问题
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
回答1:
Use completion block/closure.
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
}
Finally call this method,
self.getMovieData(activeGenreLink: "your_link_here", completion: {
//updateUI
})
Why?
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.
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.
来源：https://stackoverflow.com/questions/43204249/wait-until-alamofire-is-done-getting-request-and-making-object