iOS KVC与KVO的容易使用

iOS KVC与KVO的简单使用
#import "ViewController.h"
#import <Foundation/Foundation.h>
@interface DataModel : NSObject
@property (nonatomic,copy)NSString *stockName;
@property (nonatomic,assign)float price;
@end
@implementation DataModel
@end

@interface ViewController ()
@property UILabel *myLabel;
@property UIButton *myButton;
@property DataModel *model;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.model=[[DataModel alloc]init];
    [self.model setValue:@"searph" forKey:@"stockName"];
    [self.model setValue:@"10.0" forKey:@"price"];
    [self.model addObserver:self forKeyPath:@"price" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:nil];


    self.myLabel=[[UILabel alloc]initWithFrame:CGRectMake(130, 100, 100, 100)];
    self.myLabel.layer.masksToBounds=YES;
    self.myLabel.layer.cornerRadius=50;
    self.myLabel.textAlignment=NSTextAlignmentCenter;
    self.myLabel.textColor=[UIColor cyanColor];
    self.myLabel.backgroundColor=[UIColor grayColor];
    self.myLabel.text=[NSString stringWithFormat:@"%@",[self.model valueForKey:@"price"]];
    [self.view addSubview:self.myLabel];

    self.myButton=[UIButton buttonWithType:UIButtonTypeRoundedRect];
    self.myButton.frame=CGRectMake(130,200 , 100, 30);
    [self.myButton setTitle:@"按钮" forState:UIControlStateNormal];
    [self.myButton addTarget:self action:@selector(changeValue) forControlEvents:UIControlEventTouchUpInside];
    [self.myButton setBackgroundColor:[UIColor lightGrayColor]];
    [self.view addSubview:self.myButton];
}
- (void)changeValue{
    [self.model setValue:@"20.0" forKey:@"price"];
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
    if ([keyPath isEqualToString:@"price"]) {
        self.myLabel.text=[NSString stringWithFormat:@"%@",[self.model valueForKey:@"price"]];
    }
}
- (void)dealloc{
    [self.model removeObserver:self forKeyPath:@"price"];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}
@end

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