iOS KVC和KVO开发模式

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)valueforKey:(NSString *)key;

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

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，下面的例子将其融合在一起



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#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

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#import

@interface FirstViewController : UIViewController

{

NSString* name;

}

- (IBAction)clicked:(id)sender;

- (IBAction)otherClicked:(id)sender;

@end

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#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