YTKChainRequest

的 理解key

 源码 注释， 很清楚。

///  The success callback. Note if this value is not nil and `requestFinished` delegate method is

///  also implemented, both will be executed but delegate method is first called. This block

///  will be called on the main queue.

@property (nonatomic, copy, nullable) YTKRequestCompletionBlock successCompletionBlock;

///  The failure callback. Note if this value is not nil and `requestFailed` delegate method is

///  also implemented, both will be executed but delegate method is first called. This block

///  will be called on the main queue.

@property (nonatomic, copy, nullable) YTKRequestCompletionBlock failureCompletionBlock;

block 的 优化

- (void)loginButtonPressed:(id)sender {

    RegisterApi *api = [[RegisterApi  alloc ]  init];       

 [api  startWithCompletionBlockWithSuccess:  ^(YTKBaseRequest  *  request) {

//你可以直接在这里使用 self

NSLog(@"succeed");        

}

failure:^(YTKBaseRequest *request) {

//你可以直接在这里使用 self

NSLog(@"failed");      

  }]; 

   }}

注意：你可以直接在 block 回调中使用self，不用担心循环引用。因为 YTKRequest 会在执行完 block 回调之后，将相应的 block 设置成 nil。从而打破循环引用。

源码： 

@implementation YTKRequest

- (void)start {

if (self.ignoreCache) {

[self startWithoutCache];

return;}

// Do not cache download request.

if (self.resumableDownloadPath) {

[self startWithoutCache];

return;}

if (![self loadCacheWithError:nil]) {

[self startWithoutCache];

return;}

_dataFromCache = YES;

dispatch_async(dispatch_get_main_queue(), ^{

[self requestCompletePreprocessor];

[self requestCompleteFilter];

YTKRequest *strongSelf = self;

[strongSelf.delegate requestFinished:strongSelf];

if (strongSelf.successCompletionBlock) {

strongSelf.successCompletionBlock(strongSelf);}

[strongSelf clearCompletionBlock];  // nil out to break the retain cycle.

});

}

- (void)clearCompletionBlock {

// nil out to break the retain cycle.

self.successCompletionBlock = nil;

self.failureCompletionBlock = nil;

}

校验，支持检查返回 JSON 内容的合法性

 使用了Key-Value Validation, 我觉得