一、NSCondition 与 NSConditionLock

1、NSCondition 需要外部定义条件变量
2、NSConditionLock 自带条件，如：

self.conditionLock = [[NSConditionLock alloc] initWithCondition:10];
[self.conditionLock lockWhenCondition:10];

二、条件锁的使用

1、NSConditionLock

NSConditionLock * conditionLock = [[NSConditionLock alloc] initWithCondition:10];
//当条件为9时，不会向下执行
[conditionLock lockWhenCondition:10];
//code
[conditionLock unlockWithCondition:10];

2、NSCondition

- (void)viewBlock{
    [NSThread detachNewThreadSelector:@selector(threadEvent:) toTarget:self withObject:nil];
}
- (void)threadEvent:(id)thread{
    _condition = [[NSCondition alloc] init];
    //等待
    [_condition wait];
    NSLog(@"event finished");
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    [_condition signal];
}