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在iOS開發(fā)中，經(jīng)常會(huì)用到多線程開發(fā)的情況，這時(shí)候如果多個(gè)線程同時(shí)訪問(wèn)同一塊資源時(shí)，就很容易引發(fā)數(shù)據(jù)錯(cuò)亂和數(shù)據(jù)安全的問(wèn)題，這個(gè)時(shí)候我們就需要有一個(gè)方法來(lái)保證每次只有一個(gè)線程訪問(wèn)這一塊資源，這個(gè)方法就是鎖。

iOS中一共有8中常用的鎖，我們用YY大神的一張圖來(lái)看一下這些鎖的性能。

lcok.png

OSSpinLock 自旋鎖

OSSpinLock 自旋鎖在圖表中可以看到，性能是最高的，大概在150us，但是YY大神在不再安全的 OSSpinLock中說(shuō)道OSSpinLock自旋鎖已經(jīng)不再安全了。

而且也可以看到OSSpinLock已經(jīng)在iOS 10.0之后廢棄了。

lock_OSSpinLock.png

好了，接下來(lái)看一下OSSpinLock中的方法。

OS_SPINLOCK_INIT：默認(rèn)值為 0,在 locked 狀態(tài)時(shí)就會(huì)大于 0，unlocked狀態(tài)下為 0
OSSpinLockLock(&oslock)：上鎖，參數(shù)為 OSSpinLock 地址
OSSpinLockUnlock(&oslock)：解鎖，參數(shù)為 OSSpinLock 地址
OSSpinLockTry(&oslock)：嘗試加鎖，可以加鎖則立即加鎖并返回 YES,反之返回 NO

接下來(lái)我們測(cè)試一下，比如下面一段代碼中，我們開啟兩個(gè)異步線程。


- (void)setOSSpinLock

{

 __block OSSpinLock ossPinLock = OS_SPINLOCK_INIT;

 __block NSInteger number = 10;

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 number += 10;

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 });

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 number += 20;

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 });

}

可以看到打印出來(lái)的數(shù)據(jù)都是錯(cuò)亂的：


2018-04-23 16:33:12.655341+0800 LockDemo[88725:6234113] 當(dāng)前線程：<NSThread: 0x604000270d00>{number = 3, name = (null)}，number=10

2018-04-23 16:33:12.655341+0800 LockDemo[88725:6234116] 當(dāng)前線程：<NSThread: 0x60000026f340>{number = 4, name = (null)}，number=10

2018-04-23 16:33:12.655651+0800 LockDemo[88725:6234116] 當(dāng)前線程：<NSThread: 0x60000026f340>{number = 4, name = (null)}，number=40

2018-04-23 16:33:12.655655+0800 LockDemo[88725:6234113] 當(dāng)前線程：<NSThread: 0x604000270d00>{number = 3, name = (null)}，number=40

這時(shí)候，我們添加一下上OSSpinLock自旋鎖:

首先引入OSSpinLock自旋鎖的庫(kù):


#import <libkern/OSAtomic.h>


- (void)setOSSpinLock

{

 __block OSSpinLock ossPinLock = OS_SPINLOCK_INIT;

 __block NSInteger number = 10;

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，OSSpinLock上鎖",[NSThread currentThread]);

 OSSpinLockLock(&ossPinLock);

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 number += 10;

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 NSLog(@"當(dāng)前線程：%@，OSSpinLock解鎖",[NSThread currentThread]);

 OSSpinLockUnlock(&ossPinLock);

 });

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，OSSpinLock上鎖",[NSThread currentThread]);

 OSSpinLockLock(&ossPinLock);

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 number += 20;

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 NSLog(@"當(dāng)前線程：%@，OSSpinLock解鎖",[NSThread currentThread]);

 OSSpinLockUnlock(&ossPinLock);

 });

}

可以看到打印的數(shù)據(jù)：


2018-04-23 16:34:40.764216+0800 LockDemo[88797:6236783] 當(dāng)前線程：<NSThread: 0x60000027dcc0>{number = 3, name = (null)}，OSSpinLock上鎖

2018-04-23 16:34:40.764216+0800 LockDemo[88797:6236781] 當(dāng)前線程：<NSThread: 0x60000027da40>{number = 4, name = (null)}，OSSpinLock上鎖

