YTKNetwork源码解析2

作者: p_peng | 来源:发表于2019-06-29 16:31 被阅读0次

YTKNetwork在GitHub的仓库中有一份高级教程，这篇我们就来看下高级教程中相关部分的源码。

YTKUrlFilterProtocol 接口

这个只是一个接口，需要实现下面的方法，可以为originUrl拼接额外的一些信息。

- (NSString *)filterUrl:(NSString *)originUrl withRequest:(YTKBaseRequest *)request;

Demo工程中提供了一种实现YTKUrlArgumentsFilter，通过一个NSDictionary初始化，使用AFNetworking的方法AFQueryStringFromParameters把NSDictionary转成NSString拼接到originUrlString后面。这个实现是用queryString的形式，也可以添加到header中，这就看具体的实现了。

YTKBatchRequest

批量请求，Demo中有例子：

- (void)sendBatchRequest {
    GetImageApi *a = [[GetImageApi alloc] initWithImageId:@"1.jpg"];
    GetImageApi *b = [[GetImageApi alloc] initWithImageId:@"2.jpg"];
    GetImageApi *c = [[GetImageApi alloc] initWithImageId:@"3.jpg"];
    GetUserInfoApi *d = [[GetUserInfoApi alloc] initWithUserId:@"123"];
    YTKBatchRequest *batchRequest = [[YTKBatchRequest alloc] initWithRequestArray:@[a, b, c, d]];
    [batchRequest startWithCompletionBlockWithSuccess:^(YTKBatchRequest *batchRequest) {
        NSLog(@"succeed");
        NSArray *requests = batchRequest.requestArray;
        GetImageApi *a = (GetImageApi *)requests[0];
        GetImageApi *b = (GetImageApi *)requests[1];
        GetImageApi *c = (GetImageApi *)requests[2];
        GetUserInfoApi *user = (GetUserInfoApi *)requests[3];
        // deal with requests result ...
        NSLog(@"%@, %@, %@, %@", a, b, c, user);
    } failure:^(YTKBatchRequest *batchRequest) {
        NSLog(@"failed");
    }];
}

首先创建多个网络请求，把他们加到一个数组中，使用这个数组初始化一个YTKBatchRequest批量请求，设置回调方式，并开始请求。

- (void)start {
    if (_finishedCount > 0) {
        YTKLog(@"Error! Batch request has already started.");
        return;
    }
    _failedRequest = nil;
    [[YTKBatchRequestAgent sharedAgent] addBatchRequest:self];
    [self toggleAccessoriesWillStartCallBack];
    // 直接遍历所有请求，调用start方法开始请求
    for (YTKRequest * req in _requestArray) {
        req.delegate = self;
        [req clearCompletionBlock];
        [req start];
    }
}

本来我以为是用dispatch_group_t实现的，结果一看源码，很简单，在请求回调的地方维护了一个count，等count等于初始化时请求的数量时，就说明请求全部成功了。

- (void)requestFinished:(YTKRequest *)request {
    _finishedCount++;
    if (_finishedCount == _requestArray.count) {
        [self toggleAccessoriesWillStopCallBack];
        if ([_delegate respondsToSelector:@selector(batchRequestFinished:)]) {
            [_delegate batchRequestFinished:self];
        }
        if (_successCompletionBlock) {
            _successCompletionBlock(self);
        }
        [self clearCompletionBlock];
        [self toggleAccessoriesDidStopCallBack];
        [[YTKBatchRequestAgent sharedAgent] removeBatchRequest:self];
    }
}

疑问

这里其实我有两点疑问：

这里的_finishedCount++是否需要加锁，因为返回的队列是一个DISPATCH_QUEUE_CONCURRENT队列，有可能会有多个请求同时返回，这里会不会有问题？
YTKBatchRequestAgent的作用是什么，我理解的只是为了防止这个batchRequest被release。不知道这样理解对不对？

如果有同学知道，还望留言指教。

YTKChainRequest

chain是链的意思，YTKChainRequest用于管理有相互依赖的网络请求。有些请求需要依赖前面的请求，这时候就需要用到YTKChainRequest，把请求加到chainReq中，并加上回调处理。

- (void)sendChainRequest {
    RegisterApi *reg = [[RegisterApi alloc] initWithUsername:@"username" password:@"password"];
    YTKChainRequest *chainReq = [[YTKChainRequest alloc] init];
    [chainReq addRequest:reg callback:^(YTKChainRequest *chainRequest, YTKBaseRequest *baseRequest) {
        RegisterApi *result = (RegisterApi *)baseRequest;
        NSString *userId = [result userId];
        GetUserInfoApi *api = [[GetUserInfoApi alloc] initWithUserId:userId];
        [chainRequest addRequest:api callback:nil];
    }];
    chainReq.delegate = self;
    // start to send request
    [chainReq start];
}

在方法- (void)addRequest:(YTKBaseRequest *)request callback:(YTKChainCallback)callback;中只是简单的把请求和回调加到数组中。调用- (void)start;方法后从数组的第一个请求开始执行。

