RACSignal：RACSignal 代码未执行

Question

有没有好心人可以帮我解决这个问题？

这是我的场景：

我需要将表单附件上传到服务器。所以这里是步骤：

使用 Web 服务从服务器检索附件 header。
将附件 header 与本地附件匹配。
上传附件到服务器。

问题：

使用 RACSignal 我可以成功获取附件 headers 但是当使用 NSArray 上传附件时，UploadFormItemAttachments 方法的内部 RACSignal 将不会执行。

附加信息：

这是显示如何处理 RACSignals 的代码片段。 BatchSignal 永远不会执行！：

[[[self getFormItemAttachmentHeaders:listName
                          topListItemID:form.topListItemID
                                  form:form
     ] map:^id(NSMutableArray* value) {
        NSArray* attachmentHeaders = [value copy];

        // the code of uploadFormItemAttachments is called but the inner signal does not execute. Why?
        return [self uploadFormItemAttachments:pendingAttachments
                                        attachmentHeaders:attachmentHeaders
                                                     form:form];
        }
      ] subscribeNext:^(id value) {
          // I was expecting the completion result form uploadFormItemAttachments here.
        }
     ];

这是遍历附件数组并将其上传到服务器的方法：

- (RACSignal *)uploadFormItemAttachments:(NSArray*)pendingAttachments attachmentHeaders:(NSArray*)attachmentHeaders form:(SEFSManagedForm*)form
{

  RACSignal* batchSignal = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    [attachmentHeaders enumerateObjectsUsingBlock:^(SEFSFormItemAttachmentHeader* attachmentHeader, NSUInteger idx, BOOL *stop)
     {
       // Look for the local attachment using attachment header from server

       NSPredicate* predicate = [NSPredicate predicateWithFormat:@"identifier = %@", attachmentHeader.document];
       NSArray* foundAttachment = [pendingAttachments filteredArrayUsingPredicate:predicate];

       SEFSManagedAttachment* fullAttachment = foundAttachment[0];

       RACSignal* uploadFormItemAttachmentSignal = [[self uploadFormItemAttachment:fullAttachment
                                                                  attachmentHeader:attachmentHeader                                                            ] map:^id(NSNumber* value) {
         NSMutableArray* valuesArray = [NSMutableArray array];
         [valuesArray addObject:value];
         [valuesArray addObject:attachmentHeader.document];
         RACTuple* tuple = [RACTuple tupleWithObjectsFromArray:valuesArray
                                            convertNullsToNils:YES];
         return tuple;
       }];


       [subscriber sendNext:uploadFormItemAttachmentSignal];
     }];

    [subscriber sendCompleted];
    return nil;
  }];

  return [batchSignal flatten:2];
}

Answer 1

因为 uploadFormItemAttachments returns RACSignal 你应该使用 flattenMap 而不是 map

RACSignal：RACSignal 代码未执行

RACSignal: RACSignal code is not executed

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