ios - 不调用 responseJSON 的 Alamofire completionHandler

Question

我有以下代码来获取对评论列表的回复。 (1条评论多条回复)

static func fetchCommentsAndTheirReplies(articleId: String, failure: (()->Void)?, success: (comments: [[String: AnyObject]], replies: [[[String: AnyObject]]], userIds: Set<String>)->Void) {
    var retComments = [[String: AnyObject]]()
    var retReplies = [[[String: AnyObject]]]()
    var retUserIds = Set<String>()

    Alamofire.request(.GET, API.listComment, parameters: [API.articleId: articleId]).responseJSON {
        response in
        guard let comments = response.result.value as? [[String: AnyObject]] else {
            failure?()
            return
        }
        print(comments)
        retComments = comments

        let group = dispatch_group_create()

        for (commentIndex, comment) in comments.enumerate() {
            guard let id = comment["_id"] as? String else {continue}

            let relevantUserIds = parseRelaventUserIdsFromEntity(comment)
            for userId in relevantUserIds {
                retUserIds.insert(userId)
            }

            retReplies.append([[String: AnyObject]]())

            dispatch_group_enter(group)
            Alamofire.request(.GET, API.listReply, parameters: [API.commentId: id]).responseJSON {
                response in
                if let replies = response.result.value as? [[String: AnyObject]] {
                    for (_, reply) in replies.enumerate() {

                        let relevantUserIds = parseRelaventUserIdsFromEntity(reply)
                        for userId in relevantUserIds {
                            retUserIds.insert(userId)
                        }
                    }
                    //TODO: need to capture commentIndex?
                    retReplies[commentIndex] = replies
                }
                dispatch_group_leave(group)
            }


        }

        dispatch_group_wait(group, DISPATCH_TIME_FOREVER)
        success(comments: retComments, replies: retReplies, userIds: retUserIds)
    }
}

API.listReply 请求的完整处理程序永远不会被调用。 dispatch_group_enter(group) 被调用一次，dispatch_group_leave(group) 永远不会被调用。代码卡在 dispatch_group_wait。奇怪的是，连UI都卡住了，这很奇怪，因为整个功能都是异步的。

Answer 1

我遇到过类似的问题:

在主 UI 线程上，调用:

dispatch_semaphore_wait(loginDoneSemaphore, DISPATCH_TIME_FOREVER)

并使用 Alamofire 调用 http，内部也使用您的 httpRequest.responseJSON

-> 终于在 responseJSON 完成处理程序中找到了从未调用过的代码

-> 导致在 DISPATCH_TIME_FOREVER 之后查找代码从未被调用

-> 最终找到根本原因是:Alamofire 的responseJSON，默认情况下，如果不传入线程/队列，将在Main UI 线程上运行

-> 在调用 Alamofire 之前，在主 UI 线程中使用 DISPATCH_TIME_FOREVER 锁定 UI 线程

-> 所以在 Alamofire 的 responseJSON 之后，它也在主 UI 线程上运行，永远不会调用

-> 我的解决方案是:指定 Alamofire 在另一个线程上做 http 响应:

let BackgroundThread:dispatch_queue_t = dispatch_get_global_queue(QOS_CLASS_BACKGROUND, 0)

func dispatchBackground_async(thingsTodo:()->()) {
    dispatch_async(BackgroundThread, thingsTodo)
}

dispatchBackground_async({
    httpRequest.responseJSON(queue: BackgroundThread, completionHandler: { response in
        gLog.debug("request=\(response.request), response=\(response.response), statusCode=\(response.response?.statusCode), result=\(response.result)")
        // [Debug] [com.apple.root.background-qos] [CrifanLibHttp.swift:21]
})

这可能对你引用有用。

->也许你可以用我的方法:为Alamofire的responseJSON设置另一个线程，来解决你的问题。