iOS利用多線程進行網(wǎng)絡(luò)請求

1.前言

這兩天忙著對付Other-Other的問題哀墓，今天才抽空給APP新增了一個離線緩存的功能，由于我的APP是對書源進行轉(zhuǎn)碼格式化閱讀，所以緩存這里是個很頭疼的問題根暑，稍不慎就會503.目前的方案就是動態(tài)切換UA和利用多線程 一章一章下 收到失敗就等待一會再繼續(xù)魂拦，目前測試沒什么問題。

2.多線程緩存

+ (void)downloadChaptersContentWithBookModel:(TJBookModel *)bookModel chapterIds:(NSArray *)chapterIds progress:(void (^)(NSInteger progress)) progress complete:(nullable void (^)(BOOL, NSString * _Nonnull, NSArray * _Nullable))complete {
    if (TJIsEmptyObject(bookModel.bookId)) {
        !complete ?: complete(NO, @"未知書籍", nil);
    }
    if (chapterIds.count == 0) {
        !complete ?: complete(NO, @"未知章節(jié)", nil);
    }
    // 統(tǒng)計下載章節(jié)數(shù)量
    __block NSInteger downloadCount = 0;
    // 統(tǒng)計下載失敗章節(jié)ID
    __block NSMutableArray *failureArray = [[NSMutableArray alloc] init];
    
    
    //創(chuàng)建串行隊列
    dispatch_queue_t customQuue = dispatch_queue_create("cpm.apolla.download", DISPATCH_QUEUE_SERIAL);
     //創(chuàng)建信號量并初始化總量為1
    dispatch_semaphore_t semaphoreLock = dispatch_semaphore_create(0);
    //添加任務(wù)
    dispatch_async(customQuue, ^{


        for (NSString *chapterId in chapterIds) {
            if (TJIsEmptyObject(chapterId)) {
                downloadCount += 1;
                if (downloadCount == chapterIds.count) {
                    !complete ?: complete(YES, @"下載完成", failureArray);
                } else {
                    !progress ?: progress(downloadCount);
                }
                continue;
            }


                [self chapterWithBookModel:bookModel chapterId:chapterId success:^(TJChapterModel * _Nonnull chapter) {
                    downloadCount +=1;
                    !progress ?: progress(downloadCount);
                    //緩存成功就0.5s后繼續(xù)緩存
                    dispatch_time_t timer = dispatch_time(DISPATCH_TIME_NOW, 0.5 * NSEC_PER_SEC);

                    dispatch_after(timer, dispatch_get_main_queue(), ^{

  //相當于解鎖                      dispatch_semaphore_signal(semaphoreLock);

                    });


                } failure:^(NSString * _Nonnull tip) {
                    downloadCount+=1;
                    // 保存失敗章節(jié)ID
                    [failureArray addObject:chapterId];
                    !progress ?: progress(downloadCount);
                    //緩存失敗就5秒回再緩存
                    dispatch_time_t timer = dispatch_time(DISPATCH_TIME_NOW, 5 * NSEC_PER_SEC);

                    dispatch_after(timer, dispatch_get_main_queue(), ^{

    //解鎖                    dispatch_semaphore_signal(semaphoreLock);

                    });
                }];
                //加鎖
//使用 DISPATCH_TIME_FOREVER 要注意線程問題 可能會造成APP卡死做瞪，我這里是因為作為網(wǎng)絡(luò)請求 肯定會有結(jié)果返回对粪，所以問題不大
            dispatch_semaphore_wait(semaphoreLock, DISPATCH_TIME_FOREVER);

        }


        dispatch_async(dispatch_get_main_queue(), ^{
        complete(YES, @"下載完成", failureArray);
        });
    });
  
}

3.錯誤的使用

想抄代碼的這段不用看，我最開始用GCDGroup作為管理的装蓬，但是不知道為啥會控制不住請求衩侥，有大神可以為小弟解讀下不

+ (void)downloadChaptersContentWithBookModel:(TJBookModel *)bookModel chapterIds:(NSArray *)chapterIds progress:(void (^)(NSInteger progress)) progress complete:(nullable void (^)(BOOL, NSString * _Nonnull, NSArray * _Nullable))complete {
    if (TJIsEmptyObject(bookModel.bookId)) {
        !complete ?: complete(NO, @"未知書籍", nil);
    }
    if (chapterIds.count == 0) {
        !complete ?: complete(NO, @"未知章節(jié)", nil);
    }
    // 統(tǒng)計下載章節(jié)數(shù)量
    __block NSInteger downloadCount = 0;
    // 統(tǒng)計下載失敗章節(jié)ID
    __block NSMutableArray *failureArray = [[NSMutableArray alloc] init];
    
