iOS开发线程之NSThread

1、初始化

- (instancetype)init API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0)) NS_DESIGNATED_INITIALIZER;
- (instancetype)initWithTarget:(id)target selector:(SEL)selector object:(nullable id)argument API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));
- (instancetype)initWithBlock:(void (^)(void))block API_AVAILABLE(macosx(10.12), ios(10.0), watchos(3.0), tvos(10.0));

2、开启线程

+ (void)detachNewThreadWithBlock:(void (^)(void))block API_AVAILABLE(macosx(10.12), ios(10.0), watchos(3.0), tvos(10.0));
+ (void)detachNewThreadSelector:(SEL)selector toTarget:(id)target withObject:(nullable id)argument;
- (void)start API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));
- (void)main API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));    // thread body method

　　特点：main

//执行start方法后会自动调用main方法。
//main是默认的初始化和调用selector的方法。如果要继承NSThread，可以重写main方法来执行新线程的主要部分。重写的mian方法不需要调用super。不要直接调用mian方法，而是通过start方法来调用。

3、停止线程

+ (void)sleepUntilDate:(NSDate *)date;//休眠到指定时间
+ (void)sleepForTimeInterval:(NSTimeInterval)ti;//休眠多久
+ (void)exit;//退出所有线程
- (void)cancel API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));//取消线程

　　特点：exit

//exit方法先执行currentThread类方法来获取当前线程。
//由于退出线程前给默认通知中心发送NSThreadWillExitNotification通知，并把当前线程作为参数，因为post通知是同时发送的，所以所有NSThreadWillExitNotification 通知的观察者都会收到通知，导致所有线程都退出。

4、描述线程状态

@property (readonly, getter=isExecuting) BOOL executing;//是否在执行
@property (readonly, getter=isFinished) BOOL finished ;//是否执行完毕
@property (readonly, getter=isCancelled) BOOL cancelled;//是否已经取消，此时finished可能为NO

5、主线程和多线程

@property (readonly) BOOL isMainThread ;//是否是主线程
@property (class, readonly, strong) NSThread *mainThread ;//获取当前主线程

+ (BOOL)isMultiThreaded;//是否是多线程
@property (class, readonly, strong) NSThread *currentThread;//当前线程 1为主线程
@property (class, readonly, copy) NSArray<NSNumber *> *callStackReturnAddresses;//线程函数地址
@property (class, readonly, copy) NSArray<NSString *> *callStackSymbols;//当前线程的调用栈

6、属性设置

//可以使用返回的字典来保存线程的特定数据。这只是一个普通的字典，用来保存所有开发者感兴趣的数据。
@property (readonly, retain) NSMutableDictionary *threadDictionary;
//线程的堆内存大小字节数。必须是4KB的倍数。要使设置有用，必须在start方法调用前设置。
@property NSUInteger stackSize;
@property (nullable, copy) NSString *name;//线程名字

7、优先级

+ (double)threadPriority;//当前线程优先级【0.0--1.0】默认0.5
+ (BOOL)setThreadPriority:(double)p;//设置优先级成功返回YES

@property double threadPriority API_AVAILABLE(macos(10.6), ios(4.0), watchos(2.0), tvos(9.0)); // To be deprecated; use qualityOfService below
@property NSQualityOfService qualityOfService API_AVAILABLE(macos(10.10), ios(8.0), watchos(2.0), tvos(9.0)); // read-only after the thread is started

typedef NS_ENUM(NSInteger, NSQualityOfService) {
    /* 最高优先级，主要用于提供交互UI的操作，比如处理点击事件，绘制图像到屏幕上 */
    NSQualityOfServiceUserInteractive = 0x21,
    /* 次高优先级，主要用于执行需要立即返回的任务 */
    NSQualityOfServiceUserInitiated = 0x19,
    /* 普通优先级，主要用于不需要立即返回的任务*/
    NSQualityOfServiceUtility = 0x11,
    /* 后台优先级，用于完全不紧急的任务*/
    NSQualityOfServiceBackground = 0x09,
    /* 默认优先级，当没有设置优先级的时候，线程默认优先级*/
    NSQualityOfServiceDefault = -1
} API_AVAILABLE(macos(10.10), ios(8.0), watchos(2.0), tvos(9.0));

8、通知

FOUNDATION_EXPORT NSNotificationName const NSWillBecomeMultiThreadedNotification;//由当前线程派生出第一个其他线程时发送，一般一个线程只发送一次
FOUNDATION_EXPORT NSNotificationName const NSDidBecomeSingleThreadedNotification;//未知。
FOUNDATION_EXPORT NSNotificationName const NSThreadWillExitNotification;//当线程对象获取到exit消息时，广播这个通知。

9、NSThreadPerformAdditions类别

@interface NSObject (NSThreadPerformAdditions)

- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(nullable id)arg waitUntilDone:(BOOL)wait modes:(nullable NSArray<NSString *> *)array;//用于线程通信,子线程传到主线程
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(nullable id)arg waitUntilDone:(BOOL)wait;// 用于线程通信,子线程传到主线程,默认的运行时模式: kCFRunLoopCommonModes
- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(nullable id)arg waitUntilDone:(BOOL)wait modes:(nullable NSArray<NSString *> *)array API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));//用于线程之间的通信
- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(nullable id)arg waitUntilDone:(BOOL)wait API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));//用于线程之间的通信
- (void)performSelectorInBackground:(SEL)aSelector withObject:(nullable id)arg API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));// 隐式创建线程,默认的运行时模式 kCFRunLoopCommonModes

@end