- (void)start {
    if (_nextRequestIndex > 0) {
        YTKLog(@"Error! Chain request has already started.");
        return;
    }

    if ([_requestArray count] > 0) {
        [self toggleAccessoriesWillStartCallBack];
        [self startNextRequest];
        [[YTKChainRequestAgent sharedAgent] addChainRequest:self];
    } else {
        YTKLog(@"Error! Chain request array is empty.");
    }
}

- (BOOL)startNextRequest {
    if (_nextRequestIndex < [_requestArray count]) {
        YTKBaseRequest *request = _requestArray[_nextRequestIndex];
        _nextRequestIndex++;
        request.delegate = self;
        [request clearCompletionBlock];
        [request start];
        return YES;
    } else {
        return NO;
    }
}

上面添加请求的时候有两个数组，一个保存请求，一个保存回调block，这里使用了一个index来管理，发出请求后，index➕1，delegate回调方法中执行回调数组对应index的block(如果添加的时候这个block是nil，使用一个空的block放到数组中占位)。有点绕哈，请求的时候会把回调方式设置为delegate方式，并清除block回调。

YTKBaseRequest *request = _requestArray[_nextRequestIndex];
_nextRequestIndex++;
request.delegate = self;
[request clearCompletionBlock];
[request start];

疑问：如果有多个请求，这里是否会有多个block嵌套？

加载缓存的请求

有一些请求，结果返回后我们会进行缓存，下次再进入某个页面时，我们先展示缓存数据，再进行网络请求，返回后更新缓存和界面。这种情况就可以用到下面这个例子了。

- (void)loadCacheData {
    NSString *userId = @"1";
    GetUserInfoApi *api = [[GetUserInfoApi alloc] initWithUserId:userId];
    if ([api loadCacheWithError:nil]) {
        NSDictionary *json = [api responseJSONObject];
        NSLog(@"json = %@", json);
        // 先显示缓存数据
    }
    [api startWithCompletionBlockWithSuccess:^(YTKBaseRequest *request) {
        //Api中已经设置了缓存信息，所以缓存任务不用再这里处理，只需要更新UI
        NSLog(@"update ui");
    } failure:^(YTKBaseRequest *request) {
        NSLog(@"failed");
    }];
}

前面一篇已经说过，只要继承YTKRequest，并且实现- (NSInteger)cacheTimeInSeconds;方法，返回一个大于0的时间，就会把请求结果缓存到本地。loadCacheWithError:会尝试从缓存中恢复数据，数据分为元数据(metaData)和结果数据。元数据中有创建时间，版本等信息，在网络请求返回时保存到NSKeyValueArchiver中，恢复的时候使用unarchiveObjectWithFile方法进行恢复，验证时间，版本号等有效后恢复结果数据，并返回。

// 缓存请求结果
- (void)saveResponseDataToCacheFile:(NSData *)data {
    if ([self cacheTimeInSeconds] > 0 && ![self isDataFromCache]) {
        if (data != nil) {
            @try {
                // New data will always overwrite old data.
                [data writeToFile:[self cacheFilePath] atomically:YES];

                YTKCacheMetadata *metadata = [[YTKCacheMetadata alloc] init];
                metadata.version = [self cacheVersion];
                metadata.sensitiveDataString = ((NSObject *)[self cacheSensitiveData]).description;
                metadata.stringEncoding = [YTKNetworkUtils stringEncodingWithRequest:self];
                metadata.creationDate = [NSDate date];
                metadata.appVersionString = [YTKNetworkUtils appVersionString];
                [NSKeyedArchiver archiveRootObject:metadata toFile:[self cacheMetadataFilePath]];
            } @catch (NSException *exception) {
                YTKLog(@"Save cache failed, reason = %@", exception.reason);
            }
        }
    }
}
// 恢复请求结果
- (BOOL)loadCacheWithError:(NSError * _Nullable __autoreleasing *)error {
    // Make sure cache time in valid.
    if ([self cacheTimeInSeconds] < 0) {
        if (error) {
            *error = [NSError errorWithDomain:YTKRequestCacheErrorDomain code:YTKRequestCacheErrorInvalidCacheTime userInfo:@{ NSLocalizedDescriptionKey:@"Invalid cache time"}];
        }
        return NO;
    }

    // Try load metadata.
    if (![self loadCacheMetadata]) {
        if (error) {
            *error = [NSError errorWithDomain:YTKRequestCacheErrorDomain code:YTKRequestCacheErrorInvalidMetadata userInfo:@{ NSLocalizedDescriptionKey:@"Invalid metadata. Cache may not exist"}];
        }
        return NO;
    }

    // Check if cache is still valid.
    if (![self validateCacheWithError:error]) {
        return NO;
    }

