CapoPlaybackButton.h

//
//  CapoPlaybackButton.h
//  Capo
//
//  Created by Christopher Liscio on 9/22/10.
//  Copyright (c) 2010 SuperMegaUltraGroovy. All rights reserved.
//

#import <UIKit/UIKit.h>

enum {
    kCapoPlaybackButtonStatePause = (1 << 16),
    kCapoPlaybackButtonStatePlay  = (1 << 17),
};

@interface CapoPlaybackButton : UIButton {
}

@property (nonatomic,assign) NSInteger playbackState;

@end

CapoPlaybackButton.m

//
//  CapoPlaybackButton.m
//  Capo
//
//  Created by Christopher Liscio on 9/22/10.
//  Copyright (c) 2010 SuperMegaUltraGroovy. All rights reserved.
//

#import "CapoPlaybackButton.h"

static void *kPlaybackStateObservingContext = &kPlaybackStateObservingContext;

@implementation CapoPlaybackButton

@synthesize playbackState;

- (void)awakeFromNib {
    [self setImage:[UIImage imageNamed:@"PauseN"] forState:( kCapoPlaybackButtonStatePause )];
    [self setImage:[UIImage imageNamed:@"PauseP"] forState:( kCapoPlaybackButtonStatePause | UIControlStateHighlighted )];
    
    [self setImage:[UIImage imageNamed:@"PlayN"] forState:( kCapoPlaybackButtonStatePlay )];
    [self setImage:[UIImage imageNamed:@"PlayP"] forState:( kCapoPlaybackButtonStatePlay | UIControlStateHighlighted )];    
    
    NSAssert( kCapoPlaybackButtonStatePause & UIControlStateApplication, @"Custom state not within UIControlStateApplication" );
    NSAssert( kCapoPlaybackButtonStatePlay & UIControlStateApplication, @"Custom state not within UIControlStateApplication" );
    
    [self addObserver:self forKeyPath:@"playbackState" options:NSKeyValueObservingOptionOld context:kPlaybackStateObservingContext];
}

- (UIControlState)state {
    NSInteger returnState = [super state];
    return ( returnState | self.playbackState );
}

- (void)dealloc {
    [self removeObserver:self forKeyPath:@"playbackState"];
    [super dealloc];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    if ( context == kPlaybackStateObservingContext ) {
        NSInteger oldState = [[change objectForKey:NSKeyValueChangeOldKey] integerValue];
        if ( oldState != self.playbackState ) {
            [self layoutSubviews];
        }
    }
    else {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}

@end