将NSData转换为NSString始终返回nil

Question

我遇到一个问题，我无法成功将NSData转换为NSString

我使用google drive sdks使用

获取我的Google文档内容

var fetcher:GTMHTTPFetcher = service.fetcherService.fetcherWithURLString(downloadurl as! String)

fetcher.beginFetchWithCompletionHandler({(olddata:NSData!, error:NSError!) in
        if(error == nil) {
        print(olddata)
}

else {
        print("error is \(error)")
     }
})

olddata是NSData（没有可选）
我想转换为NSString

但使用基本转换时总是返回nil

let myStringFromData = NSString(data: olddata, encoding: NSUTF8StringEncoding)

我该如何解决这个问题

Answer 1

string

或

import Foundation

let string = "what i would like to send to server as utf8 text"
var utf8text = string.utf8.map { $0 }
utf8text.append(0)
let data = NSData(bytes: &utf8text, length: utf8text.count)

// ..... upload, download, data is now received NSData from server

let p = UnsafePointer<Int8>(data.bytes)
if let received = String.fromCString(p) {

    print(received) // what i would like to send to server as utf8 text

}else {
    print("error by reconstructing string from data")
}

或

let string = "what i would like to send to server as utf8 text"
var buffer = string.nulTerminatedUTF8.map{ $0 }
let data = NSData(bytes: &buffer, length: buffer.count)

// ..... upload, download, data is now received NSData from server

let p = UnsafePointer<Int8>(data.bytes)
if let received = String.fromCString(p) {

    print(received) // what i would like to send to server as utf8 text

}else {
    print("error by reconstructing string from data")
}