示意圖.png

1、優(yōu)缺點(diǎn)

1.優(yōu)點(diǎn)：NSThread比其他兩種多線程方案較輕量級(jí)，更直觀地控制線程對(duì)象
2.缺點(diǎn)：需要自己管理線程的生命周期，線程同步。線程同步對(duì)數(shù)據(jù)的加鎖會(huì)有一定的系統(tǒng)開(kāi)銷

2、 NSThread相關(guān)的主要方法：

創(chuàng)建、啟動(dòng)線程

  // 線程一啟動(dòng)，就會(huì)在線程thread中執(zhí)行self的run方法

NSThread *thread = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];

[thread start];

創(chuàng)建線程后自動(dòng)啟動(dòng)線程

[NSThread detachNewThreadSelector:@selector(test) toTarget:self withObject:nil];

隱式創(chuàng)建并啟動(dòng)線程

[self performSelectorInBackground:@selector(run) withObject:nil];

3、互斥鎖

@synchronized(鎖對(duì)象) { // 需要鎖定的代碼 }

互斥鎖的優(yōu)缺點(diǎn)
優(yōu)點(diǎn)：能有效防止因多線程搶奪資源造成的數(shù)據(jù)安全問(wèn)題
缺點(diǎn)：需要消耗大量的CPU資源

互斥鎖的使用前提：多條線程搶奪同一塊資源

4、線程間通信

線程間通信常用方法

- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait;

- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(id)arg waitUntilDone:(BOOL)wait;

5、模擬一個(gè)賣票系統(tǒng)

self.tickets = 100;//總共票數(shù)

NSThread *thread1 = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];
thread1.name = @"售票機(jī)1";
[thread1 start];

NSThread *thread2 = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];
thread2.name = @"售票機(jī)2";
[thread2 start];



- (void)run {

    if (_lock == nil)
    {
        _lock = [[NSLock alloc] init];
    }

    while (YES)
    {
        [_lock lock];
        if (_tickets > 0)
        {
            _tickets -= 1;
            NSString *message = [NSString stringWithFormat:@"當(dāng)前票數(shù)是%ld，售票線程是%@",(long)_tickets,[[NSThread currentThread] name]];

            NSLog(@"message == %@",message);
        
            [_lock unlock];
        
            if ([[[NSThread currentThread] name] isEqualToString:@"售票機(jī)1"])
            {
                [NSThread sleepForTimeInterval:0.2];
            }
            else
                [NSThread sleepForTimeInterval:0.3];
        }
        else
        {
            [_lock unlock];
            break;
        }
    }
}