本文介绍了如何从 NSURLSession.sharedSession().dataTaskWithRequest 获取数据的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
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/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
}
}
有人知道如何从任务中获取数据吗?
Anyone know how to get the data from task?
推荐答案
不能直接从异步任务返回数据.
You can't return data directly from an asynchronous task.
Swift 2 的解决方案是创建一个像这样的完成处理程序:
The solution with Swift 2 is to make a completion handler like this:
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, response, 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 closure
pfd.forData { jsonString in
// and here you get the "returned" value from the asynchronous task
print(jsonString)
}
这样,只有在异步任务完成时才会调用completion.这是一种无需实际使用 return
即可返回"数据的方法.
That way, the completion is only called when the asynchronous task is completed. It is a way to "return" the data without actually using return
.
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, response, error in
if let data = 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 closure
pfd.forData { jsonString in
// and here you get the "returned" value from the asynchronous task
print(jsonString)
}
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