线程阻塞问题-功能：环信登陆失败后自动登陆5次

项目中集成了环信，点击联系客服时须要调取环信的接口，如今有个要求，若是调取环信的登陆接口失败了，就要从新登陆，可是这个操做不能影响主线程的操做，登陆次数达到必定的数量后中止登陆。
首先：环信的登陆时同步的，须要咱们开启一个线程，否则当环信登陆失败时会很容易形成界面卡死的状况。
+ (void)loginWithSuccessBlock:(void(^)())success FailureBlock:(void(^)())failure{   // 本身封装的一个公共类

    // 开启一个线程防止登陆失败时形成主线程卡死

    NSOperationQueue *q = [[NSOperationQueue alloc]init];

    [q addOperationWithBlock:^{

        EMError *error = [[EMClient sharedClient] loginWithUsername:USER_NAME password:@"123456"];

        // 主线程更新UI

        [[NSOperationQueue mainQueue] addOperationWithBlock:^{

            if (!error)

            {

                [[EMClient sharedClient].options setIsAutoLogin:YES];

                success();

            }else{

                failure();   // 登陆失败调取另外一个方法继续尝试登陆，登陆5次中止登陆

                [[[self alloc] init] HXLoginFailed];

            }

       }];

    }];

}

而后就是登陆失败  开启一个线程继续登陆，登陆5次后中止登陆

- (void)HXLoginFailed
{
    [self.thread cancel];
    self.thread = nil;
    NSString* countStr = [SKUserDefaults valueForKey:@"HXCount"];
    if ([countStr intValue]>5) {
        return;
    }
    DLog(@"========%@=====%d",[NSThread currentThread],[countStr intValue]);
    self.thread=[[NSThread alloc]initWithTarget:self selector:@selector(HXLoginFailed2) object:nil];
    [self.thread start];
    self.requestCount++;
}
- (void)HXLoginFailed2
{
    EMError *error = [[EMClient sharedClient] loginWithUsername:USER_NAME password:@"123456"];
    if (error) {
        NSString* countStr = [SKUserDefaults valueForKey:@"HXCount"];
        countStr = [NSString stringWithFormat:@"%d",[countStr intValue]+1];
        [SKUserDefaults setValue:countStr forKey:@"HXCount"];
        [self HXLoginFailed];
    } else {
        
    }
}
------------------------------------------------------------------------华丽分割线---------------------------------------------------------------------------------------------
最后看看NSOperation怎么实现

原理：只要将一个NSOperation（实际开中须要使用其子类NSInvocationOperation、NSBlockOperation）放到NSOperationQueue这个队列中线程就会依次启动。

NSOperation有两个经常使用子类用于建立线程操做：NSInvocationOperation和NSBlockOperation，两种方式本质没有区别，可是是后者使用Block形式进行代码组织，使用相对方便。
- (instancetype)init
{
    self = [super init];
    if (self) {
        self.OperationQueue = [[NSOperationQueue alloc]init];
        self.OperationQueue.maxConcurrentOperationCount = 1;
    }
    return self;
}

+ (void)loginWithSuccessBlock:(void(^)())success FailureBlock:(void(^)())failure{
    // 开启一个线程防止登陆失败时形成主线程卡死
    NSOperationQueue *q = [[NSOperationQueue alloc]init];
    [q addOperationWithBlock:^{
        EMError *error = [[EMClient sharedClient] loginWithUsername:USER_NAME password:@"jimaijie654321"];
        // 主线程更新UI
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            if (!error)
            {
                [[EMClient sharedClient].options setIsAutoLogin:YES];
                success();
            }else{
                failure();
                [SKUserDefaults setValue:@"0" forKey:@"HXCount"];
                [[[self alloc] init] HXLoginFailed];
            }
        }];
    }];
}

- (void)HXLoginFailed
{
    NSString* countStr = [SKUserDefaults valueForKey:@"HXCount"];
    if ([countStr intValue]>5) {
        self.OperationQueue = nil;
        return;
    }
    DLog(@"========%@=====%d",[NSThread currentThread],[countStr intValue]);
    [self.OperationQueue addOperationWithBlock:^{
        DLog(@"+++++++++++++%@=====%d",[NSThread currentThread],[countStr intValue]);
        EMError *error = [[EMClient sharedClient] loginWithUsername:USER_NAME password:@"jimaijie654321"];
        // 主线程更新UI
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            if (!error)
            {
                [[EMClient sharedClient].options setIsAutoLogin:YES];
            }else{
                NSString* countStr = [SKUserDefaults valueForKey:@"HXCount"];
                countStr = [NSString stringWithFormat:@"%d",[countStr intValue]+1];
                [SKUserDefaults setValue:countStr forKey:@"HXCount"];
                [self HXLoginFailed];
            }
        }];
    }];

}