Question

我有以下代码：

var resultData:NSData?

task = session!.dataTaskWithRequest(request) { (data: NSData!, response: NSURLResponse!, error: NSError!) in

    if ((error) != nil) {
        println("Error")
        return
    }
    resultData = data
}

task!.resume()

但是，执行后resultData为nil。如何获取请求返回的数据？

Answer 1

检查您的数据是否为零，然后您可以使用

这是一个Swift 3示例：

let url = NSURL(string: "https://itunes.apple.com/search?term=jack+johnson&limit=2")!
let request = NSMutableURLRequest(url: url as URL)
let session = URLSession.shared

let task = session.dataTask(with: request as URLRequest) { data, response, error in
    if error != nil {
        print("error: \(error!.localizedDescription): \(String(describing: error))")
    }
    else if data != nil {
        if let str = NSString(data: data!, encoding: String.Encoding.utf8.rawValue) {
            print("Received data:\n\(str)")
        }
        else {
            print("unable to convert data to text")
        }
    }

}
task.resume()

Answer 2

dataTask将执行该函数是一个异步，如果要使用它必须在数据任务函数内使用的结果数据。现在print语句将打印响应。如果在dataTask func之外使用resultData，它将返回nil

var resultData:NSData?

let dataTask = session.dataTask(with: request as URLRequest) {
            (data, response, error) in

            guard let data = data, error == nil else { return }

            if error != nil {
                error
}
resultData = data
print(NSString(data: data, encoding: String.Encoding.utf8.rawValue)!)
}dataTask.resume()

NSURLSession dataTaskWithRequest Swift

2 个答案: