一、创建线程

1、方法一

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

- (void)threadSelectorDYZ{
    NSLog(@"%s",__FUNCTION__);
}

2、方法二

    NSThread *thread = [[NSThread alloc] initWithBlock:^{
        NSLog(@"%s",__FUNCTION__);
    }];
    [thread start];

3、方法三

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

- (void)threadSelectorDYZ{
    NSLog(@"%s",__FUNCTION__);
}

4、方法四

    [NSThread detachNewThreadWithBlock:^{
        NSLog(@"%s",__FUNCTION__);
    }];

5、隐私方法创建线程

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

- (void)threadSelectorDYZ{
    NSLog(@"%s",__FUNCTION__);
}

二、perform

2.1、执行方法，当前是什么线程就在什么线程执行

下面三个方法在NSObject中

• - (id)performSelector:(SEL)aSelector;
• - (id)performSelector:(SEL)aSelector withObject:(id)object;
• - (id)performSelector:(SEL)aSelector withObject:(id)object1 withObject:(id)object2;

- (void)test {
    NSLog(@"test:%@",[NSThread currentThread]);
}

- (void)testOne:(NSArray *)str {
    NSLog(@"testOne:%@\n%@",[NSThread currentThread],str);
}

- (void)testTwo:(NSArray *)str with:(NSString *)str1{
    NSLog(@"testTwo:%@\n%@\n%@",[NSThread currentThread],str,str1);
}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [self performSelector:@selector(test)];
    [self performSelector:@selector(testOne:) withObject:@[@"123",@"234",@"345"]];
    [self performSelector:@selector(testTwo:with:) withObject:@[@"123",@"234",@"345"] withObject:@"hello world"];
}

2020-04-23 13:48:40.876108+0800 TraceDemo[13692:1917162] test:<NSThread: 0x281782f40>{number = 1, name = main}
2020-04-23 13:48:40.876402+0800 TraceDemo[13692:1917162] testOne:<NSThread: 0x281782f40>{number = 1, name = main}
(
    123,
    234,
    345
)
2020-04-23 13:48:40.876639+0800 TraceDemo[13692:1917162] testTwo:<NSThread: 0x281782f40>{number = 1, name = main}
(
    123,
    234,
    345
)
hello world

2.2、 线程切换，到主线程、指定线程、后台线程(子线程)执行

下面五个方法属于NSThreadPerformAdditions分类

- (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 API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));
- (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));
    // equivalent to the first method with kCFRunLoopCommonModes
- (void)performSelectorInBackground:(SEL)aSelector withObject:(nullable id)arg API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));

2.3、延迟调用，在当前线程延迟调用

如果是主线程不会堵住当前线程，子线程会堵住当前线程

• - (void)performSelector:(SEL)aSelector withObject:(nullable id)anArgument afterDelay:(NSTimeInterval)delay;

三、[[NSRunLoop currentRunLoop] run]

• 如果是主线程，run后面的代码都不会走了。

• 如果是子线程，run前面如果有定时器time，run后面的代码也不会走，定时器执行完毕了，就可以走了；run前面如果没有定时器time，run后面的代码会走

• 总结：当有任务执行的时候，run后面的代码就不会走，没有任务执行了，run后面的代码就会走了。那么为什么主线程run后面的代码不会走呢，是因为主线程干其他的事去了，只是你不知道而已。

.