KVC 和KVO浅谈

  1 A.设置将要监视的对象：
  2 
  3 //  StockData.h
  4 
  5 #import <Foundation/Foundation.h>
  6 
  7 @interface StockData : NSObject
  8 {
  9     NSString *stockName;
 10    NSString  *price;
 11 
 12 }
 13 @end
 14 //  StockData.m
 15 #import "StockData.h"
 16 
 17 @implementation StockData
 18 
 19 @end
 20 
 21 
 22 B、编辑主界面
 23 //  MainViewController.h
 24 #import <UIKit/UIKit.h>
 25 
 26 @interface MainViewController : UIViewController
 27 
 28 @end
 29 
 30 //  MainViewController.m
 31 
 32 #import "MainViewController.h"
 33 #import "StockData.h"
 34 
 35 
 36 @interface MainViewController ()
 37 
 38 @property(nonatomic,retain)StockData *stockForKVO;
 39 
 40 @property(nonatomic,retain)UILabel *aLabel;
 41 
 42 @property(nonatomic,assign)NSInteger number;
 43 
 44 @end
 45 
 46 @implementation MainViewController
 47 
 48 - (void)viewDidLoad {
 49     [super viewDidLoad];
 50     // Do any additional setup after loading the view.
 51    
 52     self.number = 0;
 53    
 54     _stockForKVO = [[StockData alloc]init];
 55    
 56     [_stockForKVO setValue:@"searph" forKey:@"stockName"];
 57 
 58     [_stockForKVO setValue:[NSString stringWithFormat:@"%ld",_number] forKey:@"price"];
 59    
 60     [_stockForKVO addObserver:self forKeyPath:@"price" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:NULL];
 61    
 62     self.aLabel = [[UILabel alloc]initWithFrame:CGRectMake(100, 200, 100, 30)];
 63    
 64     self.aLabel.textAlignment = NSTextAlignmentCenter;
 65     self.aLabel.textColor = [UIColor orangeColor];
 66     self.aLabel.text  = [_stockForKVO valueForKey:@"price"];
 67     [self.view addSubview:self.aLabel];
 68 //    [self.aLabel release];
 69    
 70     UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
 71    
 72     btn.backgroundColor = [UIColor whiteColor];
 73     btn.frame = CGRectMake(100, 30, 100, 30);
 74    
 75     [btn addTarget:self action:@selector(handleDown:) forControlEvents:UIControlEventTouchUpInside];
 76    
 77     [self.view addSubview:btn];
 78    
 79 }
 80 
 81 - (void)handleDown:(UIButton *)sender{
 82 
 83    
 84  
 85  
 86  
 87     _number ++;
 88    
 89     [_stockForKVO setValue:[NSString stringWithFormat:@"%ld",_number] forKey:@"price"];
 90 
 91 }
 92 
 93 
 94 - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
 95 
 96     if ([keyPath isEqualToString:@"price"]) {
 97        
 98         self.aLabel.text = [_stockForKVO valueForKey:@"price"];
 99        
100        
101     }
102    
103    
104 
105 
106 }
107 
108 
109 - (void)dealloc{
110     [super dealloc];
111     [_stockForKVO removeObserver:self forKeyPath:@"price"];
112     [_stockForKVO release];
113 
114 
115 }
116 
117 
118 - (void)didReceiveMemoryWarning {
119     [super didReceiveMemoryWarning];
120     // Dispose of any resources that can be recreated.
121 }
122 
123 /*
124 #pragma mark - Navigation
125 
126 // In a storyboard-based application, you will often want to do a little preparation before navigation
127 - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
128     // Get the new view controller using [segue destinationViewController].
129     // Pass the selected object to the new view controller.
130 }
131 */
132 
133 @end