Alamofire http json request block ui

Question

我一直在创建一个从JSON脚本检索对象的函数。我选择使用Alamofire作为异步请求，而Swiftyjson则可以轻松解析。但是，我似乎遇到阻止UI的问题吗？当是异步请求时如何做到这一点？我需要在单独的线程上运行它还是可以解释？

基本上我是通过阻止UI的意思是它在以下功能完成之前没有在其他按钮上做出反应。

func getRecent() {

    var url = "http://URL/recent.php?lastid=(lastObjectIndex)&limit=(numberOfRecordsPerAPICall)"

    isApiCalling = true
    request(.GET, url, parameters: nil)
        .response { (request, response, data, error) in
            if error == nil {
        let data: AnyObject = data!
        let jsonArray = JSON(data: data as! NSData)
        if jsonArray.count < self.numberOfRecordsPerAPICall {
            self.recentCount = 0
            self.tableVIew.tableFooterView = nil
        } else {
            self.recentCount = jsonArray.count
            self.tableVIew.tableFooterView = self.footerView
        }
        for (key: String, subJson: JSON) in jsonArray {
            // Create an object and parse your JSON one by one to append it to your array
            var httpUrl = subJson["image_url"].stringValue
            let url = NSURL(string: httpUrl)
            let data = NSData(contentsOfURL: url!)
            if UIImage(data: data!) != nil {
            // Create an object and parse your JSON one by one to append it to your array
            var newNewsObject = News(id: subJson["id"].intValue, title: subJson["title"].stringValue, link: subJson["url"].stringValue, imageLink: UIImage(data: data!)!, summary: subJson["news_text"].stringValue, date: self.getDate(subJson["date"].stringValue))



            self.recentArray.append(newNewsObject)
            }
        }
        self.lastObjectIndex = self.lastObjectIndex + self.numberOfRecordsPerAPICall
        self.isApiCalling = false
        self.tableVIew.reloadData()
        self.refreshControl?.endRefreshing()
        }
        }
}

Answer 1

响应闭合在主线程上执行。如果您在那里进行JSON解析（并且有大量数据）将阻止主线程一段时间。

在这种情况下，您应该使用dispatch_async进行JSON解析，并且仅在完成主线程时才使用。

只需像这样的解析

func getRecent() {
var url = "http://URL/recent.php?lastid=(lastObjectIndex)&limit=(numberOfRecordsPerAPICall)"

isApiCalling = true
request(.GET, url, parameters: nil)
    .response { (request, response, data, error) in
        if error == nil {
    let priority = DISPATCH_QUEUE_PRIORITY_DEFAULT
    dispatch_async(dispatch_get_global_queue(priority, 0)) {
        // Parse stuff here
        let data: AnyObject = data!
        let jsonArray = JSON(data: data as! NSData)
        if jsonArray.count < self.numberOfRecordsPerAPICall {
            self.recentCount = 0
            self.tableVIew.tableFooterView = nil
        } else {
            self.recentCount = jsonArray.count
            self.tableVIew.tableFooterView = self.footerView
        }
        for (key: String, subJson: JSON) in jsonArray {
            // Create an object and parse your JSON one by one to append it to your array
            var httpUrl = subJson["image_url"].stringValue
            let url = NSURL(string: httpUrl)
            let data = NSData(contentsOfURL: url!)
            if UIImage(data: data!) != nil {
            // Create an object and parse your JSON one by one to append it to your array
            var newNewsObject = News(id: subJson["id"].intValue, title: subJson["title"].stringValue, link: subJson["url"].stringValue, imageLink: UIImage(data: data!)!, summary: subJson["news_text"].stringValue, date: self.getDate(subJson["date"].stringValue))
            self.recentArray.append(newNewsObject)
            }
        }
        dispatch_async(dispatch_get_main_queue()) {
            // Update your UI here
            self.lastObjectIndex = self.lastObjectIndex + self.numberOfRecordsPerAPICall
            self.isApiCalling = false
            self.tableVIew.reloadData()
            self.refreshControl?.endRefreshing()
        }
    }
    }
    }
}

Answer 2

swift5 对Stefan Salatic回答的更新，如果您要从Alamofire响应中解析大量JSON数据，则最好使用全局调度队列，并且出于任何原因，您需要在主线程开关中更新UI到Dispatchque.main.main.main.ASYNC。

因此，示例代码看起来像这样。

AF.request(UrlGetLayers, method: .post, parameters: parameters, headers: headers)
            .responseJSON { response in
             DispatchQueue.global(qos: .background).async {
                
                //parse your json response here
                
                //oops... we need to update the main thread again after parsing json
                DispatchQueue.main.async {
                    
                }
                
             }
        }