iOS之代理/协议 @protocal

 1 #import <UIKit/UIKit.h>
 2 
 3 //声明协议passValueDelegate
 4 @protocol passValueDelegate <NSObject>
 5 
 6 -(void)myPassValue:(NSString*)msg;
 7 -(void)myCallback;
 8 
 9 @end
10 
11 //ViewController类使用上面定义的协议，并将实现协议中的两个方法
12 @interface ViewController : UIViewController<passValueDelegate>{
13     
14 }
15 
16 //ViewController自己保有了一个passValueDelegate的协议对象
17 //类似UITableView类中保有了两个delegate/dataSource协议对象
18 @property NSObject<passValueDelegate> *mDelegate;
19 
20 -(void)callMeToDo;
21 
22 @end

 1 #import "ViewController.h"
 2 #import "BViewController.h"
 3 
 4 @interface ViewController ()
 5 
 6 @end
 7 
 8 @implementation ViewController
 9 
10 - (void)viewDidLoad {
11     [super viewDidLoad];
12 
13     //写了一个按钮，点击跳转到BViewController上
14     UIButton *button = [[UIButton alloc]initWithFrame:CGRectMake(100, 100, 80, 50)];
15     button.layer.backgroundColor = [UIColor greenColor].CGColor;
16     [button addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside];
17     [self.view addSubview:button];
18 }
19 
20 //此处是代码将会调用_mDelegate对象的实现的方法。具体可以看后面的代码。
21 -(void)callMeToDo{
22     [_mDelegate myPassValue:@"cool"];
23     [_mDelegate myCallback];
24 }
25 
26 -(void)buttonPressed:(id)sender{
27     BViewController *bvc = [[BViewController alloc]init];
28     //ViewController自己实现了这个协议，
29     // 然后bvc就可以引用ViewController的对象，回调ViewContrller中实现的两个方法。
30     bvc.myDelegate =  self;
31     [self presentViewController:bvc animated:YES completion:nil];
32 }
33 
34 //ViewContrller使用协议，并强制实现的2个方法
35 -(void)myPassValue:(NSString*)msg{
36     NSLog(@"%@", msg);
37 }
38 
39 -(void)myCallback{
40     NSLog(@"callback call now..");
41 }
42 
43 - (void)didReceiveMemoryWarning {
44     [super didReceiveMemoryWarning];
45     // Dispose of any resources that can be recreated.
46 }
47 
48 @end

1 #import <UIKit/UIKit.h>
2 #import "ViewController.h"
3 
4 @interface BViewController : UIViewController
5 
6 //保有一个使用了passValueDelegate协议的对象
7 @property NSObject<passValueDelegate> *myDelegate;
8 
9 @end

 1 #import "BViewController.h"
 2 
 3 @interface BViewController ()
 4 
 5 @end
 6 
 7 @implementation BViewController
 8 
 9 - (void)viewDidLoad {
10     [super viewDidLoad];
11     // Do any additional setup after loading the view from its nib.
12 }
13 
14 - (IBAction)buttonPressed:(id)sender {
15     //按钮点击，回调ViewController中实现的方法。
16     //（有点和block类似。都是可以向前回调，但是本质不同）
17     //（block是函数的引用，而协议则是对象多态的表现。）
18     [_myDelegate myCallback];
19     [_myDelegate myPassValue:@"Message from B_View_Controller"];
20     
21 }
22 
23 - (void)didReceiveMemoryWarning {
24     [super didReceiveMemoryWarning];
25     // Dispose of any resources that can be recreated.
26 }
27 
28 @end

1 #import <UIKit/UIKit.h>
2 #import "ViewController.h"
3 
4 //使用ViewController中的协议passValueDelegate
5 @interface CViewController : UIViewController<passValueDelegate>
6 
7 @end

 1 #import "CViewController.h"
 2 
 3 @interface CViewController ()
 4 
 5 @end
 6 
 7 @implementation CViewController
 8 
 9 - (void)viewDidLoad {
10     [super viewDidLoad];
11     // Do any additional setup after loading the view from its nib.
12 }
13 
14 -(void)myPassValue:(NSString *)msg{
15     NSLog(@"C:%@", msg);
16 }
17 
18 -(void)myCallback{
19     NSLog(@"C callback.");
20 }
21 
22 - (void)didReceiveMemoryWarning {
23     [super didReceiveMemoryWarning];
24     // Dispose of any resources that can be recreated.
25 }
26 
27 @end

1 #import <UIKit/UIKit.h>
2 #import "ViewController.h"
3 
4 //使用passValueDelegate协议
5 @interface DViewController : UIViewController<passValueDelegate>
6 
7 @end

 1 #import "DViewController.h"
 2 
 3 @interface DViewController ()
 4 
 5 @end
 6 
 7 @implementation DViewController
 8 
 9 - (void)viewDidLoad {
10     [super viewDidLoad];
11     // Do any additional setup after loading the view from its nib.
12 }
13 
14 //既然使用了协议，就要实现协议的方法。
15 -(void)myCallback{
16     NSLog(@"this is D vc");
17 }
18 
19 -(void)myPassValue:(NSString *)msg{
20     NSLog(@"i am D viewcontroller");
21 }
22 
23 
24 - (IBAction)buttonPress:(id)sender {
25     //点击按钮，创建ViewController(可以理解为创建一个UITableView对象)
26     ViewController* vc = [[ViewController alloc]init];
27     //绑定代理
28     vc.mDelegate = self;
29     //主动回调。（可以理解为tableview中的reload函数，主动reload）
30     [vc callMeToDo];
31     //总结上面的代码：tableview可以不用主动回调，
32     // 因为tableview是一个控件，控件是一个监听者，他可以根据点击交互来发起对协议函数的回调。
33     //上面是为了举例，所以使用了主动的回调。
34 }
35 
36 - (void)didReceiveMemoryWarning {
37     [super didReceiveMemoryWarning];
38     // Dispose of any resources that can be recreated.
39 }
40 
41 @end