协议(protocol)

关于协议的一些定义,简单使用方法就不多说了.

协议可以添加哪些:

1.添加方法(类方法/属性方法)
2.添加属性

关于协议添加属性来举个例子:

#import <Foundation/Foundation.h>
@protocol PersonProtocol <NSObject>
@property (nonatomic, strong) NSString *name;//协议中的属性
@end

@interface Person : NSObject
@property (nonatomic, weak) id<PersonProtocol> delegade;
@end

找个类实现协议

#import "Student.h"

@interface Student ()<PersonProtocol>
@end

@implementation Student
//协议里的属性
@synthesize name;

@end

应用以下:

Person *onePerson = [Person new];
        Student *xiaoming = [Student new];
        onePerson.delegade = xiaoming;
        onePerson.delegade.name = @"xiaoming";
        NSLog(@"%@",xiaoming.name);

打印结果如下

xiaoming

通知(NSNotification)

先来看下常用的发通知的套路
发送:

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    NSLog(@"要发通知啦");
    [[NSNotificationCenter defaultCenter] postNotificationName:@"aaa" object:nil];
    NSLog(@"通知发完啦");
}

接收:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
 
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(testNoti) name:@"aaa" object:nil];
    return YES;
}

- (void)testNoti {
    NSLog(@"收到通知啦 %@",[NSThread currentThread]);
}

看下打印:

要发通知啦
 收到通知啦 <NSThread: 0x17406d880>{number = 1, name = main}
通知发完啦

总结:

通过postNotificationName:发送通知是同步的, 会卡住当前线程. 就是说, 发送通知后,会等到对方接收到通知并执行完收到通知的方法后才会接着往下走.

关于移除通知

iOS 9以后UIViewController 添加通知后可以不用移除, 系统会自动给移除.

异步发送通知

异步发送通知需要三步
1.创建通知(NSNotification)
2.创建通知队列(NSNotificationQueue)
3.将通知放入队列中执行

发送:

 NSLog(@"发送通知前");
//创建通知
    NSNotification *noti = [[NSNotification alloc] initWithName:@"aaa" object:nil userInfo:nil];
//将通知加入队列,并设置为NSPostASAP,当当前runloop完成之后立即post
    [[NSNotificationQueue defaultQueue] enqueueNotification:noti postingStyle:NSPostASAP];
    NSLog(@"发送通知后");

接收:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
 
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(testNoti) name:@"aaa" object:nil];
    return YES;
}

- (void)testNoti {
    NSLog(@"接收到通知了%@",[NSThread currentThread]);
}

打印:

 发送通知前
 发送通知后
 接收到通知了<NSThread: 0x282bb2e40>{number = 1, name = main}

将通知加入到队列的方法有个枚举参数:

typedef NS_ENUM(NSUInteger, NSPostingStyle) {
    NSPostWhenIdle = 1,      // 当runloop处于空闲状态时post
    NSPostASAP = 2,    // 当当前runloop完成之后立即post
    NSPostNow = 3    // 立即post，同步(会立即执行)
};

指定枚举参数后, 队列会根据type, 在合适的时机将NSNotification 发送到NSNotificationCenter,这就达到了异步执行的效果.

NSPostWhenIdle和NSPostASAP差不多, 都会异步执行,NSPostNow会立即执行

通知合并

将通知放入队列执行还有另外一个方法:
- (void)enqueueNotification:(NSNotification *)notification postingStyle:(NSPostingStyle)postingStyle coalesceMask:(NSNotificationCoalescing)coalesceMask forModes:(nullable NSArray<NSRunLoopMode> *)modes;
方法的第二个参数:(NSNotificationCoalescing)coalesceMask就是控制通知的合并策略.

如下:

typedef NS_OPTIONS(NSUInteger, NSNotificationCoalescing) {
    NSNotificationNoCoalescing = 0,  // 不合成
    NSNotificationCoalescingOnName = 1,  // 根据NSNotification的name字段进行合成
    NSNotificationCoalescingOnSender = 2  // 根据NSNotification的object字段进行合成
};

发送:

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    NSLog(@"发送通知前");
    NSNotification *noti = [[NSNotification alloc] initWithName:@"aaa" object:nil userInfo:nil];
    [[NSNotificationQueue defaultQueue] enqueueNotification:noti postingStyle:NSPostASAP];
    [[NSNotificationQueue defaultQueue] enqueueNotification:noti postingStyle:NSPostWhenIdle];
    [[NSNotificationQueue defaultQueue] enqueueNotification:noti postingStyle:NSPostWhenIdle coalesceMask:NSNotificationCoalescingOnName forModes:nil];
    NSLog(@"发送通知后");
}

接收:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
 
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(testNoti) name:@"aaa" object:nil];
    return YES;
}

- (void)testNoti {
    NSLog(@"接收到通知了%@",[NSThread currentThread]);
}

打印:

发送通知前
发送通知后
接收到通知了<NSThread: 0x280fbee40>{number = 1, name = main}

注意, 如果直接使用postNotificationName:或者指定NSPostNow提交方式或者指定合并策略为NSNotificationNoCoalescing 时,不会合并通知

参考:
http://www.cocoachina.com/ios/20170426/19124.html