objective-c - 递归-flattenMap : with Reactive Cocoa + OctoKit (fetching dynamic object graph from web service)

Question

我正在尝试使用 Octokit 预取 Github 存储库中文件的对象图这取决于 Reactive Cococa .我遇到了一个问题，它创建了一个信号，该信号将递归地向下钻取，直到没有更多的目录要获取为止。这是 repository of mine 的示例目录图(注意:文件已被省略，以保持图表简单明了)。

- (RACSignal *)fetchContentTreeForRepository:(OCTRepository *)repository {
    return [[self fetchContent:Nil forRepository:repository parentContent:nil] doCompleted:^{
        // fetching tree finished, persist in database
    }];
}

- (RACSignal *)fetchContent:(OCTContent *)content forRepository:(OCTRepository *)repository parentContent:(OCTContent *)parentContent {
    return [[[[self.client fetchContents:content forRepository:repository] collect] deliverOn:RACScheduler.mainThreadScheduler]
            flattenMap:^RACSignal *(NSArray *fetchedContents) {
                // set the contents that were fetched
                id<OCTContentStoreProtocol>store = content ?: repository;
                store.contents = fetchedContents;

                // only search for contents of type "dir" (directory)
                NSArray *directories = [fetchedContents filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"contentType = \"dir\""]];
                NSMutableArray *signals;
                for (OCTContent *fetchedDir in directories) {
                    [signals addObject:[self fetchContent:fetchedDir forRepository:repository parentContent:content]];
                }
                return [RACSignal merge:signals];
            }];
}

请注意:-fetchContents:forRepository: 构建一个请求路径并返回一个 RACSignal 将 HTTP 请求操作排队(它试图遵循语义 OctoKit does ).

我目前遇到的问题是此设置仅执行存储库内容的提取(即图中的顶级对象)。 -flattenMap: 被调用，信号数组被适本地创建，并且 -merge: 被返回。目的是创建一个递归链，当没有更多的目录类型子级时结束(可能应该添加一个 -filter: 来检查)。

目的是获取 Github 存储库的整个文件图，并在操作完成时收到通知。这是我想如何处理调用的示例:

[[[GHDataStore sharedStore] fetchContentTreeForRepository:self.repository]
 subscribeNext:^(NSArray *contents) {
     // this would be called each time a new set of contents is received
     NSLog(@"received %i contents",[contents count]);
 }
 error:^(NSError *error) {
     NSLog(@"error fetching: %@",error.localizedDescription);
 }
 completed:^{
     // this would be called when mapping the graph is finished
     NSLog(@"finished fetching contents");
 }];

知道为什么它只执行顶层吗？我原以为在 -fetchContentTreeForRepository: 上调用 -subscribeNext: 会执行 -flattenMap: 的返回信号，但看来我误会了什么。这个假设来自 chaining example在 Reactive Cocoa 自述文件中。

编辑:I am dumb.

Answer 1

问题是您从未初始化信号的 NSMutableArray:

NSMutableArray *signals;
for (OCTContent *fetchedDir in directories) {
       [signals addObject:[self fetchContent:fetchedDir forRepository:repository parentContent:content]];
}
return [RACSignal merge:signals];

将第一行更改为 NSMutableArray *signals = [NSMutableArray new] 它似乎可以工作。