線程阻塞問題-功能：環信登陸失敗後自動登陸5次

項目中集成了環信，點擊聯繫客服時須要調取環信的接口，如今有個要求，若是調取環信的登陸接口失敗了，就要從新登陸，可是這個操做不能影響主線程的操做，登陸次數達到必定的數量後中止登陸。
首先：環信的登陸時同步的，須要咱們開啓一個線程，否則當環信登陸失敗時會很容易形成界面卡死的狀況。
+ (void)loginWithSuccessBlock:(void(^)())success FailureBlock:(void(^)())failure{   // 本身封裝的一個公共類

    // 開啓一個線程防止登陸失敗時形成主線程卡死

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

    [q addOperationWithBlock:^{

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

        // 主線程更新UI

        [[NSOperationQueue mainQueue] addOperationWithBlock:^{

            if (!error)

            {

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

                success();

            }else{

                failure();   // 登陸失敗調取另外一個方法繼續嘗試登陸，登陸5次中止登陸

                [[[self alloc] init] HXLoginFailed];

            }

       }];

    }];

}

而後就是登陸失敗  開啓一個線程繼續登陸，登陸5次後中止登陸

- (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 {
        
    }
}
------------------------------------------------------------------------華麗分割線---------------------------------------------------------------------------------------------
最後看看NSOperation怎麼實現

原理：只要將一個NSOperation（實際開中須要使用其子類NSInvocationOperation、NSBlockOperation）放到NSOperationQueue這個隊列中線程就會依次啓動。

NSOperation有兩個經常使用子類用於建立線程操做：NSInvocationOperation和NSBlockOperation，兩種方式本質沒有區別，可是是後者使用Block形式進行代碼組織，使用相對方便。
- (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{
    // 開啓一個線程防止登陸失敗時形成主線程卡死
    NSOperationQueue *q = [[NSOperationQueue alloc]init];
    [q addOperationWithBlock:^{
        EMError *error = [[EMClient sharedClient] loginWithUsername:USER_NAME password:@"jimaijie654321"];
        // 主線程更新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"];
        // 主線程更新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];
            }
        }];
    }];

}