    
    dispatch_group_t group =  dispatch_group_create();
    dispatch_queue_t queue = dispatch_queue_create("com.wumeng.network", DISPATCH_QUEUE_SERIAL);
    for (NSString *chapterId in chapterIds) {
        if (TJIsEmptyObject(chapterId)) {
            downloadCount += 1;
            if (downloadCount == chapterIds.count) {
                !complete ?: complete(YES, @"下載完成", failureArray);
            } else {
                !progress ?: progress(downloadCount);
            }
            continue;
        }
        dispatch_group_enter(group);
        dispatch_group_async(group,queue, ^{
            [self chapterWithBookModel:bookModel chapterId:chapterId success:^(TJChapterModel * _Nonnull chapter) {
                downloadCount +=1;
                dispatch_time_t timer = dispatch_time(DISPATCH_TIME_NOW, 0.5 * NSEC_PER_SEC);
                dispatch_after(timer, queue, ^{
                    !progress ?: progress(downloadCount);
                    dispatch_group_leave(group);

                });

            } failure:^(NSString * _Nonnull tip) {
                downloadCount+=1;
                // 保存失敗章節(jié)ID
                [failureArray addObject:chapterId];
                dispatch_time_t timer = dispatch_time(DISPATCH_TIME_NOW, 5 * NSEC_PER_SEC);
                dispatch_after(timer, queue, ^{
                    !progress ?: progress(downloadCount);
                    dispatch_group_leave(group);

                });
            }];
        });
    }



    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        complete(YES, @"下載完成", failureArray);
    });

    
}

4.動態(tài)切換UA

其實思路很簡單，動態(tài)設(shè)置User-Agent

    NSArray *uas = @[
        @"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; AcooBrowser; .NET CLR 1.1.4322; .NET CLR 2.0.50727)",
        @"Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; Acoo Browser; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.04506)",
        @"Mozilla/4.0 (compatible; MSIE 7.0; AOL 9.5; AOLBuild 4337.35; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)",
        @"Mozilla/5.0 (Windows; U; MSIE 9.0; Windows NT 9.0; en-US)",
        @"Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Win64; x64; Trident/5.0; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET CLR 2.0.50727; Media Center PC 6.0)",
        @"Mozilla/5.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET CLR 1.0.3705; .NET CLR 1.1.4322)",
        @"Mozilla/4.0 (compatible; MSIE 7.0b; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727; InfoPath.2; .NET CLR 3.0.04506.30)",
        @"Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN) AppleWebKit/523.15 (KHTML, like Gecko, Safari/419.3) Arora/0.3 (Change: 287 c9dfb30)",
        @"Mozilla/5.0 (X11; U; Linux; en-US) AppleWebKit/527+ (KHTML, like Gecko, Safari/419.3) Arora/0.6",
        @"Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.2pre) Gecko/20070215 K-Ninja/2.1.1",
        @"Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9) Gecko/20080705 Firefox/3.0 Kapiko/3.0",
        @"Mozilla/5.0 (X11; Linux i686; U;) Gecko/20070322 Kazehakase/0.4.5",
        @"Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.8) Gecko Fedora/1.9.0.8-1.fc10 Kazehakase/0.5.6",
        @"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.56 Safari/535.11",
        @"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3) AppleWebKit/535.20 (KHTML, like Gecko) Chrome/19.0.1036.7 Safari/535.20",
        @"Opera/9.80 (Macintosh; Intel Mac OS X 10.6.8; U; fr) Presto/2.9.168 Version/11.52",
        @"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.11 TaoBrowser/2.0 Safari/536.11",
        @"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.71 Safari/537.1 LBBROWSER",
        @"Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; LBBROWSER)",
        @"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 732; .NET4.0C; .NET4.0E; LBBROWSER)",
        @"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.84 Safari/535.11 LBBROWSER",
        @"Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E)",
        @"Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; QQBrowser/7.0.3698.400)",
        @"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 732; .NET4.0C; .NET4.0E)",
        @"Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; SV1; QQDownload 732; .NET4.0C; .NET4.0E; 360SE)",
        @"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 732; .NET4.0C; .NET4.0E)",
        @"Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E)",
        @"Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1",
        @"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1",
        @"Mozilla/5.0 (iPad; U; CPU OS 4_2_1 like Mac OS X; zh-cn) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8C148 Safari/6533.18.5",
        @"Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:2.0b13pre) Gecko/20110307 Firefox/4.0b13pre",
        @"Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:16.0) Gecko/20100101 Firefox/16.0",
        @"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.64 Safari/537.11",
        @"Mozilla/5.0 (X11; U; Linux x86_64; zh-CN; rv:1.9.2.10) Gecko/20100922 Ubuntu/10.10 (maverick) Firefox/3.6.10"
    ];
    [self.manager.requestSerializer setValue:uas[(arc4random() % [uas count])] forHTTPHeaderField:@"User-Agent"];

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