AFNetworking源码探究（九） —— AFURLSessionManagerTaskDelegate

原创

conanma

修改于 2021-09-03 17:58:03

5120

修改于 2021-09-03 17:58:03

文章被收录于专栏：正则正则

回顾

上面一篇，主要讲述了代理NSURLSessionDownloadDelegate中的三个方法，这一篇我们就看一下AFN自定义代理AFURLSessionManagerTaskDelegate中三个代理转发的实现。

1. - (void)URLSession:(__unused NSURLSession )session task:(NSURLSessionTask )task didCompleteWithError:(NSError *)error

先看一下该自定义代理方法的实现。

- (void)URLSession:(__unused NSURLSession *)session
              task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error
{
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wgnu"
    __strong AFURLSessionManager *manager = self.manager;

    __block id responseObject = nil;

    __block NSMutableDictionary *userInfo = [NSMutableDictionary dictionary];
    userInfo[AFNetworkingTaskDidCompleteResponseSerializerKey] = manager.responseSerializer;

    //Performance Improvement from #2672
    NSData *data = nil;
    if (self.mutableData) {
        data = [self.mutableData copy];
        //We no longer need the reference, so nil it out to gain back some memory.
        self.mutableData = nil;
    }

    if (self.downloadFileURL) {
        userInfo[AFNetworkingTaskDidCompleteAssetPathKey] = self.downloadFileURL;
    } else if (data) {
        userInfo[AFNetworkingTaskDidCompleteResponseDataKey] = data;
    }

    if (error) {
        userInfo[AFNetworkingTaskDidCompleteErrorKey] = error;

        dispatch_group_async(manager.completionGroup ?: url_session_manager_completion_group(), manager.completionQueue ?: dispatch_get_main_queue(), ^{
            if (self.completionHandler) {
                self.completionHandler(task.response, responseObject, error);
            }

            dispatch_async(dispatch_get_main_queue(), ^{
                [[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingTaskDidCompleteNotification object:task userInfo:userInfo];
            });
        });
    } else {
        dispatch_async(url_session_manager_processing_queue(), ^{
            NSError *serializationError = nil;
            responseObject = [manager.responseSerializer responseObjectForResponse:task.response data:data error:&serializationError];

            if (self.downloadFileURL) {
                responseObject = self.downloadFileURL;
            }

            if (responseObject) {
                userInfo[AFNetworkingTaskDidCompleteSerializedResponseKey] = responseObject;
            }

            if (serializationError) {
                userInfo[AFNetworkingTaskDidCompleteErrorKey] = serializationError;
            }

            dispatch_group_async(manager.completionGroup ?: url_session_manager_completion_group(), manager.completionQueue ?: dispatch_get_main_queue(), ^{
                if (self.completionHandler) {
                    self.completionHandler(task.response, responseObject, serializationError);
                }

                dispatch_async(dispatch_get_main_queue(), ^{
                    [[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingTaskDidCompleteNotification object:task userInfo:userInfo];
                });
            });
        });
    }
#pragma clang diagnostic pop
}

这里有几点需要注意：

(a) userInfo参数

这个参数是一个可变字典。

NSString * const AFNetworkingTaskDidCompleteResponseSerializerKey = @"com.alamofire.networking.task.complete.responseserializer";

__block NSMutableDictionary *userInfo = [NSMutableDictionary dictionary];
userInfo[AFNetworkingTaskDidCompleteResponseSerializerKey] = manager.responseSerializer;

这个userInfo用来存储一些相关信息，存储responseSerializer响应解析对象。

(b) 释放mutableData内存

这一段代码需要我们学习。

//Performance Improvement from #2672
NSData *data = nil;
if (self.mutableData) {
    data = [self.mutableData copy];
    //We no longer need the reference, so nil it out to gain back some memory.
    self.mutableData = nil;
}

当我们不用self.mutableData这个对象的时候，就设置为nil，节省内存，数据通过data传出去了。

(c) 有错误error不为空

if (error) {
    userInfo[AFNetworkingTaskDidCompleteErrorKey] = error;

    dispatch_group_async(manager.completionGroup ?: url_session_manager_completion_group(), manager.completionQueue ?: dispatch_get_main_queue(), ^{
        if (self.completionHandler) {
            self.completionHandler(task.response, responseObject, error);
        }

        dispatch_async(dispatch_get_main_queue(), ^{
            [[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingTaskDidCompleteNotification object:task userInfo:userInfo];
        });
    });
}