2018-04-23 16:34:40.764450+0800 LockDemo[88797:6236783] 當(dāng)前線程：<NSThread: 0x60000027dcc0>{number = 3, name = (null)}，number=10

2018-04-23 16:34:40.764577+0800 LockDemo[88797:6236783] 當(dāng)前線程：<NSThread: 0x60000027dcc0>{number = 3, name = (null)}，number=20

2018-04-23 16:34:40.764736+0800 LockDemo[88797:6236783] 當(dāng)前線程：<NSThread: 0x60000027dcc0>{number = 3, name = (null)}，OSSpinLock解鎖

2018-04-23 16:34:40.766647+0800 LockDemo[88797:6236781] 當(dāng)前線程：<NSThread: 0x60000027da40>{number = 4, name = (null)}，number=20

2018-04-23 16:34:40.766910+0800 LockDemo[88797:6236781] 當(dāng)前線程：<NSThread: 0x60000027da40>{number = 4, name = (null)}，number=40

2018-04-23 16:34:40.768117+0800 LockDemo[88797:6236781] 當(dāng)前線程：<NSThread: 0x60000027da40>{number = 4, name = (null)}，OSSpinLock解鎖

dispatch_semaphore 信號(hào)量

信號(hào)量是僅次于自旋鎖的方法，使用的是GCD提供的API：

dispatch_semaphore_create 創(chuàng)建一個(gè)Semphore并初始化信號(hào)的總量。
dispatch_semaphore_signal 發(fā)送一個(gè)信號(hào)，讓信號(hào)總量加1。
dispatch_semaphore_wait 可以使總信號(hào)量減1，讓信號(hào)總量為0時(shí)就會(huì)一直等待，否則就可以正常執(zhí)行。

這次我們就不上測(cè)試的代碼了，直接放上增加信號(hào)量的代碼：


- (void)setSemaphore

{

 dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);

 dispatch_time_t overTime = dispatch_time(DISPATCH_TIME_NOW, 3.0f * NSEC_PER_SEC);

 __block NSInteger number = 10;

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，semaphore信號(hào)量+1",[NSThread currentThread]);

 dispatch_semaphore_signal(semaphore);

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 number += 10;

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 NSLog(@"當(dāng)前線程：%@，semaphore信號(hào)量-1",[NSThread currentThread]);

 dispatch_semaphore_wait(semaphore, overTime);

 });

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，semaphore信號(hào)量+1",[NSThread currentThread]);

 dispatch_semaphore_signal(semaphore);

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 number += 20;

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 NSLog(@"當(dāng)前線程：%@，semaphore信號(hào)量-1",[NSThread currentThread]);

 dispatch_semaphore_wait(semaphore, overTime);

 });

}

打印結(jié)果：


2018-04-23 17:05:22.368340+0800 LockDemo[89577:6266694] 當(dāng)前線程：<NSThread: 0x60000026ed00>{number = 3, name = (null)}，semaphore信號(hào)量+1

2018-04-23 17:05:22.368340+0800 LockDemo[89577:6266693] 當(dāng)前線程：<NSThread: 0x60000026ed80>{number = 4, name = (null)}，semaphore信號(hào)量+1

2018-04-23 17:05:22.368625+0800 LockDemo[89577:6266694] 當(dāng)前線程：<NSThread: 0x60000026ed00>{number = 3, name = (null)}，number=10

2018-04-23 17:05:22.368630+0800 LockDemo[89577:6266693] 當(dāng)前線程：<NSThread: 0x60000026ed80>{number = 4, name = (null)}，number=10

2018-04-23 17:05:22.368763+0800 LockDemo[89577:6266694] 當(dāng)前線程：<NSThread: 0x60000026ed00>{number = 3, name = (null)}，number=20

2018-04-23 17:05:22.368888+0800 LockDemo[89577:6266694] 當(dāng)前線程：<NSThread: 0x60000026ed00>{number = 3, name = (null)}，semaphore信號(hào)量-1

2018-04-23 17:05:22.368887+0800 LockDemo[89577:6266693] 當(dāng)前線程：<NSThread: 0x60000026ed80>{number = 4, name = (null)}，number=40

2018-04-23 17:05:22.369799+0800 LockDemo[89577:6266693] 當(dāng)前線程：<NSThread: 0x60000026ed80>{number = 4, name = (null)}，semaphore信號(hào)量-1

pthread_mutex 互斥鎖

YY大神在之前的文章中已經(jīng)說(shuō)過(guò)OSSpinLock已經(jīng)不再是線程安全的并把自己開源項(xiàng)目中的OSSpinLock都換成了pthread_mutex。

