简单的开关按钮实现

ToggleButton.h

//
//  ToggleButton.h
//  FaceDemo
//
//  Created by syxc on 15/10/31.
//  Copyright © 2015年 syxc. All rights reserved.
//

#import <UIKit/UIKit.h>


/*!
 * 开关按钮
 */
@interface ToggleButton : UIButton

@property (assign, nonatomic, getter=isOn) BOOL on;

@property (strong, nonatomic) UIImage *offStateImage;
@property (strong, nonatomic) UIImage *onStateImage;

- (void)toggle;

@end

ToggleButton.m

//
//  ToggleButton.m
//  FaceDemo
//
//  Created by syxc on 15/10/31.
//  Copyright © 2015年 syxc. All rights reserved.
//

#import "ToggleButton.h"


@interface ToggleButton ()
- (void)touchedUpInside:(UIButton *)sender;
@end

@implementation ToggleButton

@synthesize on            = _on;
@synthesize offStateImage = _offStateImage;
@synthesize onStateImage  = _onStateImage;

- (instancetype)init {
  self = [super init];
  if (self) {
    [self setup];
  }
  return self;
}

- (instancetype)initWithFrame:(CGRect)frame {
  self = [super initWithFrame:frame];
  if (self) {
    [self setup];
  }
  return self;
}

- (void)awakeFromNib {
  [super awakeFromNib];
  [self setup];
}

- (void)setup {
  self.offStateImage = [self imageForState:UIControlStateNormal];
  self.onStateImage = [self imageForState:UIControlStateSelected];
  
  [self addTarget:self action:@selector(touchedUpInside:) forControlEvents:UIControlEventTouchUpInside];
}

- (void)touchedUpInside:(UIButton *)sender {
  [self toggle];
}

- (void)toggle {
  [self setOn:!_on];
}

- (void)setOn:(BOOL)on {
  _on = on;
  [self setSelected:_on];
  if (on) {
    [self setImage:self.onStateImage forState:(UIControlStateSelected)];
  } else {
    [self setImage:self.offStateImage forState:(UIControlStateNormal)];
  }
}

@end