swift – 如何从NSURLSession.sharedSession()获取数据dataTaskWithRequest

概述class PostFOrData { let url = NSURL( string: "http://210.61.209.194:8088/SmarttvWebServiceTopmsoApi/GetReadlist") var picUrl = NSURL(string : "http://210.61.209.194:8088/SmarttvMedia/img/epi00

class PostFOrData {    let url = NSURL( string: "http://210.61.209.194:8088/SmarttvWebServicetopmsoAPI/GetReadList")    var picUrl = NSURL(string : "http://210.61.209.194:8088/SmarttvMedia/img/epi00001.png")    var responseString : Nsstring = ""    func forData() -> Nsstring {        let request = NSMutableURLRequest( URL: url!)        request.httpMethod = "POST"        var s : Nsstring = ""        let poststring : String = "uID=59"        request.httpBody = poststring.dataUsingEnCoding(NSUTF8StringEnCoding)        let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {            data,response,error in            if error != nil {                println("error=\(error)")                return            } else {                println("response = \(response!)")                self.responseString = Nsstring(data: data,enCoding: NSUTF8StringEnCoding)!                println("responseString = \(self.responseString)")            }        }        // I want to return Nsstring here,but I always get nothing        return self.responseString    }}

任何人都知道如何从任务获取数据？

您不能直接从异步任务返回数据.

Swift 2的解决方案是完成一个完成处理程序：

class PostFOrData {    // the completion closure signature is (Nsstring) -> ()    func forData(completion: (Nsstring) -> ()) {        if let url = NSURL(string: "http://210.61.209.194:8088/SmarttvWebServicetopmsoAPI/GetReadList") {            let request = NSMutableURLRequest( URL: url)            request.httpMethod = "POST"            let poststring : String = "uID=59"            request.httpBody = poststring.dataUsingEnCoding(NSUTF8StringEnCoding)            let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {                data,error in                if let data = data,JsonString = Nsstring(data: data,enCoding: NSUTF8StringEnCoding)                    where error == nil {                        completion(JsonString)                } else {                    print("error=\(error!.localizedDescription)")                }            }            task.resume()        }    }}let pfd = PostFOrData()// you call the method with a trailing closurepfd.forData { JsonString in    // and here you get the "returned" value from the asynchronous task    print(JsonString)}

这样,只有当异步任务完成时才调用完成.这是一种“返回”数据而不实际使用返回的方式.

Swift 3版本

class PostFOrData {    // the completion closure signature is (String) -> ()    func forData(completion:  @escaPing (String) -> ()) {        if let url = URL(string: "http://210.61.209.194:8088/SmarttvWebServicetopmsoAPI/GetReadList") {            var request = URLRequest(url: url)            request.httpMethod = "POST"            let poststring : String = "uID=59"            request.httpBody = poststring.data(using: String.EnCoding.utf8)            let task = URLSession.shared.dataTask(with: request) {                data,let JsonString = String(data: data,enCoding: String.EnCoding.utf8),error == nil {                    completion(JsonString)                } else {                    print("error=\(error!.localizedDescription)")                }            }            task.resume()        }    }}let pfd = PostFOrData()// you call the method with a trailing closurepfd.forData { JsonString in    // and here you get the "returned" value from the asynchronous task    print(JsonString)}

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