接下來(lái)我們看一下互斥鎖提供的方法：

pthread_mutex_init(&pLock, NULL);：參數(shù)為 pthread_mutex 地址，第二個(gè)參數(shù)默認(rèn)PTHREAD_MUTEX_NORMAL
pthread_mutex_lock(&pLock)：上鎖，參數(shù)為 pthread_mutex 地址
pthread_mutex_unlock(&pLock)：解鎖，參數(shù)為 pthread_mutex 地址
pthread_mutex_trylock(&pLock)：嘗試加鎖，可以加鎖則立即加鎖并返回 0 ,否者返回一個(gè)錯(cuò)誤提示碼。

接下來(lái)看代碼：


- (void)setPthread_mutex

{

 static pthread_mutex_t pLock;

 pthread_mutex_init(&pLock, NULL);

 __block NSInteger number = 10;

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，上鎖",[NSThread currentThread]);

 pthread_mutex_lock(&pLock);

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 number += 10;

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 NSLog(@"當(dāng)前線程：%@，解鎖",[NSThread currentThread]);

 pthread_mutex_unlock(&pLock);

 });

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，上鎖",[NSThread currentThread]);

 pthread_mutex_lock(&pLock);

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 number += 20;

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 NSLog(@"當(dāng)前線程：%@，解鎖",[NSThread currentThread]);

 pthread_mutex_unlock(&pLock);

 });

}

然后是打印結(jié)果：


2018-04-23 17:13:09.376128+0800 LockDemo[89821:6278824] 當(dāng)前線程：<NSThread: 0x600000474900>{number = 3, name = (null)}，上鎖

2018-04-23 17:13:09.376128+0800 LockDemo[89821:6278825] 當(dāng)前線程：<NSThread: 0x6000004744c0>{number = 4, name = (null)}，上鎖

2018-04-23 17:13:09.376419+0800 LockDemo[89821:6278824] 當(dāng)前線程：<NSThread: 0x600000474900>{number = 3, name = (null)}，number=10

2018-04-23 17:13:09.376547+0800 LockDemo[89821:6278824] 當(dāng)前線程：<NSThread: 0x600000474900>{number = 3, name = (null)}，number=20

2018-04-23 17:13:09.376759+0800 LockDemo[89821:6278824] 當(dāng)前線程：<NSThread: 0x600000474900>{number = 3, name = (null)}，解鎖

2018-04-23 17:13:09.378000+0800 LockDemo[89821:6278825] 當(dāng)前線程：<NSThread: 0x6000004744c0>{number = 4, name = (null)}，number=20

2018-04-23 17:13:09.378627+0800 LockDemo[89821:6278825] 當(dāng)前線程：<NSThread: 0x6000004744c0>{number = 4, name = (null)}，number=40

2018-04-23 17:13:09.378846+0800 LockDemo[89821:6278825] 當(dāng)前線程：<NSThread: 0x6000004744c0>{number = 4, name = (null)}，解鎖

pthread_mutex(recursive) 遞歸鎖

遞歸鎖最大的特點(diǎn)就是允許同一個(gè)線程在未釋放其擁有的鎖時(shí)反復(fù)對(duì)該鎖進(jìn)行加鎖操作。而之前介紹的幾種鎖可以看到，加鎖后只能有一個(gè)線程訪問(wèn)該對(duì)象，后面的線程需要排隊(duì)，并且lock和unlock都是對(duì)應(yīng)出現(xiàn)的。

下面是代碼：


- (void)setPthreadMutexRecursive

{

 static pthread_mutex_t pLock;

 pthread_mutexattr_t attr;

 //初始化attr并且給它賦予默認(rèn)

 pthread_mutexattr_init(&attr);

 //設(shè)置鎖類型，這邊是設(shè)置為遞歸鎖

 pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);

 pthread_mutex_init(&pLock, &attr);

 //銷毀一個(gè)屬性對(duì)象，在重新進(jìn)行初始化之前該結(jié)構(gòu)不能重新使用

 pthread_mutexattr_destroy(&attr);

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 static void (^RecursiveBlock)(int);

