NSNotification 通知

在IOS中，每一个运行中的程序都有个NSNotificationCenter(通知中心)成员变量。如果有对象需要关注某一个NSNotification（通知），

首先去通知中心注册

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(todoOne) name:@"Method" object:nil];

其中self就是关注某一通知的对象，也叫Observer；@"Method"指的是Notification的名字；@selector里面的方法todoOne就是这个对象接受到通知(Method)的时候该执行的动作；最后一个参数指的是发送通知的对象，如果发送通知的对象为nil，则通知中心将所有名字为@“Method”的NSNotification转发给关注这个通知的对象self。

其次，在需要的时候通知中心发送通知，这个时候，关注Method的对象就会调用todoOne方法。

[[NSNotificationCenter defaultCenter] postNotificationName:@"Method" object:self];

最后移除关注Method的对象

[[NSNotificationCenter defaultCenter] removeObserver:self];

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(todoOne) name:@"Method" object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(todoTwo:) name:@"two" object:nil];
    
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

- (void)todoOne{
    NSLog(@"todoOne is called");
}

- (void)todoTwo:(NSNotification *)object{
    NSLog(@"todoTwo: is called %@",object);
    NSNumber *integer = [[object userInfo] objectForKey:@"sum"];
    NSLog(@"the received is %d",[integer intValue]);
    
}

- (IBAction)sendNotification1:(id)sender {
    [[NSNotificationCenter defaultCenter] postNotificationName:@"Method" object:self];
}

- (IBAction)sendNotification2:(id)sender {
    NSDictionary *mDictionary = [NSDictionary dictionaryWithObject:[NSNumber numberWithInteger:5] forKey:@"sum"];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"two" object:self userInfo:mDictionary];
}
- (IBAction)removeNotification:(id)sender {
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    NSLog(@"remove Notification");
}
@end

NSNotification类

提供给observer的信息包裹. notification对象有两个重要的成员变量: name 和 object.

- (NSString *)name;

- (id)object;

- (NSDictionary *)userInfo;我们想要notification对象传递更多的信息

+ (id)notificationWithName:(NSString *)aName object:(id)anObject;

+ (id)notificationWithName:(NSString *)aName object:(id)anObject userInfo:(NSDictionary *)aUserInfo;

NSNotificationCenter类

+ (id)defaultCenter;返回notification center [类方法,返回全局对象, 单件模式.cocoa的很多的全局对象都是通过类似方法实现]

    

- (void)addObserver:(id)observer selector:(SEL)aSelector name:(NSString *)aName object:(id)anObject;

 如果notificationName为nil. 那么notification center将anObject发送的所有notification转发给observer

. 如果anObject为nil.那么notification center将所有名字为notificationName的notification转发给observer

- (void)postNotification:(NSNotification *)notification;

- (void)postNotificationName:(NSString *)aName object:(id)anObject;

- (void)postNotificationName:(NSString *)aName object:(id)anObject userInfo:(NSDictionary *)aUserInfo;

- (void)removeObserver:(id)observer;

- (void)removeObserver:(id)observer name:(NSString *)aName object:(id)anObject;

参考博客：

http://blog.sina.com.cn/s/blog_5df7dcaf0100c0q2.html

http://blog.csdn.net/ch_soft/article/details/6682809