ios开发——实用技术篇&Block／KVO／通知／代理

 1 什么是Block：从C的声明符到Objective-C的Blocks语法
 2 块代码以闭包得形式将各种内容进行传递，可以是代码，可以是数组无所不能。块代码十分方便将不同地方的代码集中统一，使其易读性增强。
 3 
 4 来看这里怎么进行数组传递。
 5 
 6 typedef void (^Arr_Block)(NSArray *array);
 7 
 8 - (void)showArrayUsingBlock:(Arr_Block)block
 9 {
10     NSDictionary *dict = @{@"array": @[@"Chelsea", @"MUFC", @"Real Madrid"]};
11     NSArray *array = dict[@"array"];
12     block(array);
13 }
14 
15 调用方法，显示
16 
17 - (IBAction)blockCallBack
18 {
19     [self showArrayUsingBlock:^(NSArray *array) {
20         _outputLabel.text = array[1];
21     }];
22 }
23 
24 三种模式都很轻松~

 1  1 .person类 
 2 @implementation Person 
 3 @synthesize name,age;//属性name 将被监视 
 4 -(void) changeName 
 5 { 
 6     name=@"changeName directly"; 
 7 } 
 8 @end 
 9  
10  
11 2.PersonMonitor类  监视了name属性 
12 @implementation PersonMonitor 
13  
14 - (void)observeValueForKeyPath:(NSString *)keyPath 
15                       ofObject:(id)object 
16                         change:(NSDictionary *)change 
17                        context:(void *)context 
18 { 
19     if ([keyPath isEqual:@"name"]) 
20     { 
21         NSLog(@"change happen, old:%@   new:%@",[change objectForKey:NSKeyValueChangeOldKey],[change objectForKey:NSKeyValueChangeNewKey]); 
22     } 
23 } 
24 @end 
25  
26  
27 3测试代码 
28  
29    //初始化被监视对象 
30     Person *p =[[Person alloc] init]; 
31    //监视对象 
32    PersonMonitor *pm= [[PersonMonitor alloc]init]; 
33     [p addObserver:pm forKeyPath:@"name" options:(NSKeyValueObservingOptionNew |NSKeyValueObservingOptionOld) context:nil]; 
34    
35 //测试前的数据 
36     NSLog(@"p.name is %@",p.name); 
37     
38 //通过setvalue 的方法，PersonMonitor的监视将被调用 
39   [p setValue:@"name kvc" forKey:@"name"]; 
40   
41 //查看设置后的值 
42    NSLog(@"p name get by kvc is %@",[p valueForKey:@"name"]); 
43  
44 //效果和通过setValue 是一致的     
45 p.name=@"name change by .name="; 
46  
47  //通过person自己的函数来更改name  
48      [p changeName];  
49  
50  结果是 
51 输出 
52 2011-07-03 16:35:57.406 Cocoa[13970:903] p.name is name 
53 2011-07-03 16:35:57.418 Cocoa[13970:903] change happen, old:name   new:name kvc 
54 2011-07-03 16:35:57.420 Cocoa[13970:903] p name get by kvc is name kvc 
55 2011-07-03 16:35:57.421 Cocoa[13970:903] change happen, old:name kvc   new:name change by .name= 

 1 通知中心的方式可以不用设置代理，但是需要设置观察者和移除观察者。
 2 
 3 
 4 
 5 代码
 6 
 7 - (IBAction)callBack
 8 {
 9     NSDictionary *dict = @{@"array": @[@"Chelsea", @"MUFC", @"Real Madrid"]};
10     NSArray *array = dict[@"array"];
11     [[NSNotificationCenter defaultCenter] postNotificationName:@"OutputArrayNotification" object:array];
12 }
13 
14 注册和移出观察者
15 
16 - (void)viewWillAppear:(BOOL)animated
17 {
18     [super viewWillAppear:animated];
19     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(outputWithNote:) name:@"OutputArrayNotification" object:nil];
20 }
21 
22 - (void)viewDidDisappear:(BOOL)animated
23 {
24     [super viewDidDisappear:animated];
25     [[NSNotificationCenter defaultCenter] removeObserver:self name:@"OutputArrayNotification" object:nil];
26 }
27 
28 显示
29 
30 - (void)outputWithNote:(NSNotification *)aNotification
31 {
32     NSArray *receiveArray = [aNotification object];
33     _outputLabel.text = receiveArray[0];
34 }

 1 作为IOS中最常见的通讯模式，代理几乎无处不在。
 2 
 3 
 4 
 5 看实例
 6 这里有一个数组，我们首先通过代理的方式将数组传递到其他方法中去。
 7 设置协议及方法
 8 
 9 @protocol CallBackDelegate;
10 
11 @interface ViewController : UIViewController
12 @property (weak, nonatomic) id<CallBackDelegate> delegate;
13 @end
14 
15 @protocol CallBackDelegate <NSObject>
16 - (void)showArrayWithDelegate:(NSArray *)array;
17 @end
18 
19 @interface ViewController () <CallBackDelegate>
20 
21 点击按钮传递数组让其显示
22 
23 - (IBAction)delegateCallBack
24 {
25     NSDictionary *dict = @{@"array": @[@"Chelsea", @"MUFC", @"Real Madrid"]};
26     NSArray *array = dict[@"array"];
27     [self.delegate showArrayWithDelegate:array];
28 }
29 
30 调用，显示
31 
32 - (void)showArrayWithDelegate:(NSArray *)array
33 {
34     _outputLabel.text = array[2];
35 }
36 
37 最重要也是最容易忽略的，就是一定要设置delegate的指向。
38 完成后屏幕显示