iOS之创建一个常驻线程

// 当创建一个线程，并且希望它一直存在时，但往往我们创建的线程都是执行完成之后也就停止了，不能再次利用，那么如何创建一个线程可以让他可以再次工作呢,这个时候就需要使用到RunLoop了。下面的是我写的一个例子：
#import "LongThreadDemoController.h"

@interface LongThreadDemoController ()
@property (nonatomic, strong) NSThread *thread;

@end

@implementation LongThreadDemoController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    self.title = @"常驻线程Demo";

}

- (void)threadRunloopPoint:(id)__unused object{
    NSLog(@"%@",NSStringFromSelector(_cmd));
    @autoreleasepool {
        [[NSThread currentThread] setName:@"changzhuThread"];
        NSRunLoop *runLoop = [NSRunLoop currentRunLoop];
        //// 这里主要是监听某个 port，目的是让这个 Thread 不会回收
        [runLoop addPort:[NSMachPort port] forMode:NSDefaultRunLoopMode];
        [runLoop run];
    }
}

- (NSThread *)thread{

    if(!_thread){
        _thread = [[NSThread alloc] initWithTarget:self selector:@selector(threadRunloopPoint:) object:nil];
        [_thread start];
    }
    return _thread;

}

- (void)test{

    NSLog(@"%s",__func__);
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{

    [self performSelector:@selector(test) onThread:self.thread withObject:nil waitUntilDone:NO modes:@[NSDefaultRunLoopMode]];

}