没有用于选择器rac_sendAsynchronousRequest的已知类mehtod

Question

我知道这听起来很明显，但我收到了以下错误：No known class mehtod for selector rac_sendAsynchronousRequest

排成一行：

return [[[NSURLConnection rac_sendAsynchronousRequest]

整个方法体是：

+(RACSignal*)download:(NSString*)urlString{

    NSAssert(urlString, @"URL must not be nil");

    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:urlString]];

    return [[[NSURLConnection rac_sendAsynchronousRequest]
              map:^id(RACTuple *value) {

                  return [value second];
              }]

            deliverOn:[RACScheduler mainThreadScheduler]];

}

在我的标题中，我确实导入了类别和库标题：

#import<ReactiveCocoa/ReactiveCocoa.h>
#import <ReactiveCocoa/NSURLConnection+RACSupport.h>

在NSURLConnection+RACSupport.h我可以看到方法声明：

@class RACSignal;

@interface NSURLConnection (RACSupport)

// Lazily loads data for the given request in the background.
//
// request - The URL request to load. This must not be nil.
//
// Returns a signal which will begin loading the request upon each subscription,
// then send a `RACTuple` of the received `NSURLResponse` and downloaded
// `NSData`, and complete on a background thread. If any errors occur, the
// returned signal will error out.
+ (RACSignal *)rac_sendAsynchronousRequest:(NSURLRequest *)request;

@end

为什么XCode没有看到这种方法？

Answer 1

您的代码中缺少request参数：

 return [[[NSURLConnection rac_sendAsynchronousRequest:request]
              map:^id(RACTuple *value) {

                  return [value second];
              }]

            deliverOn:[RACScheduler mainThreadScheduler]];