Question

我需要在另一个请求中执行HTTP请求，据我所知，这需要同步在这种情况下，我获取一系列“帖子”并获取有关它们的信息这是代码，以帮助您更好地了解情况：

// getPosts()
...
let task = NSURLSession.sharedSession().dataTaskWithRequest(request, completionHandler: { (data: NSData!, response: NSURLResponse?, error: NSError?) -> Void in
    if response != nil {
        let dataDictionary = NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers, error: &err) as [NSDictionary]     
        for postDic: NSDictionary in dataDictionary {
           let post = Post(postId: postDic["post_id"] as String)

           post.likes = postDic["likes"] as String
           post.views = postDic["views"] as String

           self.getCommentCountForPostID(post.postId, completion: { (count) -> Void in
               post.comments = count
           })

           ...
           self.posts.addObject(post)
        }
        // reloading table view etc
    }
})
task.resume()

这是函数getCommentCountForPostID：

func getCommentCountForPostID(postID: String, completion: ((count : String?) -> ())) {
    ...
    let task = NSURLSession.sharedSession().dataTaskWithRequest(request, completionHandler: { (data: NSData!, response: NSURLResponse?, error: NSError?) -> Void in
        if response != nil {
            let resultCount: NSString! = NSString(bytes: data.bytes, length: data.length, encoding: NSASCIIStringEncoding)
            print(resultCount)

            completion(count: resultCount)
        }

    })

    task.resume()
}

问题是getCommentCountForPostID函数在for循环向前运行时异步调度。我需要该函数首先评论请求完成，然后继续执行getPosts()。我尝试了许多使用dispatch_sync()在代码中包装不同部分的组合，但没有成功我怎样才能做到这一点？非常感谢！

Answer 1

为您的目的使用递归。

加载第一篇文章 - ＆gt;处理它 - ＆gt;加载下一个 - ＆gt;加载所有帖子后完成。

我创建了一个名为'loopAndLoad'的辅助方法，它将您的数据数组作为参数，并处理当前项的索引

let task = NSURLSession.sharedSession().dataTaskWithRequest(request, completionHandler: { (data: NSData!, response: NSURLResponse?, error: NSError?) -> Void in
            if response != nil {
                let dataDictionary = NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers, error: &err) as [NSDictionary]
                self.loopAndLoad(0, dataDictionary);
            }
        })
        task.resume()



    func loopAndLoad( index: Int, dataArray: Array<NSDictionary>)
    {
        let postDic = dataArray[index]
        let post = Post(postId: postDic["post_id"] as String)

        post.likes = postDic["likes"] as String
        post.views = postDic["views"] as String

        self.getCommentCountForPostID(post.postId, completion: { (count) -> Void in
            post.comments = count
            self.posts.addObject(post)
            if (++index < dataArray.count)
            {
                self.loopAndLoad(index, dataArray)
            }
            else
            {
                /// end of loop
            }
        })
    }


    func getCommentCountForPostID(postID: String, completion: ((count : String?) -> ())) {
        ...
        let task = NSURLSession.sharedSession().dataTaskWithRequest(request, completionHandler: { (data: NSData!, response: NSURLResponse?, error: NSError?) -> Void in
            if response != nil {
                let resultCount: NSString! = NSString(bytes: data.bytes, length: data.length, encoding: NSASCIIStringEncoding)
                print(resultCount)

                completion(count: resultCount)
            }

        })

        task.resume()
    }

iOS中另一个请求中的HTTP请求

1 个答案: