ios中的KVC和KVO

             最近研究了一下子KVC和KVO,KVC:即Key-Value-Coding 而KVO:即Key-Value-Observer

      KVC是针对NSObject的子类，因为它的实现是由于其括展类ＮSObject(NSKeyValueCoding),实现了

   - (void)setValue:(id)value forKey:(NSString *)key;   

    - (id)valueForKey:(NSString *)key;这两个方法的原因。

  还有一个说清楚点就是上面的两个方法不光针对属性，对于类中的对象型变量同样适用。

  而KVO也差不多，它是由于NSObject(NSKeyValueObserverRegistration)和NSObject(NSKeyValueObserving)的原因,用它可以实现回调功能下面是我写的，下面的例子我将其融合在一起

  

  

#import "BIDViewController.h"
#import "FirstViewController.h"
@interface BIDViewController ()
{
    FirstViewController* first;
    
}
@end

@implementation BIDViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.
    first=[[FirstViewController alloc] init];
    //观察FirstViewController中的变量name
    [first addObserver:self forKeyPath:@"name" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:NULL];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)clicked:(UIButton *)sender {
    [self presentViewController:first animated:YES completion:^{}];
}
//如果FirstViewController中的变量name的值变化执行下面
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if([keyPath isEqualToString:@"name"])
    {
        NSLog(@"observer name is %@",[first valueForKey:@"name"]);
    }
}

-(void)dealloc
{
    [self removeObserver:first forKeyPath:@"name"];
    [first release];
    [super dealloc];
}
@end

#import <UIKit/UIKit.h>

@interface FirstViewController : UIViewController
{
    NSString* name;
}
- (IBAction)clicked:(id)sender;
- (IBAction)otherClicked:(id)sender;

@end

#import "FirstViewController.h"

@interface FirstViewController ()
{
}
@end

@implementation FirstViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)clicked:(id)sender {
    //当为name设值时会执行BIDViewController中的观察方法，就可进行回调了，不过其范围是比不上真正意义上的回调
    [self setValue:@"chenliang" forKey:@"name"];

//    [self dismissModalViewControllerAnimated:YES];
    
    
}

- (IBAction)otherClicked:(id)sender {
    
    NSLog(@"firstVC name is %@",[self valueForKey:@"name"]);
}
@end

好了就说这么多有什么问题请多多指教