UI阶段的 Target/Action设计模式

问题:我怎么实现通过点击,一个UIImageView的对象,实现相应的操作,这里以更换图片为例

思路一:仿照UIButton的target/action设计模式
(MFC 手动管理内存)

创建一个类继承UIImageView,来实现该功能
ButtonImageView.h

#import 

@interface ButtonImageView : UIImageView

@property(nonatomic,strong)id target;
@property(nonatomic,assign)SEL action;

- (instancetype)initWithFrame:(CGRect)frame target:(id)target action:(SEL)action;

@end

ButtonImageView.m

#import "ButtonImageView.h"

@implementation ButtonImageView

- (instancetype)initWithFrame:(CGRect)frame target:(id)target action:(SEL)action
{
    //  完整的初始化方法
    self = [super initWithFrame:frame];
    if (self) {
        self.target = target;
        self.action = action;
    }
    return self;
}

//  由于你需要点击,之后有相关的操作
//  重写touches的相关方法

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{

}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{

}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    //  更换图片,只需要点击一下
    //  这里需要用该类的一个对象,去调用该类的方法
    [self.target performSelector:self.action withObject:self];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{

}

创建一个根试图控制器:创建一个根视图控制器对象,赋值给window的跟视图属性

#import “AppDelegate.m”

#import "AppDelegate.h"
#import "RootViewController.h"

@interface AppDelegate ()

@end

@implementation AppDelegate
- (void)dealloc
{
    [_window release];
    [super dealloc];
}


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]]autorelease
    ];
    // Override point for customization after application launch.
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];

    // 设置根视图控制器
    RootViewController *rootVC = [[RootViewController alloc]init];
    self.window.rootViewController = rootVC;
    [rootVC release];



    return YES;
}
@end

RootViewController.m

#import "RootViewController.h"
#import "ButtonImageView.h"


@interface RootViewController ()

@end

@implementation RootViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    UIImage *img = [UIImage imageNamed:@"5.jpg"];
    ButtonImageView *BtnImgView = [[ButtonImageView alloc]initWithFrame:[UIScreen mainScreen].bounds                                      target:self action:@selector(BtnImgViewClick:)];
       BtnImgView.image = img;
    BtnImgView.userInteractionEnabled = YES;
       [self.view addSubview:BtnImgView];
       [BtnImgView release];



}

- (void)BtnImgViewClick:(ButtonImageView *)btnImgView
{
    //  更换图片
    UIImage *img1 = [UIImage imageNamed:@"6.jpeg"];
    btnImgView.image = img1;
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

**小结:
这个模式设计出来的类的对象,就像一个button一样,当你点击该对象后,将返回该类的touchesEnd方法,将你初始化出来的一个对象的target调用该对象的action方法,其实还可以携带参数(withObject:…).参数需不需要,根据你的action方法决定.这样做就是为了降低类和类之间的耦合,从而实现封装和提高代码的复用性功能.**