27/09.
//  Public domain 
//
// edited by rebo to add message forwarding, so extended objects can call zero-argument void
// blocks using [instance method] format. 
//
// Not really recommended as this produces "may not respond" warnings in compiler.

#import "NSObject+AssociatedObjects.h"
#import <objc/runtime.h>
#import "typedefs.h"
@implementation NSObject (AMAssociatedObjects)

- (void)associateValue:(id)value withKey:(void *)key
{
	objc_setAssociatedObject(self, key, value, OBJC_ASSOCIATION_RETAIN);
}

- (id)associatedValueForKey:(void *)key
{
	return objc_getAssociatedObject(self, key);
}

- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
{

	SEL sel = @selector(extendedMethodCall:);
    NSMethodSignature * sig ;
  if ( aSelector != sel){
    sig = [[self class] instanceMethodSignatureForSelector:sel];
  } else {
    sig = nil;
  }
  return sig;
} 
  
- (void)forwardInvocation: (NSInvocation *) invocation
{
 
  SEL sel = [invocation selector];
  
  [invocation setArgument: &sel atIndex:2];

  [invocation setSelector: @selector(extendedMethodCall:)];
  return [invocation invokeWithTarget:self];
}

- (void) extendedMethodCall:(SEL)aSelector;
{
  WorkBlk_t  extendedMethod = [self associatedValueForKey:aSelector];
  if (extendedMethod){
    extendedMethod(); 
  }
}

@end

NSObject+StateMachine.m

//
//  NSObject+StateMachine.m

#import "NSObject+StateMachine.h"
#import "NSObject+AssociatedObjects.h"
#import <objc/runtime.h>
#import "typedefs.h"

@implementation NSObject (StateMachine)


- (void)stateMachineExtendInstanceMethods {
  //Mix-in Instance Variables
  //
  //
  NSMutableArray * transitions  = [[NSMutableArray alloc] init];
  NSMutableArray * callbacks    = [[NSMutableArray alloc] init];
	NSString * state        = nil;
	
  objc_setAssociatedObject(self, @selector(transitions), transitions, OBJC_ASSOCIATION_RETAIN);
  objc_setAssociatedObject(self, @selector(callbacks), callbacks, OBJC_ASSOCIATION_RETAIN);
  objc_setAssociatedObject(self, @selector(state), state, OBJC_ASSOCIATION_RETAIN);
  
  //Mix-in Methods
  //
  //
  WorkBlk_t initializeState = ^{ 
  NSLog(@"Initiailizing State ...");
  objc_setAssociatedObject(self, @selector(state), @"INACTIVE", OBJC_ASSOCIATION_RETAIN);
  };
  
  objc_setAssociatedObject(self, @selector(initializeState), [initializeState copy], OBJC_ASSOCIATION_RETAIN);
  
  TransBlk_t addTransition = ^(NSString * transitionName, NSString * startState, NSString * endState){ 
      NSLog(@"Adding Transition  ...");
      SEL transitionSelector =  NSSelectorFromString(transitionName);
      [transitions addObject:[NSDictionary dictionaryWithObjectsAndKeys: transitionName,@"transitionName", startState,@"startState", endState, @"endState",nil]];
  
      WorkBlk_t callTransition = ^{
          NSLog(@"Applying Transition...");
          NSString *state = objc_getAssociatedObject(self, @selector(state));
          if (state == startState){
               objc_setAssociatedObject(self, @selector(state), endState, OBJC_ASSOCIATION_RETAIN);
               