    // Try load cache.
    if (![self loadCacheData]) {
        if (error) {
            *error = [NSError errorWithDomain:YTKRequestCacheErrorDomain code:YTKRequestCacheErrorInvalidCacheData userInfo:@{ NSLocalizedDescriptionKey:@"Invalid cache data"}];
        }
        return NO;
    }

    return YES;
}

- (BOOL)validateCacheWithError:(NSError * _Nullable __autoreleasing *)error {
    // Date
    NSDate *creationDate = self.cacheMetadata.creationDate;
    NSTimeInterval duration = -[creationDate timeIntervalSinceNow];
    if (duration < 0 || duration > [self cacheTimeInSeconds]) {
        if (error) {
            *error = [NSError errorWithDomain:YTKRequestCacheErrorDomain code:YTKRequestCacheErrorExpired userInfo:@{ NSLocalizedDescriptionKey:@"Cache expired"}];
        }
        return NO;
    }
    // Version
    long long cacheVersionFileContent = self.cacheMetadata.version;
    if (cacheVersionFileContent != [self cacheVersion]) {
        if (error) {
            *error = [NSError errorWithDomain:YTKRequestCacheErrorDomain code:YTKRequestCacheErrorVersionMismatch userInfo:@{ NSLocalizedDescriptionKey:@"Cache version mismatch"}];
        }
        return NO;
    }
    // Sensitive data
    NSString *sensitiveDataString = self.cacheMetadata.sensitiveDataString;
    NSString *currentSensitiveDataString = ((NSObject *)[self cacheSensitiveData]).description;
    if (sensitiveDataString || currentSensitiveDataString) {
        // If one of the strings is nil, short-circuit evaluation will trigger
        if (sensitiveDataString.length != currentSensitiveDataString.length || ![sensitiveDataString isEqualToString:currentSensitiveDataString]) {
            if (error) {
                *error = [NSError errorWithDomain:YTKRequestCacheErrorDomain code:YTKRequestCacheErrorSensitiveDataMismatch userInfo:@{ NSLocalizedDescriptionKey:@"Cache sensitive data mismatch"}];
            }
            return NO;
        }
    }
    // App version
    NSString *appVersionString = self.cacheMetadata.appVersionString;
    NSString *currentAppVersionString = [YTKNetworkUtils appVersionString];
    if (appVersionString || currentAppVersionString) {
        if (appVersionString.length != currentAppVersionString.length || ![appVersionString isEqualToString:currentAppVersionString]) {
            if (error) {
                *error = [NSError errorWithDomain:YTKRequestCacheErrorDomain code:YTKRequestCacheErrorAppVersionMismatch userInfo:@{ NSLocalizedDescriptionKey:@"App version mismatch"}];
            }
            return NO;
        }
    }
    return YES;
}

- (BOOL)loadCacheMetadata {
    NSString *path = [self cacheMetadataFilePath];
    NSFileManager * fileManager = [NSFileManager defaultManager];
    if ([fileManager fileExistsAtPath:path isDirectory:nil]) {
        @try {
            _cacheMetadata = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
            return YES;
        } @catch (NSException *exception) {
            YTKLog(@"Load cache metadata failed, reason = %@", exception.reason);
            return NO;
        }
    }
    return NO;
}

- (BOOL)loadCacheData {
    NSString *path = [self cacheFilePath];
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSError *error = nil;

    if ([fileManager fileExistsAtPath:path isDirectory:nil]) {
        NSData *data = [NSData dataWithContentsOfFile:path];
        _cacheData = data;
        _cacheString = [[NSString alloc] initWithData:_cacheData encoding:self.cacheMetadata.stringEncoding];
        switch (self.responseSerializerType) {
            case YTKResponseSerializerTypeHTTP:
                // Do nothing.
                return YES;
            case YTKResponseSerializerTypeJSON:
                _cacheJSON = [NSJSONSerialization JSONObjectWithData:_cacheData options:(NSJSONReadingOptions)0 error:&error];
                return error == nil;
            case YTKResponseSerializerTypeXMLParser:
                _cacheXML = [[NSXMLParser alloc] initWithData:_cacheData];
                return YES;
        }
    }
    return NO;
}

定制 buildCustomUrlRequest

调用YTKNetworkAgent的addRequest:方法时，会判断自定义的请求是否实现了buildCustomUrlRequest，如果返回不为nil，则直接使用返回的NSURLSessionTask进行请求。这里是为了有一些特殊的请求而做的定制需求。比如下面的例子，gzippingData上传数据：

- (NSURLRequest *)buildCustomUrlRequest {
    NSData *rawData = [[_events jsonString] dataUsingEncoding:NSUTF8StringEncoding];
    NSData *gzippingData = [NSData gtm_dataByGzippingData:rawData];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:self.requestUrl]];
    [request setHTTPMethod:@"POST"];
    [request addValue:@"application/json;charset=UTF-8" forHTTPHeaderField:@"Content-Type"];
    [request addValue:@"gzip" forHTTPHeaderField:@"Content-Encoding"];
    [request setHTTPBody:gzippingData];
    return request;
}

YTKNetwork源码解析2

YTKUrlFilterProtocol 接口

YTKBatchRequest

疑问

YTKChainRequest

加载缓存的请求

定制 buildCustomUrlRequest

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