有错误的话，就按照上面的逻辑进行处理。

首先就是更新userInfo信息

NSString * const AFNetworkingTaskDidCompleteErrorKey = @"com.alamofire.networking.task.complete.error";

userInfo[AFNetworkingTaskDidCompleteErrorKey] = error;

然后就是在主线程进行block回调，并发出了一个通知AFNetworkingTaskDidCompleteNotification。

dispatch_group_async(manager.completionGroup ?: url_session_manager_completion_group(), manager.completionQueue ?: dispatch_get_main_queue(), ^{
    if (self.completionHandler) {
        self.completionHandler(task.response, responseObject, error);
    }

    dispatch_async(dispatch_get_main_queue(), ^{
        [[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingTaskDidCompleteNotification object:task userInfo:userInfo];
    });
});

(d) 无错误

 else {
    dispatch_async(url_session_manager_processing_queue(), ^{
        NSError *serializationError = nil;
        responseObject = [manager.responseSerializer responseObjectForResponse:task.response data:data error:&serializationError];

        if (self.downloadFileURL) {
            responseObject = self.downloadFileURL;
        }

        if (responseObject) {
            userInfo[AFNetworkingTaskDidCompleteSerializedResponseKey] = responseObject;
        }

        if (serializationError) {
            userInfo[AFNetworkingTaskDidCompleteErrorKey] = serializationError;
        }

        dispatch_group_async(manager.completionGroup ?: url_session_manager_completion_group(), manager.completionQueue ?: dispatch_get_main_queue(), ^{
            if (self.completionHandler) {
                self.completionHandler(task.response, responseObject, serializationError);
            }

            dispatch_async(dispatch_get_main_queue(), ^{
                [[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingTaskDidCompleteNotification object:task userInfo:userInfo];
            });
        });
    });
}

上面就是无错误时的处理工作：

首先我们注意下队列，是在一个并行队列执行的。

static dispatch_queue_t url_session_manager_processing_queue() {
    static dispatch_queue_t af_url_session_manager_processing_queue;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        af_url_session_manager_processing_queue = dispatch_queue_create("com.alamofire.networking.session.manager.processing", DISPATCH_QUEUE_CONCURRENT);
    });

    return af_url_session_manager_processing_queue;
}

无错误时候的处理，都是在这个队列中进行处理的。

解析数据

NSError *serializationError = nil;
responseObject = [manager.responseSerializer responseObjectForResponse:task.response data:data error:&serializationError];

- (id)responseObjectForResponse:(NSURLResponse *)response
                           data:(NSData *)data
                          error:(NSError *__autoreleasing *)error
{
    [self validateResponse:(NSHTTPURLResponse *)response data:data error:error];

    return data;
}

- (BOOL)validateResponse:(NSHTTPURLResponse *)response
                    data:(NSData *)data
                   error:(NSError * __autoreleasing *)error
{
    BOOL responseIsValid = YES;
    NSError *validationError = nil;

    if (response && [response isKindOfClass:[NSHTTPURLResponse class]]) {
        if (self.acceptableContentTypes && ![self.acceptableContentTypes containsObject:[response MIMEType]] &&
            !([response MIMEType] == nil && [data length] == 0)) {

            if ([data length] > 0 && [response URL]) {
                NSMutableDictionary *mutableUserInfo = [@{
                                                          NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: unacceptable content-type: %@", @"AFNetworking", nil), [response MIMEType]],
                                                          NSURLErrorFailingURLErrorKey:[response URL],
                                                          AFNetworkingOperationFailingURLResponseErrorKey: response,
                                                        } mutableCopy];
                if (data) {
                    mutableUserInfo[AFNetworkingOperationFailingURLResponseDataErrorKey] = data;
                }

                validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorCannotDecodeContentData userInfo:mutableUserInfo], validationError);
            }

            responseIsValid = NO;
        }

        if (self.acceptableStatusCodes && ![self.acceptableStatusCodes containsIndex:(NSUInteger)response.statusCode] && [response URL]) {
            NSMutableDictionary *mutableUserInfo = [@{
                                               NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: %@ (%ld)", @"AFNetworking", nil), [NSHTTPURLResponse localizedStringForStatusCode:response.statusCode], (long)response.statusCode],
                                               NSURLErrorFailingURLErrorKey:[response URL],
                                               AFNetworkingOperationFailingURLResponseErrorKey: response,
                                       } mutableCopy];

