Objective C: 有没有办法在另一个方法中调用一个方法的完成块？

Question

我有多个 GET API 请求方法在完成时调用完成块。这是一个例子。

- (void)getUserInfo
    onSuccess:(void (^)(id))successBlock
    onFailure:(void (^)(NSError *))failureBlock {

    NSString *urlStr = [NSString stringWithFormat:@"%@/user/", baseUrl];

    [manager GET:urlStr parameters:nil progress:nil
          success:^(NSURLSessionTask *task, id responseObject) {
              successBlock(responseObject);
          }
          failure:^(NSURLSessionTask *operation, NSError *error) {
              failureBlock(error);
          }];
}

但是，我注意到我在其他方法中重复了管理器 GET 请求代码。我想创建另一种方法来处理所有请求并删除重复代码。 URL 似乎是唯一改变的东西。但是，有一个缺陷。我需要调用 successBlock 让方法知道请求已经完成。

也许我需要完全走另一条路，做一些不同的事情。

Answer 1

您可以传递完成块，然后从处理所有 get 请求的最终方法中调用它们。为了简洁起见，我通常会制作将要重用的 typedef 的完成块。这是我的意思的一个例子（我添加了第二个示例方法，它也传递到中心 getRequestWithURLString:onSuccess:onFailure: 方法）：

LLFakeManager.h

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

typedef void (^_Nullable SuccessCompletionBlock)(id responseObject);
typedef void (^_Nullable FailureCompletionBlock)(NSError *error);

@interface LLFakeManager : NSObject
- (void)getUserInfoOnSuccess:(SuccessCompletionBlock)successBlock onFailure:(FailureCompletionBlock)failureBlock;
- (void)getBooksCheckedOutOnSuccess:(SuccessCompletionBlock)successBlock onFailure:(FailureCompletionBlock)failureBlock;
@end

NS_ASSUME_NONNULL_END

LLFakeManager.m

#import "LLFakeManager.h"

@interface LLFakeManager()
- (void)getRequestWithURLString:(NSString *)urlString
                      onSuccess:(SuccessCompletionBlock)successBlock
                      onFailure:(FailureCompletionBlock)failureBlock;
@end

@implementation LLFakeManager

- (void)getUserInfoOnSuccess:(SuccessCompletionBlock)successBlock onFailure:(FailureCompletionBlock)failureBlock {
    NSString *urlStr = @"FakeUserUrlPath";
    [self getRequestWithURLString:urlStr onSuccess:successBlock onFailure:failureBlock];
}

- (void)getBooksCheckedOutOnSuccess:(SuccessCompletionBlock)successBlock onFailure:(FailureCompletionBlock)failureBlock {
    NSString *urlString = @"FakeBooksUrlPath";
    [self getRequestWithURLString:urlString onSuccess:successBlock onFailure:failureBlock];
}

// central method that will handle all the get requests
- (void)getRequestWithURLString:(NSString *)urlString
                      onSuccess:(SuccessCompletionBlock)successBlock
                      onFailure:(FailureCompletionBlock)failureBlock {
    // some fake implementation here to do your request, then use the completion block passed in from whatever other method
    if (successBlock) {
        successBlock(@"responseObjectPassedBackHere");
    }
}

@end

以及调用它的示例：

LLFakeManager *manager = [[LLFakeManager alloc] init];
[manager getUserInfoOnSuccess:^(id  _Nonnull responseObject) {
    NSLog(@"Here's my response object = %@", responseObject);
} onFailure:^(NSError * _Nonnull error) {
    // no implementation but same idea
}];

会产生这个日志：

Here's my response object = responseObjectPassedBackHere

此站点：http://goshdarnblocksyntax.com 是一个方便的块语法列表，可能对您也有帮助。

Answer 2

这些块——如果它们具有相同的签名——它们可以沿着一系列方法传递。您的 GET 块带有一个不必要的第一个参数。 NSURLSessionTask *，如果要 returned，应该同步 returned。将其移出区块签名将使您能够标准化区块。

用代码说比较容易...

// changed this method name so it would compile

- (void)getUserInfoOnSuccess:(void (^)(id))successBlock
                   onFailure:(void (^)(NSError *))failureBlock {

    NSString *urlStr = [NSString stringWithFormat:@"%@/user/", baseUrl];

   // two things: get the task as a return value (if you need it)
   // pass the blocks directly, without nesting them in new blocks
    NSURLSessionTask *task = [manager GET: urlStr
                               parameters: nil
                                 progress: nil
                                  success: successBlock
                                  failure: failureBlock];
    // do something with the task
}

要完成这项工作，请更改 GET 方法 return 类型并阻止签名...

- (NSURLSessionTask *)GET:(NSString *)url parameters:(id)params progress:(id)progress success:(void (^)(id))successBlock failure:(void (^)(NSError *))failureBlock {
    // return the session task created here
    return task
}

Objective C: 有没有办法在另一个方法中调用一个方法的完成块？

Objective C: Is there a way to call a completion block for a method in another method?

ios

objective-c

objective-c-blocks

completionhandler

LLFakeManager.h

LLFakeManager.m