KVC-KVO:利用KVC-KVO观察者模式实现页面的传值。
K(key)键值 V(value)值 C(change)变化 O(observe)观察
这是OC中的语法:作用当某个对象的值发生变化时,通知某个函数,在函数内部,能够获取到变化的值。
框架中:通知中心。
使用场合:在音乐播放的过程中,如果选择的歌曲发生变化,立刻通知播放器,播放新选择的歌曲。
1 #import "RootViewController.h" 2 #import "DetailViewController.h" 3 @interface RootViewController () 4 { 5 UITableView *tv; 6 DetailViewController *detail; 7 } 8 @property NSString *sendValue; //存放点击某一行的值 9 @end 10 11 @implementation RootViewController 12 13 - (void)viewDidLoad { 14 [super viewDidLoad]; 15 // Do any additional setup after loading the view. 16 17 detail=[[DetailViewController alloc] init]; 18 //添加观察者 19 [self addObserver:detail forKeyPath:@"sendValue" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew context:nil]; 20 21 [self createUI ]; 22 } 23 -(void)createUI{ 24 tv=[[UITableView alloc] initWithFrame:CGRectMake(0, 20, 375, 600) style:UITableViewStylePlain]; 25 tv.delegate=self; 26 tv.dataSource=self; 27 // tv.separatorStyle=UITableViewCellSeparatorStyleSingleLine; 28 [self.view addSubview:tv]; 29 } 30 -(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{ 31 return 30; 32 } 33 -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{ 34 NSString *identifier=@"kvckvo"; 35 UITableViewCell *cell=[tableView dequeueReusableCellWithIdentifier:identifier]; 36 if (!cell) { 37 cell=[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:identifier]; 38 } 39 cell.textLabel.text=[NSString stringWithFormat:@"%ld",indexPath.row+1]; 40 return cell; 41 } 42 -(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{ 43 44 [self presentViewController:detail animated:NO completion:nil]; 45 //赋值操作 46 self.sendValue=[NSString stringWithFormat:@"%ld",indexPath.row+1]; 47 48 } 49 - (void)didReceiveMemoryWarning { 50 [super didReceiveMemoryWarning]; 51 // Dispose of any resources that can be recreated. 52 }
1 #import "DetailViewController.h" 2 @interface DetailViewController () 3 4 @end 5 6 @implementation DetailViewController 7 @synthesize lblData; 8 @synthesize btnReturn; 9 - (void)viewDidLoad { 10 [super viewDidLoad]; 11 // Do any additional setup after loading the view. 12 lblData=[[UILabel alloc] initWithFrame:CGRectMake(100, 100, 100, 30)]; 13 [self.view addSubview:lblData]; 14 btnReturn=[[UIButton alloc] initWithFrame:CGRectMake(100, 150, 100, 30)]; 15 btnReturn.backgroundColor=[UIColor redColor]; 16 [btnReturn setTitle:@"返回" forState:UIControlStateNormal]; 17 [btnReturn addTarget:self action:@selector(btn_Return:) forControlEvents:UIControlEventTouchUpInside]; 18 [self.view addSubview:btnReturn]; 19 } 20 -(void)btn_Return:(UIButton *)sender{ 21 [self dismissViewControllerAnimated:NO completion:nil]; 22 } 23 //重写通知中心函数 24 -(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{ 25 NSString *strValue=change[@"new"]; 26 lblData.text=strValue; 27 } 28 - (void)didReceiveMemoryWarning { 29 [super didReceiveMemoryWarning]; 30 // Dispose of any resources that can be recreated. 31 }
TO BE FIRST,BEST OR DIFFERENT.