//call backs
               NSMutableArray * callbacks = objc_getAssociatedObject(self, @selector(callbacks));
	       NSUInteger i = [callbacks indexOfObjectPassingTest:^BOOL(id obj, NSUInteger index, BOOL * stop){ if ([obj valueForKey:@"transitionName"]== transitionName){ return YES; }else{return NO;} }];
               if ( i != NSNotFound ){
                    WorkBlk_t callback = [[callbacks objectAtIndex:i] valueForKey:@"callback"];
                   callback();
                   }
           }
      };
      objc_setAssociatedObject(self, transitionSelector , [callTransition copy], OBJC_ASSOCIATION_RETAIN);
  
  return transitionSelector;
  };
  objc_setAssociatedObject(self, @selector(addTransition), [addTransition copy], OBJC_ASSOCIATION_RETAIN);
   
  CallbackBlk_t addCallbackForTransition = ^(NSString * transitionName, WorkBlk_t callback){ 
  NSLog(@"Adding CallBack  ...");
  NSMutableArray * callbacks = objc_getAssociatedObject(self, @selector(callbacks));

  // [transitions addObject:[NSDictionary dictionaryWithObjectsAndKeys: transitionName,@"transitionName", startState,@"startState", endState, @"endState",nil]];
  [callbacks addObject:[NSDictionary dictionaryWithObjectsAndKeys:transitionName,@"transitionName", callback, @"callback",nil]];
  };
  objc_setAssociatedObject(self, @selector(addCallbackForTransition), [addCallbackForTransition copy], OBJC_ASSOCIATION_RETAIN);  
  
}

+(void)stateMachineExtendClassMethods{
  // OK even more stupid stuff
  // By adding a category class method you can add class 'methods' and 'ivars'
  //
  // You can even add pseudo-instance methods on arbitrary classes at run time
  // as shown in the third objc_setAssociatedObject call below


  NSMutableArray * transitions  = [[NSMutableArray alloc] init];
  [transitions addObject:@"foo"];
  objc_setAssociatedObject(self, @selector(transitions), transitions, OBJC_ASSOCIATION_RETAIN);
  
  WorkBlk_t longDescription = ^{ 
  NSLog(@"Here is a long description of the class %@", [self description]);
  };
  objc_setAssociatedObject(self, @selector(longDescription), [longDescription copy], OBJC_ASSOCIATION_RETAIN);
  
    InstanceBlk_t describeInstance = ^(id obj){
      //check obj is right kind of class
      if ([obj isKindOfClass:self]){
        NSLog(@" This is an pseudo-instance method, called on %@", [obj description]);
        } else { NSLog(@"Warning instance is not a %@", [self description]);}
      };
  
  objc_setAssociatedObject(self, @selector(describeInstance), [describeInstance copy], OBJC_ASSOCIATION_RETAIN);
  
  
}

@end

StateMachineAppDelegate.m

//
//  StateMachineAppDelegate.m
//  StateMachine
//
//  
//  CRAZY ATTEMPT TO SEE HOW MUCH I CAN MANGLE objc_setAssociatedObject
//  DO NOT USE THIS CODE:P

// The idea is to add functionality to arbitrary objects
// so one can have ruby extend style behaviour through Objective-c categories

// It works by adding a single category method, within which instance variables and 'method' blocks
// are set up  by making use of objc_setAssociatedObject.

// I wanted to see how easy it would be to use, well it is possible but it is really unwieldy 
// and makes code very hard to read.

// see NSObject+StateMachine.m for the core of the work, it is a dumb partially implemented state machine
// that in theory can be used for any instance of any NSObject.

#import "StateMachineAppDelegate.h"
#import "NSObject+StateMachine.h"
#import "NSObject+AssociatedObjects.h"
#import "typedefs.h"


@implementation StateMachineAppDelegate


@synthesize window;

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
	// Insert code here to initialize your application 
  // StateMachine * sm = [[StateMachine alloc] init];
  NSDictionary * dictStateMachine = [[NSDictionary alloc] init];
  
  [dictStateMachine stateMachineExtendInstanceMethods];  
  
  
  // Initialize State
  WorkBlk_t  initializeState = [dictStateMachine associatedValueForKey:@selector(initializeState)];
  initializeState();

  //Check State
  NSLog(@"Object State is :%@", [dictStateMachine associatedValueForKey:@selector(state)]);
  