 RecursiveBlock = ^(int value) {

 pthread_mutex_lock(&pLock);

 if (value > 0) {

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],value);

 RecursiveBlock(value - 1);

 }

 pthread_mutex_unlock(&pLock);

 };

 RecursiveBlock(5);

 });

}

打印結(jié)果：


2018-04-23 17:34:36.252635+0800 LockDemo[90381:6304880] 當(dāng)前線程：<NSThread: 0x60000046ec00>{number = 3, name = (null)}，number=5

2018-04-23 17:34:36.252947+0800 LockDemo[90381:6304880] 當(dāng)前線程：<NSThread: 0x60000046ec00>{number = 3, name = (null)}，number=4

2018-04-23 17:34:36.253129+0800 LockDemo[90381:6304880] 當(dāng)前線程：<NSThread: 0x60000046ec00>{number = 3, name = (null)}，number=3

2018-04-23 17:34:36.254451+0800 LockDemo[90381:6304880] 當(dāng)前線程：<NSThread: 0x60000046ec00>{number = 3, name = (null)}，number=2

2018-04-23 17:34:36.254692+0800 LockDemo[90381:6304880] 當(dāng)前線程：<NSThread: 0x60000046ec00>{number = 3, name = (null)}，number=1

NSLock

NSLock看名字就會(huì)熟悉一些了，我們來(lái)看一下他的API：

lock：上鎖
unlock：解鎖
trylock：能加鎖返回 YES 并執(zhí)行加鎖操作，相當(dāng)于 lock，反之返回 NO。
lockBeforeDate：這個(gè)方法表示會(huì)在傳入的時(shí)間內(nèi)嘗試加鎖，若能加鎖則執(zhí)行加鎖操作并返回 YES，反之返回 NO。

接下來(lái)上代碼：


- (void)setNSLock

{

 NSLock *lock = [NSLock new];

 __block NSInteger number = 10;

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，NSLock上鎖",[NSThread currentThread]);

 [lock lock];

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 number += 10;

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 NSLog(@"當(dāng)前線程：%@，NSLock解鎖",[NSThread currentThread]);

 [lock unlock];

 });

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，NSLock上鎖",[NSThread currentThread]);

 [lock lock];

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 number += 20;

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 NSLog(@"當(dāng)前線程：%@，NSLock解鎖",[NSThread currentThread]);

 [lock unlock];

 });

}

打印結(jié)果：


2018-04-23 17:41:40.355403+0800 LockDemo[90636:6315709] 當(dāng)前線程：<NSThread: 0x604000464340>{number = 4, name = (null)}，NSLock上鎖

2018-04-23 17:41:40.355403+0800 LockDemo[90636:6315707] 當(dāng)前線程：<NSThread: 0x604000464400>{number = 3, name = (null)}，NSLock上鎖

2018-04-23 17:41:40.355620+0800 LockDemo[90636:6315709] 當(dāng)前線程：<NSThread: 0x604000464340>{number = 4, name = (null)}，number=10

2018-04-23 17:41:40.355768+0800 LockDemo[90636:6315709] 當(dāng)前線程：<NSThread: 0x604000464340>{number = 4, name = (null)}，number=30

2018-04-23 17:41:40.355913+0800 LockDemo[90636:6315709] 當(dāng)前線程：<NSThread: 0x604000464340>{number = 4, name = (null)}，NSLock解鎖

2018-04-23 17:41:40.357151+0800 LockDemo[90636:6315707] 當(dāng)前線程：<NSThread: 0x604000464400>{number = 3, name = (null)}，number=30

2018-04-23 17:41:40.357313+0800 LockDemo[90636:6315707] 當(dāng)前線程：<NSThread: 0x604000464400>{number = 3, name = (null)}，number=40

2018-04-23 17:41:40.357522+0800 LockDemo[90636:6315707] 當(dāng)前線程：<NSThread: 0x604000464400>{number = 3, name = (null)}，NSLock解鎖

NSCondition

這個(gè)方法和信號(hào)量有點(diǎn)相似：

wait：進(jìn)入等待狀態(tài)
waitUntilDate:：讓一個(gè)線程等待一定的時(shí)間
signal：?jiǎn)拘岩粋€(gè)等待的線程
broadcast：?jiǎn)拘阉械却木€程

### 線程延遲執(zhí)行

上代碼：


- (void)setNSConditionUntilDate

{

 NSCondition *conditionLock = [NSCondition new];

