開啟線程
- 分離主線程創(chuàng)建：
創(chuàng)建線程后會自動執(zhí)行，但是線程外部不可獲取到該線程對象
detachNewThreadWithBlock:
detachNewThreadSelector:toTarget:withObject:
+ (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;
[NSThread detachNewThreadSelector:(SEL)aSelector toTarget:(id)aTarget withObject:(id)anArgument];
[NSThread detachNewThreadWithBlock:^{
// do something
}];
-
構(gòu)造方法創(chuàng)建：
可拿到該線程對象，線程執(zhí)行需手動啟動- (instancetype)init NS_AVAILABLE(10_5, 2_0) NS_DESIGNATED_INITIALIZER; - (instancetype)initWithTarget:(id)target selector:(SEL)selector object:(nullable id)argument NS_AVAILABLE(10_5, 2_0); - (instancetype)initWithBlock:(void (^)(void))block API_AVAILABLE(macosx(10.12), ios(10.0), watchos(3.0), tvos(10.0)); NSThread *thread = [[NSThread alloc] initWithTarget:(id)aTarget selector:(SEL)aSelector object:(id)anArgument]; [thread start]; -
performSelector方法：NSObject的NSThreadPerformAdditions類別
任何OC對象均可由下列方法開啟子線程或回到主線程- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(nullable id)arg waitUntilDone:(BOOL)wait modes:(nullable NSArray<NSString *> *)array; - (void)performSelectorOnMainThread:(SEL)aSelector withObject:(nullable id)arg waitUntilDone:(BOOL)wait; // equivalent to the first method with kCFRunLoopCommonModes - (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(nullable id)arg waitUntilDone:(BOOL)wait modes:(nullable NSArray<NSString *> *)array NS_AVAILABLE(10_5, 2_0); - (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(nullable id)arg waitUntilDone:(BOOL)wait NS_AVAILABLE(10_5, 2_0); // equivalent to the first method with kCFRunLoopCommonModes - (void)performSelectorInBackground:(SEL)aSelector withObject:(nullable id)arg NS_AVAILABLE(10_5, 2_0);
NSThread生命周期
- 創(chuàng)建后開始執(zhí)行：start
- (void)start NS_AVAILABLE(10_5, 2_0);
- 執(zhí)行任務(wù):main
main方法為線程內(nèi)執(zhí)行的主要方法，NSThread的子類需重寫該方法，加入任務(wù)代碼
- (void)main NS_AVAILABLE(10_5, 2_0);
- 取消：cancel
- (void)cancel NS_AVAILABLE(10_5, 2_0);
- 終止線程：exit
exit是類方法，表示終止當(dāng)前線程，且不可恢復(fù)
+ (void)exit;
- 一些屬性
- isExecuting：是否正在執(zhí)行
@property (readonly, getter=isExecuting) BOOL executing NS_AVAILABLE(10_5, 2_0); - isFinished：是否結(jié)束
@property (readonly, getter=isFinished) BOOL finished NS_AVAILABLE(10_5, 2_0); - isCancelled：是否取消
@property (readonly, getter=isCancelled) BOOL cancelled NS_AVAILABLE(10_5, 2_0);
- isExecuting：是否正在執(zhí)行
線程間通訊：通過NSObject的NSThreadPerformAdditions類別方法調(diào)用
- 回歸主線程
在主線程中運行方法，wait表示是否阻塞這個方法的調(diào)用，如果為YES則等待主線程中運行方法結(jié)束。一般可用于在子線程中調(diào)用UI方法。
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(nullable id)arg waitUntilDone:(BOOL)wait modes:(nullable NSArray<NSString *> *)array;
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(nullable id)arg waitUntilDone:(BOOL)wait;
- 在指定線程中執(zhí)行
在指定線程中執(zhí)行，但該線程必須具備runloop（kCFRunLoopCommonModes）
// equivalent to the first method with kCFRunLoopCommonModes
- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(nullable id)arg waitUntilDone:(BOOL)wait modes:(nullable NSArray<NSString *> *)array NS_AVAILABLE(10_5, 2_0);
- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(nullable id)arg waitUntilDone:(BOOL)wait NS_AVAILABLE(10_5, 2_0);
- Background
// equivalent to the first method with kCFRunLoopCommonModes
- (void)performSelectorInBackground:(SEL)aSelector withObject:(nullable id)arg NS_AVAILABLE(10_5, 2_0);
NSThread的其它一些常用的屬性和方法
- 獲得當(dāng)前線程
@property (class, readonly, strong) NSThread *currentThread;
- 線程休眠
+ (void)sleepUntilDate:(NSDate *)date;
+ (void)sleepForTimeInterval:(NSTimeInterval)ti;
- 獲得主線程
@property (class, readonly, strong) NSThread *mainThread NS_AVAILABLE(10_5, 2_0);
- 當(dāng)前線程是否主線程
@property (readonly) BOOL isMainThread NS_AVAILABLE(10_5, 2_0);
@property (class, readonly) BOOL isMainThread NS_AVAILABLE(10_5, 2_0);
- 線程名
@property (nullable, copy) NSString *name NS_AVAILABLE(10_5, 2_0);
- 線程優(yōu)先級
+ (double)threadPriority;
+ (BOOL)setThreadPriority:(double)p;
@property double threadPriority NS_AVAILABLE(10_6, 4_0); // To be deprecated; use qualityOfService below
- 服務(wù)質(zhì)量：NSQualityOfService
從iOS8開始，蘋果框架概念基礎(chǔ)中將不再過分強調(diào)線程這個概念。新的qualityOfService屬性替換了ThreadPriority。這些新的語義允許應(yīng)用程序推遲非關(guān)鍵工作，以確保始終如一的用戶體驗。
@property NSQualityOfService qualityOfService NS_AVAILABLE(10_10, 8_0); // read-only after the thread is started
typedef NS_ENUM(NSInteger, NSQualityOfService) {
// 與用戶交互的任務(wù)，這些任務(wù)通常跟UI級別的刷新相關(guān)，比如動畫，這些任務(wù)需要在一瞬間完成
NSQualityOfServiceUserInteractive = 0x21,
// 在實現(xiàn)用戶精確請求請求相關(guān)工作時使用UserInitiated QoS，但不要求精確到毫秒，比如動畫。例如，如果用戶打開email app馬上查看郵件。
NSQualityOfServiceUserInitiated = 0x19,
// Utility QoS用于執(zhí)行已經(jīng)由用戶請求自動發(fā)生的任務(wù)。例如，電子郵件應(yīng)用程序可以被配置為每隔5分鐘自動檢查郵件。如果系統(tǒng)是非常有限的資源，而電子郵件檢查被推遲幾分鐘這也是被允許的。
NSQualityOfServiceUtility = 0x11,
// Background QoS用于執(zhí)行用戶可能甚至都沒有意識到正在發(fā)生的工作，比如email app可能使用它來執(zhí)行索引搜索
NSQualityOfServiceBackground = 0x09,
// 優(yōu)先級介于user-initiated 和 utility，當(dāng)沒有 QoS信息時默認(rèn)使用，開發(fā)者不應(yīng)該使用這個值來設(shè)置自己的任務(wù)
NSQualityOfServiceDefault = -1
} NS_ENUM_AVAILABLE(10_10, 8_0);
- 線程數(shù)據(jù)：threadDictionary
@property (readonly, retain) NSMutableDictionary *threadDictionary;
- 指定線程的?？臻g：stackSize屬性，值是4KB及其倍數(shù)，最大512KB，主線程最大1MB
@property NSUInteger stackSize NS_AVAILABLE(10_5, 2_0);
一些非線程調(diào)用（NSObject的NSThreadPerformAdditions類別方法）
- 在當(dāng)前線程立即執(zhí)行：注意它們會阻塞當(dāng)前線程（包括UI線程）：
- (id)performSelector:(SEL)aSelector;
- (id)performSelector:(SEL)aSelector withObject:(id)object;
- (id)performSelector:(SEL)aSelector withObject:(id)object1 withObject:(id)object2;
- 在當(dāng)前線程延遲執(zhí)行：
- (void)performSelector:(SEL)aSelector withObject:(id)anArgument afterDelay:(NSTimeInterval)delay inModes:(NSArray *)modes;
- (void)performSelector:(SEL)aSelector withObject:(id)anArgument afterDelay:(NSTimeInterval)delay;
如果當(dāng)前線程沒有顯式使用NSRunLoop或已退出就無法執(zhí)行了，需要注意，它們可以被下列方法終止：
+ (void)cancelPreviousPerformRequestsWithTarget:(id)aTarget selector:(SEL)aSelector object:(id)anArgument;
+ (void)cancelPreviousPerformRequestsWithTarget:(id)aTarget;
