[消息传递之七]－KVO练习

超、凢脫俗 2022-08-19 11:09 170阅读 0赞

#import <UIKit/UIKit.h>
    
    @interface ViewController : UIViewController
    
    @property (strong, nonatomic) IBOutlet UIButton *btnKVO;
    @property (strong, nonatomic) IBOutlet UIButton *btnDelete;
    @property (strong, nonatomic) IBOutlet UIButton *btnResume;
    
    - (IBAction)ResumeClick:(UIButton *)sender;
    - (IBAction)KVOClick:(UIButton *)sender;
    - (IBAction)DeleteClick:(UIButton *)sender;
    @end

#import "ViewController.h"
    #import "TestKVO.h"
    
    @interface ViewController ()
    
    @end
    
    @implementation ViewController
    {
        TestKVO* t;
        NSInteger money;
    }
    
    - (void)viewDidLoad {
        [super viewDidLoad];
        t =[[TestKVO alloc] init];
        money = 20;
        self.btnDelete.enabled = NO;
        self.btnKVO.enabled = false;
        // Do any additional setup after loading the view, typically from a nib.
    }
    
    -(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
    {
        if ([keyPath compare:@"HaveMoney" ] == NSOrderedSame) {
            NSString* str = (__bridge NSString*)context;
            NSLog(@"Money is %ld,Context is %@",[object HaveMoney],str);
            if (change) {
                [change enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
                    NSLog(@"key is %@, obj is %@",key,obj);
                }];
            }
        }
        else
        {
            [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
        }
    }
    - (void)didReceiveMemoryWarning {
        [super didReceiveMemoryWarning];
        // Dispose of any resources that can be recreated.
    }
    
    - (IBAction)KVOClick:(UIButton *)sender {
        t.HaveMoney = money;
        money++;
    }
    
    - (IBAction)DeleteClick:(UIButton *)sender {
        [t removeObserver:self forKeyPath:@"HaveMoney"];
        self.btnResume.enabled = YES;
        self.btnDelete.enabled = NO;
        self.btnKVO.enabled = NO;
    }
    
    - (IBAction)ResumeClick:(UIButton *)sender {
        [t addObserver:self forKeyPath:@"HaveMoney" options:NSKeyValueObservingOptionNew context:@"hello"];
        self.btnKVO.enabled = YES;
        self.btnDelete.enabled = YES;
        self.btnResume.enabled = NO;
    }
    @end

1，可以重复添加，添加后也是重复执行，这点要注意。

2，删除一次后，就不能重复删除了，不清楚如何检测自己的observer。

3，要响应父类的，删除的时候，可以利用context的值，看看是否本类注册的。