 __block NSInteger number = 10;

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，NSCondition上鎖",[NSThread currentThread]);

 [conditionLock lock];

 [conditionLock waitUntilDate:[NSDate dateWithTimeIntervalSinceNow:3]];

 number = number + 1;

 NSLog(@"number=%ld",number);

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 [conditionLock unlock];

 });   

}

可以看到打印代碼中number=11的代碼在第一次輸出的3s之后。


2018-04-24 10:13:22.892167+0800 LockDemo[92613:6424100] 當(dāng)前線程：<NSThread: 0x600000277300>{number = 3, name = (null)}，NSCondition上鎖

2018-04-24 10:13:25.895626+0800 LockDemo[92613:6424100] number=11

2018-04-24 10:13:25.896116+0800 LockDemo[92613:6424100] 當(dāng)前線程：<NSThread: 0x600000277300>{number = 3, name = (null)}，number=11

喚醒等待線程

上代碼：


- (void)setNSConditionWait

{

 NSCondition *conditionLock = [NSCondition new];

 __block NSInteger number = 10;

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，NSCondition上鎖",[NSThread currentThread]);

 [conditionLock lock];

 [conditionLock wait];

 number = number + 10;

 NSLog(@"number=%ld",number);

 [conditionLock unlock];

 });

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，NSCondition上鎖",[NSThread currentThread]);

 [conditionLock lock];

 [conditionLock wait];

 number = number + 20;

 NSLog(@"number=%ld",number);

 [conditionLock unlock];

 });

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 sleep(2);

 NSLog(@"當(dāng)前線程：%@，NSCondition喚醒等待的線程",[NSThread currentThread]);

 [conditionLock signal];

 });

}

打印結(jié)果：


2018-04-24 10:21:48.119910+0800 LockDemo[92914:6437121] 當(dāng)前線程：<NSThread: 0x604000466d00>{number = 4, name = (null)}，NSCondition上鎖

2018-04-24 10:21:48.119911+0800 LockDemo[92914:6437122] 當(dāng)前線程：<NSThread: 0x604000466dc0>{number = 3, name = (null)}，NSCondition上鎖

2018-04-24 10:21:50.121817+0800 LockDemo[92914:6437120] 當(dāng)前線程：<NSThread: 0x6000002764c0>{number = 5, name = (null)}，NSCondition喚醒等待的線程

2018-04-24 10:21:50.122050+0800 LockDemo[92914:6437121] number=30

喚醒所有等待線程


- (void)setNSConditionBroadcast

{

 NSCondition *conditionLock = [NSCondition new];

 __block NSInteger number = 10;

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，NSCondition上鎖",[NSThread currentThread]);

 [conditionLock lock];

 [conditionLock wait];

 number = number + 10;

 NSLog(@"number=%ld",number);

 [conditionLock unlock];

 });

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 NSLog(@"當(dāng)前線程：%@，NSCondition上鎖",[NSThread currentThread]);

 [conditionLock lock];

 [conditionLock wait];

 number = number + 20;

 NSLog(@"number=%ld",number);

 [conditionLock unlock];

 });

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 sleep(2);

 NSLog(@"當(dāng)前線程：%@，NSCondition喚醒所有等待的線程",[NSThread currentThread]);

 [conditionLock broadcast];

 });

}

打印結(jié)果：


2018-04-24 10:23:26.901406+0800 LockDemo[92991:6440383] 當(dāng)前線程：<NSThread: 0x600000277480>{number = 3, name = (null)}，NSCondition上鎖

2018-04-24 10:23:26.901406+0800 LockDemo[92991:6440385] 當(dāng)前線程：<NSThread: 0x60400026d7c0>{number = 4, name = (null)}，NSCondition上鎖

2018-04-24 10:23:28.904168+0800 LockDemo[92991:6440386] 當(dāng)前線程：<NSThread: 0x60400026df40>{number = 5, name = (null)}，NSCondition喚醒所有等待的線程

2018-04-24 10:23:28.904544+0800 LockDemo[92991:6440383] number=20

2018-04-24 10:23:28.904763+0800 LockDemo[92991:6440385] number=40

@synchronized 條件鎖

@synchronized 應(yīng)該是一種比較簡(jiǎn)單的鎖。

直接上代碼：


- (void)setSynchronized

{

 __block NSInteger number = 10;

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 @synchronized (self)

