AFNetWorking源码见解

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###AFNetWorking源码见解

文件结构：

  1. AFHTTPRequestOperationManager用于生成和管理AFHTTPRequestOperation,

  2. AFHTTPRequestOperation继承于AFURLConnectionOperation,

  3. AFURLConnectionOperation继承于NSOperation

普通的网络请求：

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[[AFHTTPRequestOperationManager manager] GET:urlString parameters:parameters success:successBlock failure:failureBlock];

1.单例初始化manager，同时初始化

a.AFHTTPRequestSerializer(请求头里面有关客户端的信息)，

b.AFJSONResponseSerializer(返回数据接收和处理格式)，

c.AFSecurityPolicy(请求安全，https)，

d.AFNetworkReachabilityManager(网络状态，wifi，2g，3g)，

e.operationQueue队列；

2.创建request，

3.由request创建操作，加入队列

4.开始操作，利用一个NSURLConnection进行网络请求，delegate回调

5.完成后，操作调用completionBlock回调，在回调中由response和error判断成功失败

start方法
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[self performSelector:@selector(operationDidStart) onThread:[[self class] networkRequestThread] withObject:nil waitUntilDone:NO modes:[self.runLoopModes allObjects]];

单例生成的Thread,runloop里面只有一个NSRunLoopCommonModes

生成常驻线程
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+ (void)networkRequestThreadEntryPoint:(id)__unused object {
    @autoreleasepool {
        [[NSThread currentThread] setName:@"AFNetworking"];

        NSRunLoop *runLoop = [NSRunLoop currentRunLoop];
        [runLoop addPort:[NSMachPort port] forMode:NSDefaultRunLoopMode];
        [runLoop run];
    }
}

+ (NSThread *)networkRequestThread {
    static NSThread *_networkRequestThread = nil;
    static dispatch_once_t oncePredicate;
    dispatch_once(&oncePredicate, ^{
        _networkRequestThread = [[NSThread alloc] initWithTarget:self selector:@selector(networkRequestThreadEntryPoint:) object:nil];
        [_networkRequestThread start];
    });
    
    return _networkRequestThread;
}

使用runloop生成一个常驻的线程，所有的网络请求都使用这个线程

所有的connection都由这个runloop发起，回调也是它接收

把一个异步任务加入group,防止多线程不执行block
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dispatch_group_enter(group); 
[strongSelf performBlock:^(){ 
    block(); 
    dispatch_group_leave(group); 
}];
``` 

###### 回调代码
  • (void)setCompletionBlock:(void (^)(void))block {
    [self.lock lock];
    if (!block) {
    [super setCompletionBlock:nil];
    } else {
    __weak __typeof(self)weakSelf = self;
[super setCompletionBlock:^ {
    __strong __typeof(weakSelf)strongSelf = weakSelf;

#pragma clang diagnostic push

#pragma clang diagnostic ignored “-Wgnu”
dispatch_group_t group = strongSelf.completionGroup ?: url_request_operation_completion_group();
dispatch_queue_t queue = strongSelf.completionQueue ?: dispatch_get_main_queue();

#pragma clang diagnostic pop

        dispatch_group_async(group, queue, ^{
            block();
        });

        dispatch_group_notify(group, url_request_operation_completion_queue(), ^{
            [strongSelf setCompletionBlock:nil];
        });
    }];
}
[self.lock unlock];

}

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1. 成员变量的对外接口都加了NSRecursiveLock递归锁
2. __weak __typeof(self)weakSelf = self;防止循环引用__strong __typeof(weakSelf)strongSelf = weakSelf;强引用防止被释放后出错
3. dispatch_group_t group = strongSelf.completionGroup ?: url_request_operation_completion_group();单例生成，完成时候，在group和main线程里面执行，执行完后回收

######使用batchOfRequest访问多组网络请求

  • (NSArray )batchOfRequestOperations:(NSArray )operations
      progressBlock:(void (^)(NSUInteger numberOfFinishedOperations, NSUInteger totalNumberOfOperations))progressBlock
completionBlock:(void (^)(NSArray *operations))completionBlock
    `
使用setShouldExecuteAsBackgroundTaskWithExpirationHandler决定APP进入后台后是否继续发送接收请求