等到alamofire完成获取请求并创建对象 [英] Wait until alamofire is done getting request and making object

问题描述

我在等待创建一个对象时遇到问题，然后希望更新UI。如果我运行该函数，它将立即退出索引错误，因为当它存在时，它试图从第一个对象中获取一些文本...有人能帮助我吗？

I am having a problem with waiting until one object is made, then I wish to update my UI. If i run the function, it will instantly get the out of index error because its trying to get some text from the first object when it dosent exist yet... Anyone who could help me?

func getMovieData(activeGenreLink: String){

    //self.posterLoading.startAnimating()

        Alamofire.request(activeGenreLink).responseJSON { response in
            //print(response.request)  // original URL request
            //print(response.response) // HTTP URL response
            //print(response.data)     // server data
            //print(response.result)   // result of response serialization
            var test = 0
            self.movieArray = []


            if let json = response.result.value as? Dictionary<String,AnyObject> {
                if let movies = json["results"] as? [AnyObject]{
                    for movie in movies{
                        let movieObject: Movie = Movie()

                        let title = movie["title"] as? String
                        let releaseDate = movie["release_date"] as! String
                        let posterPath = movie["poster_path"] as! String
                        let overView = movie["overview"] as! String
                        let movieId = movie["id"] as! Int
                        let genre_ids = movie["genre_ids"] as! [AnyObject]

                        movieObject.title = title
                        movieObject.movieRelease = releaseDate
                        movieObject.posterPath = posterPath
                        movieObject.overView = overView
                        movieObject.movieId = movieId


                        for genre in genre_ids{//Genre ids, fix this
                            movieObject.movieGenre.append(genre as! Int)
                        }



                        self.movieArray.append(movieObject)


                    }//End of for each movie
                }

            }


    }//End of Json request



}//End of getmoviedata

推荐答案

使用完成块/结束符。

func getMovieData(activeGenreLink: String,completion : ()->()){

    //self.posterLoading.startAnimating()

        Alamofire.request(activeGenreLink).responseJSON { response in
            //print(response.request)  // original URL request
            //print(response.response) // HTTP URL response
            //print(response.data)     // server data
            //print(response.result)   // result of response serialization
            var test = 0
            self.movieArray = []


            if let json = response.result.value as? Dictionary<String,AnyObject> {
                if let movies = json["results"] as? [AnyObject]{
                    for movie in movies{
                        let movieObject: Movie = Movie()

                        let title = movie["title"] as? String
                        let releaseDate = movie["release_date"] as! String
                        let posterPath = movie["poster_path"] as! String
                        let overView = movie["overview"] as! String
                        let movieId = movie["id"] as! Int
                        let genre_ids = movie["genre_ids"] as! [AnyObject]

                        movieObject.title = title
                        movieObject.movieRelease = releaseDate
                        movieObject.posterPath = posterPath
                        movieObject.overView = overView
                        movieObject.movieId = movieId


                        for genre in genre_ids{//Genre ids, fix this
                            movieObject.movieGenre.append(genre as! Int)
                        }



                        self.movieArray.append(movieObject)


                    }//End of for each movie
                }

            }

           completion()
    }//End of Json request

}

最后调用此方法，

self.getMovieData(activeGenreLink: "your_link_here", completion: {
            //updateUI
})

为什么？

由于Alamofire responseJSON是异步调用。当您调用方法 getMovieData 时，显然它返回而无需等待responseJSON完成。您需要一个完成处理程序来通知VC，VC调用了 getMovieData 来通知其完成。

Because Alamofire responseJSON is an asynchronous call. When you call your method getMovieData obviously it returns without waiting for responseJSON to finish. You need a completion handler to inform the VC which called getMovieData to inform the completion of it.

由于Alamofire responseJSON块在主线程上触发，因此您可以直接在完成块中更新UI，而无需更改线程。

Because Alamofire responseJSON block is triggered on main thread, you can directly update the UI in the completion block without having to change the thread.

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