using a category on C4Shape to access the touches of a shape via the notification center

C4Shape+touchSetAccess.h

//
//  C4Shape+touchSetAccess.h
//  accessTouches
//
//  Created by Travis Kirton on 12-05-12.
//  Copyright (c) 2012 POSTFL. All rights reserved.
//

#import "C4Shape.h"

@interface C4Shape (touchSetAccess)
-(void)postNotification:(NSString *)notification userInfo:(NSDictionary *)userInfo;
@end

C4Shape+touchSetAccess.m

//
//  C4Shape+touchSetAccess.m
//  accessTouches
//
//  Created by Travis Kirton on 12-05-12.
//  Copyright (c) 2012 POSTFL. All rights reserved.
//

#import "C4Shape+touchSetAccess.h"

@implementation C4Shape (touchSetAccess)

-(void)postNotification:(NSString *)notification userInfo:(NSDictionary *)userInfo {
	[[NSNotificationCenter defaultCenter] postNotificationName:notification object:self userInfo:userInfo];
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    NSDictionary *userInfo = [NSDictionary dictionaryWithObject:touches forKey:@"touches"];
    [self postNotification:@"touchesBegan" userInfo:userInfo];
    [super touchesBegan:touches withEvent:event];
    [self touchesBegan];
}

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    NSDictionary *userInfo = [NSDictionary dictionaryWithObject:touches forKey:@"touches"];
    [self postNotification:@"touchesMoved" userInfo:userInfo];
    [super touchesMoved:touches withEvent:event];
    [self touchesMoved];
}

@end

C4WorkSpace.m

//
//  C4WorkSpace.m
//  accessTouches
//
//  Created by Travis Kirton on 12-05-12.
//  Copyright (c) 2012 POSTFL. All rights reserved.
//

#import "C4WorkSpace.h"
@interface C4WorkSpace () 
-(void)accessTouchSet:(NSNotification *)notification;
@end

@implementation C4WorkSpace {
    C4Shape *s;
}

-(void)setup {
    s.animationDuration = 0.0f;
    s = [C4Shape rect:CGRectMake(0, 0, 100, 100)];
    [self.canvas addShape:s];
    
    [[NSNotificationCenter defaultCenter] addObserver:self 
                                             selector:@selector(accessTouchSet:) 
                                                 name:@"touchesMoved" 
                                               object:nil];
}

-(void)accessTouchSet:(NSNotification *)notification {
    NSDictionary *d = [notification userInfo];
    NSSet *touchSet = (NSSet *)[d objectForKey:@"touches"];
    UITouch *t = (UITouch *)[touchSet anyObject];
    CGPoint previousLocation = [t previousLocationInView:self.canvas];
    CGPoint currentLocation = [t locationInView:self.canvas];
    CGPoint displacement = CGPointMake(currentLocation.x - previousLocation.x, currentLocation.y - previousLocation.y);

    C4Shape *currentShape = (C4Shape *)[notification object];
    CGPoint newCenter = currentShape.center;
    newCenter.x += displacement.x;
    newCenter.y += displacement.y;
    currentShape.center = newCenter;
}

@end