            if (data) {
                mutableUserInfo[AFNetworkingOperationFailingURLResponseDataErrorKey] = data;
            }

            validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorBadServerResponse userInfo:mutableUserInfo], validationError);

            responseIsValid = NO;
        }
    }

    if (error && !responseIsValid) {
        *error = validationError;
    }

    return responseIsValid;
}

大家看一下，这里还验证了response的有效性，具体怎么验证后面会分篇进行说明。

如果是下载文件，那么responseObject为下载的路径

if (self.downloadFileURL) {
    responseObject = self.downloadFileURL;
}

写入userInfo

if (responseObject) {
    userInfo[AFNetworkingTaskDidCompleteSerializedResponseKey] = responseObject;
}

如果解析response有错误，就更新userInfo

if (serializationError) {
    userInfo[AFNetworkingTaskDidCompleteErrorKey] = serializationError;
}

结果的回调

dispatch_group_async(manager.completionGroup ?: url_session_manager_completion_group(), manager.completionQueue ?: dispatch_get_main_queue(), ^{
    if (self.completionHandler) {
        self.completionHandler(task.response, responseObject, serializationError);
    }

    dispatch_async(dispatch_get_main_queue(), ^{
        [[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingTaskDidCompleteNotification object:task userInfo:userInfo];
    });
});

在下面的队列组中进行完成的处理

static dispatch_group_t url_session_manager_completion_group() {
    static dispatch_group_t af_url_session_manager_completion_group;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        af_url_session_manager_completion_group = dispatch_group_create();
    });

    return af_url_session_manager_completion_group;
}

这里其实就结果的回调self.completionHandler(task.response, responseObject, serializationError)，并发出通知，name为NSString * const AFNetworkingTaskDidCompleteNotification = @"com.alamofire.networking.task.complete";。

2. - (void)URLSession:(unused NSURLSession )session dataTask:(unused NSURLSessionDataTask )dataTask didReceiveData:(NSData *)data

- (void)URLSession:(__unused NSURLSession *)session
          dataTask:(__unused NSURLSessionDataTask *)dataTask
    didReceiveData:(NSData *)data
{
    [self.mutableData appendData:data];
}

这个很好理解，其实就是周期性的调用，在这个方法里面拼接了数据。

3. - (void)URLSession:(NSURLSession )session downloadTask:(NSURLSessionDownloadTask )downloadTask didFinishDownloadingToURL:(NSURL *)location

下载成功了被NSURLSession代理转发到这里

- (void)URLSession:(NSURLSession *)session
      downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location
{
    NSError *fileManagerError = nil;
    self.downloadFileURL = nil;

    if (self.downloadTaskDidFinishDownloading) {
        self.downloadFileURL = self.downloadTaskDidFinishDownloading(session, downloadTask, location);
        if (self.downloadFileURL) {
            [[NSFileManager defaultManager] moveItemAtURL:location toURL:self.downloadFileURL error:&fileManagerError];

            if (fileManagerError) {
                [[NSNotificationCenter defaultCenter] postNotificationName:AFURLSessionDownloadTaskDidFailToMoveFileNotification object:downloadTask userInfo:fileManagerError.userInfo];
            }
        }
    }
}

这个大家是否注意到以前那个转发到这里的NSURLSession的代理方法，里面也有关于路径的处理，这里也进行了处理，两处都处理了，为什么呢？

转发前的NSURLSession代理的下载路径是所有request公用的下载路径，一旦设置，所有的request都会下载到之前那个路径。而这个是对应的每个task的，每个task可以设置各自下载路径。

后记

本篇解析的就是AFURLSessionManagerTaskDelegate代理中实现的三个方法。喜欢的点个赞~~~

原创声明：本文系作者授权腾讯云开发者社区发表，未经许可，不得转载。

如有侵权，请联系 cloudcommunity@tencent.com 删除。

ios

原创声明：本文系作者授权腾讯云开发者社区发表，未经许可，不得转载。

如有侵权，请联系 cloudcommunity@tencent.com 删除。

ios

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