  //Add a transition from Inactive to Active
  TransBlk_t selectorByAddingTransition = [dictStateMachine associatedValueForKey:@selector(addTransition)];
  SEL activate = selectorByAddingTransition( @"ACTIVATE", @"INACTIVE", @"ACTIVE");

  // Activate
  WorkBlk_t  activateState = [dictStateMachine associatedValueForKey:activate];
  activateState();

  //Check Final State
  NSLog(@"Object State is :%@", [dictStateMachine associatedValueForKey:@selector(state)]);
  
  
  // Reset and Run Again
  
  NSLog(@"\n\nReseting and Running Again:");
  
  initializeState();
  activateState();
  
  
  NSLog(@"\n\nAdding A Callback to Activate State:");
  // How about a callback when activating
  
  CallbackBlk_t addCallbackToTransition = [dictStateMachine associatedValueForKey:@selector(addCallbackForTransition)];
  addCallbackToTransition(@"ACTIVATE", ^{ NSLog(@"Warning State Has Been Activated!") ;});
  
  
  // Reset and Run Again This time With Call Back In Effect
  NSLog(@"\n\nReseting and Running Again, after callback has been added:");
  initializeState();
  activateState();
  NSLog(@"Object State is :%@", [dictStateMachine associatedValueForKey:@selector(state)]);
  
  NSLog(@"Object With additional methods and state is  a : %@", [dictStateMachine className]);
  
	NSLog(@"\n\n\n Creating New Object");
  NSString * sm = [[NSString alloc] init];
[sm stateMachineExtendInstanceMethods];  
  
  
  // Initialize State
  WorkBlk_t  initializeState_b = [sm associatedValueForKey:@selector(initializeState)];
  initializeState_b();

  //Check State
  NSLog(@"Object State is :%@", [sm associatedValueForKey:@selector(state)]);
  
  //Add a transition from Inactive to Active
  TransBlk_t selectorByAddingTransition_b = [sm associatedValueForKey:@selector(addTransition)];
  SEL activate_b = selectorByAddingTransition_b( @"PAINT", @"INACTIVE", @"PAINTED");

  // Activate
  WorkBlk_t  activateState_b = [sm associatedValueForKey:activate_b];
  activateState_b();

  //Check Final State
  NSLog(@"Object State is :%@", [sm associatedValueForKey:@selector(state)]);
  
  // Reset and Run Again
  
  NSLog(@"\n\nReseting and Running Again:");
  
  initializeState_b();
  activateState_b();
  NSLog(@"Object State is :%@", [sm associatedValueForKey:@selector(state)]);
  
  NSLog(@"\n\nAdding A Callback to Activate State:");
  // How about a callback when activating
  
  CallbackBlk_t addCallbackToTransition_b = [sm associatedValueForKey:@selector(addCallbackForTransition)];
  addCallbackToTransition_b(@"PAINT", ^{ NSLog(@"Hey This Object Has Been Painted!") ;});
  
  
  // Reset and Run Again This time With Call Back In Effect
  NSLog(@"\n\nReseting and Running Again, after callback has been added:");
  initializeState_b();
  activateState_b();
  
  NSLog(@"Object With additional methods and state is  a : %@", [sm className]);


  //added....

  // Can add class instance variables, class methods, and also pseudo-instance methods on arbitrary classes:

[NSArray stateMachineExtendClassMethods];
  
  NSArray * array = [NSArray associatedValueForKey:@selector(transitions)];
  NSLog( @"Class instance array = %@" , array);
  
  WorkBlk_t  longDescription = [NSArray associatedValueForKey:@selector(longDescription)];
  longDescription();
  
  NSArray * arr = [NSArray arrayWithObjects:@"bar",nil];
  
  InstanceBlk_t describeInstance = [NSArray associatedValueForKey:@selector(describeInstance)];
  describeInstance(arr);

}

@end