 {

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 number += 10;

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 }

 });

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 @synchronized (self)

 {

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 number += 20;

 NSLog(@"當(dāng)前線程：%@，number=%ld",[NSThread currentThread],number);

 }

 });

}

打印結(jié)果：


2018-04-24 10:29:48.814631+0800 LockDemo[93300:6451071] 當(dāng)前線程：<NSThread: 0x600000467900>{number = 3, name = (null)}，number=10

2018-04-24 10:29:48.815056+0800 LockDemo[93300:6451071] 當(dāng)前線程：<NSThread: 0x600000467900>{number = 3, name = (null)}，number=20

2018-04-24 10:29:48.815291+0800 LockDemo[93300:6451070] 當(dāng)前線程：<NSThread: 0x600000468000>{number = 4, name = (null)}，number=20

2018-04-24 10:29:48.816572+0800 LockDemo[93300:6451070] 當(dāng)前線程：<NSThread: 0x600000468000>{number = 4, name = (null)}，number=40

NSConditionLock 條件鎖

這個(gè)鎖和NSLock相差不大，多了一個(gè)condition參數(shù)，可以理解為一個(gè)條件標(biāo)示。也可以實(shí)現(xiàn)任務(wù)之前的互相依賴。

放代碼：


- (void)setConditionLock

{

 NSConditionLock *condationLock = [[NSConditionLock alloc] init];

 //線程1

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 if([condationLock tryLockWhenCondition:0]){

 NSLog(@"線程1");

 [condationLock unlockWithCondition:1];

 }else{

 NSLog(@"失敗");

 }

 });

 //線程2

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 [condationLock lockWhenCondition:3];

 NSLog(@"線程2");

 [condationLock unlockWithCondition:2];

 });

 //線程3

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

 [condationLock lockWhenCondition:1];

 NSLog(@"線程3");

 [condationLock unlockWithCondition:3];

 });

}

打印結(jié)果：


2018-04-24 10:46:04.325347+0800 LockDemo[93661:6468125] 線程1

2018-04-24 10:46:04.325573+0800 LockDemo[93661:6468124] 線程3

2018-04-24 10:46:04.325775+0800 LockDemo[93661:6468122] 線程2

由上可知，我們?cè)诔跏蓟?NSConditionLock 對(duì)象時(shí)，給了他的標(biāo)示為 0；執(zhí)行 tryLockWhenCondition:時(shí)，我們傳入的條件標(biāo)示也是 0，所以線程1 加鎖成功；執(zhí)行 unlockWithCondition:時(shí)，這時(shí)候會(huì)把condition由 0 修改為 1；因?yàn)閏ondition 修改為了 1，會(huì)先走到線程3，然后線程3 又將 condition 修改為 3，最后走了線程2 的流程。

最后

以上就是全部的內(nèi)容，還是放一個(gè)demo在這里吧。

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iOS開發(fā)-iOS中的八種鎖

iOS開發(fā)-iOS中的八種鎖

OSSpinLock 自旋鎖

dispatch_semaphore 信號(hào)量

pthread_mutex 互斥鎖

pthread_mutex(recursive) 遞歸鎖

NSLock

NSCondition

喚醒等待線程

喚醒所有等待線程

@synchronized 條件鎖

NSConditionLock 條件鎖

最后

相關(guān)閱讀更多精彩內(nèi)容

友情鏈接更多精彩內(nèi)容

色偷偷精品伊人,欧洲久久精品,欧美综合婷婷骚逼,国产AV主播,国产最新探花在线,九色在线视频一区,伊人大交九 欧美,1769亚洲,黄色成人av

iOS開發(fā)-iOS中的八種鎖

OSSpinLock 自旋鎖

dispatch_semaphore 信號(hào)量

pthread_mutex 互斥鎖

pthread_mutex(recursive) 遞歸鎖

NSLock

NSCondition

喚醒等待線程

喚醒所有等待線程

@synchronized 條件鎖

NSConditionLock 條件鎖

最后

相關(guān)閱讀更多精彩內(nèi)容

友情鏈接更多精彩內(nèi)容

色偷偷精品伊人,欧洲久久精品,欧美综合婷婷骚逼,国产AV主播,国产最新探花在线,九色在线视频一区,伊人大交九欧美,1769亚洲,黄色成人av