[英]SWIFT2.0: function returns before task is completed
我敢肯定,對大多數人來說這很容易,但是我是一個初學者,我無法弄清楚這一點。
我建立了一個在線解析JSON文件的功能。 解析完文件后,該函數應返回String,但是它不等待任務完成才返回。 因此,我總是以錯誤的值結尾。
我的功能:
func getJsonDataFromPath(path: String) -> String {
var videoId: String
videoId = "++ empty ++"
let url = NSURL(string:path)
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithURL(url!) { (data: NSData?, response: NSURLResponse?, error: NSError?) -> Void in
if let httpResponse = response as? NSHTTPURLResponse {
print("HTTP RESPONSE: \(httpResponse.statusCode)")
} // END OF if let httpResponse = response as? NSHTTPURLResponse
let json = JSON(data: data!)
// print(json)
if (json.count > 0) {
videoId = json[0]["videoId"].string!
print("videoId is: \(videoId)")
}
}
task.resume()
return videoId
}
及其調用:
override func viewDidLoad() {
super.viewDidLoad()
let test = getJsonDataFromPath("http://coulon.xyz/JobX/APIs/getListOfJobs.php")
print("Value returned by getJsonDataFromPath: \(test)")
}
我總是以錯誤的順序得到輸出:
getJsonDataFromPath返回的值:++空++ HTTP響應:200 videoId為:kzv1NQGdsyk
如何在返回值之前確保task.resume已完成?
在此先多謝
問候,朱利安
您應該像這樣實現Swift閉包:
func getJsonDataFromPath(path: String, completion: (item: String)-> Void){
var videoId: String
videoId = "++ empty ++"
let url = NSURL(string:path)
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithURL(url!) { (data: NSData?, response: NSURLResponse?, error: NSError?) -> Void in
if let httpResponse = response as? NSHTTPURLResponse {
print("HTTP RESPONSE: \(httpResponse.statusCode)")
} // END OF if let httpResponse = response as? NSHTTPURLResponse
let json = JSON(data: data!)
// print(json)
if (json.count > 0) {
videoId = json[0]["videoId"].string!
print("videoId is: \(videoId)")
completion(item: videoId)
}
}
task.resume()
}
及其調用:
override func viewDidLoad() {
super.viewDidLoad()
getJsonDataFromPath("http://coulon.xyz/JobX/APIs/getListOfJobs.php") { (test) -> Void in
print("Value returned by getJsonDataFromPath: \(test)")
}
}
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