iOS AFNetworiking源码解读一

请求实现

AFNetworiking是基于苹果网络框架的封装,要了解AFNetworiking的实现,
我们先来看看怎么自己实现一次简单的网络请求,先熟悉一下流程.
如下代码:

- (void)requestPost
{
    
    //1.请求参数
    NSDictionary *dicParam = @{@"key":@"value"};
    NSError *error = nil;
    NSData *bodyData = [NSJSONSerialization dataWithJSONObject:dicParam options:0 error:&error];
    if (error) {
        return;
    }
    
    NSString *baseUrl = @"https://xxx.com";// 请求 url
    
    //2.create request
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:baseUrl]];
    [request setValue:[NSString stringWithFormat:@"%ld", (long) [bodyData length]] forHTTPHeaderField:@"Content-Length"];
    [request setHTTPMethod:@"POST"];//请求类型配置
    [request setValue:@"application/json; charset=UTF-8" forHTTPHeaderField:@"Content-Type"];
    [request setValue:@"gzip" forHTTPHeaderField:@"Accept-Encoding"];
    [request setHTTPBody:bodyData];
    
    //3.create Configuration
    NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
    configuration.timeoutIntervalForRequest = 15.0;
    
    //4.发起请求,这里选用delegate的方式接收返回结果
    NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];
    NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request];
    [dataTask resume];
    
}

遵循NSURLSessionDataDelegate协议,实现协议方法,接收回调

//5.接收回调数据
#pragma mark - NSURLSessionDataTaskDelegate
-(void)URLSession:(NSURLSession *)session dataTask:(nonnull NSURLSessionDataTask *)dataTask didReceiveData:(nonnull NSData *)data
{
    NSLog(@"这个就是请求返回数据:%@",data);
}

由上面代码可看出,一次简单的网络请求,简单分为5步:

1.配置请求参数,请求URL;
2.创建request,并设置request的参数;
3.创建NSURLSessionConfiguration,并配置参数;
4.发起请求(此处为delegate方式);
5.接收回调,处理请求结果,请求完成.

由于iOS9后不支持NSURLConnection,第4步发起请求我们使用的是NSURLSession
AF内请求类型有:GET,HEAD,POST,PUT,DELETE.

AFNetworking的网路请求实现

AF实现网路请求两个核心类

AFHTTPSessionManager,AFURLSessionManager.(其中AFHTTPSessionManager 继承自AFURLSessionManager)

@interface AFHTTPSessionManager : AFURLSessionManager <NSSecureCoding, NSCopying>

其中AFHTTPSessionManager类我们可以理解为管理request和sessionConfiguration的类,对应上面1,2,3步
AFURLSessionManage为管理发起和接收请求的类,对应上面的4,5步

具体实现

此处我们以AF的POST方法实现举例,以下只挑关键的方法说明;
使用AF的POST请求,我们首先要创建AFHTTPSessionManager对象,调用AFHTTPSessionManager的实例方法POST:

AF的POST请求

创建AFHTTPSessionManager对象,
有没有上面2,3步的感觉?

- (AFHTTPSessionManager *)sessionManager
{
    if (_sessionManager == nil) {
        
        _sessionManager = [AFHTTPSessionManager manager];//manager 也是每次都创建
        //返回数据自动解析 当前没有解析 返回的是二进制
        [_sessionManager setResponseSerializer:[AFHTTPResponseSerializer serializer]];
        //设置responseSerializer的值
        [_sessionManager.responseSerializer setAcceptableContentTypes:[NSSet setWithObjects:@"application/json", @"text/json", @"text/javascript",@"text/html",@"text/plain",@"image/png", nil]];//类似第二步的request设置
        [_sessionManager.requestSerializer setTimeoutInterval:15.0];//类似第三步的SessionConfiguration设置

    }
    return _sessionManager;
}

上面是通过通过类方法manager创建的对象,对应下图,可以看到此时NSURLSessionConfiguration为nil

创建AFHTTPSessionManager对象

接着调用POST方法,看我添加的注释,先创建了request,接着调用请求方法

- (NSURLSessionDataTask *)dataTaskWithHTTPMethod:(NSString *)method
                                       URLString:(NSString *)URLString
                                      parameters:(id)parameters
                                         success:(void (^)(NSURLSessionDataTask *, id))success
                                         failure:(void (^)(NSURLSessionDataTask *, NSError *))failure
{
    NSError *serializationError = nil;
    //注意,此处返回了request,下面需要用到改request
    NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:method URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:&serializationError];
    if (serializationError) {
        if (failure) {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wgnu"
            dispatch_async(self.completionQueue ?: dispatch_get_main_queue(), ^{
                failure(nil, serializationError);
            });
#pragma clang diagnostic pop
        }

        return nil;
    }

    __block NSURLSessionDataTask *dataTask = nil;
    //调用父类AFURLSessionManager的方法,通过上面的request发起请求
    dataTask = [self dataTaskWithRequest:request completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
        if (error) {
            if (failure) {
                failure(dataTask, error);
            }
        } else {
            if (success) {
                success(dataTask, responseObject);
            }
        }
    }];

    return dataTask;
}

请求方法内部实现,在自己的队列内同步发起请求,然后设置代理,此方法为AFURLSessionManager的方法

- (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request
                            completionHandler:(void (^)(NSURLResponse *response, id responseObject, NSError *error))completionHandler
{
    __block NSURLSessionDataTask *dataTask = nil;
    //以下对应咱们说的第4步,发起请求,设置delegate
    //在自己的队列内执行同步方法
    dispatch_sync(url_session_manager_creation_queue(), ^{
        //发起请求
        dataTask = [self.session dataTaskWithRequest:request];
    });
    //设置delegate
    [self addDelegateForDataTask:dataTask completionHandler:completionHandler];

    return dataTask;
}

代理方法实现,接收数据

#pragma mark - NSURLSessionDataTaskDelegate
//回调内接收数据,对应第5步
- (void)URLSession:(__unused NSURLSession *)session
          dataTask:(__unused NSURLSessionDataTask *)dataTask
    didReceiveData:(NSData *)data
{
    [self.mutableData appendData:data];
}

到此,整个AFNetworking的POST请求流程大致过程结束,get到的朋友点下❤️
AF网络请求的其他细节请听下回分解.