arrays - FOR IN 循环出错

Question

我正在尝试在 for in 循环中为数组 quandlURLs 运行以下函数。我在“loadDataFromURL”行中收到错误，提示:无法将 [String] 类型的值转换为“Sting”类型的预期参数。有人可以告诉我我在这里缺少什么吗？谢谢!!

class func getDataFromQuandlWithSuccess(success: ((Quandl: NSData!) -> Void)) {
 let quandlGold = "https://www.quandl.com/api/v3/datasets/LBMA/GOLD.json?auth_token=xyzDP7Cj-2F_Jss7sYHf&rows=1"        
quandlURLs = [quandlGold, quandlSilver,quandlPlatinum,quandlPalladium]
    var index: Int
    var urlData = [String]()
    for index in quandlURLs {
        loadDataFromURL(NSURL(string: quandlURLs[index])!, completion:{(data, error) -> Void in
            //2
            if let urlData[index] = data {
                //3
                success(Quandl: urlData[index])
                //below worked and showed raw data
                //print("Successful \(urlData)")

            }
        })

    }
}

这是 loadDataFromURL 函数

class func loadDataFromURL(url: NSURL, completion:(data: NSData?, error: NSError?) -> Void) {
let session = NSURLSession.sharedSession()

// Use NSURLSession to get data from an NSURL
let loadDataTask = session.dataTaskWithURL(url, completionHandler: { (data: NSData?, response: NSURLResponse?, error: NSError?) -> Void in
  if let responseError = error {
    completion(data: nil, error: responseError)
  } else if let httpResponse = response as? NSHTTPURLResponse {
    if httpResponse.statusCode != 200 {
      let statusError = NSError(domain:"com.raywenderlich", code:httpResponse.statusCode, userInfo:[NSLocalizedDescriptionKey : "HTTP status code has unexpected value."])
      completion(data: nil, error: statusError)
    } else {
      completion(data: data, error: nil)
    }
  }
})

loadDataTask.resume()
}
}

Answer 1

您需要在这里做的就是更改 for index in quandlURLs至for index in 0..<quandlURLs.count

if let urlData[index] = data 也存在问题，因为不能对数组使用可选绑定(bind)，所以需要定义一个新值，所以转到 if let urlDataEntry = data ，在这种情况下，您的 urlIndex 数组应该是 NSData 类型。

您也不需要 var index: Int线。在创建 Int 数组的 ..< 函数上使用 for in 循环时，会推断出 Int，并且索引变量在整个 for 循环中都可用。

例如:

class func getDataFromQuandlWithSuccess(success: ((Quandl: NSData!) -> Void)) {
    let quandlGold = "https://www.quandl.com/api/v3/datasets/LBMA/GOLD.json?auth_token=xyzDP7Cj-2F_Jss7sYHf&rows=1"        
    quandlURLs = [quandlGold, quandlSilver,quandlPlatinum,quandlPalladium]
    var urlData = [NSData]()
    for index in 0..<quandlURLs.count {
        loadDataFromURL(NSURL(string: quandlURLs[index])!, completion:{(data, error) -> Void in
            //2
            if let urlDataEntry = data {
                //3
                urlData[index] = urlDataEntry
                success(Quandl: urlDataEntry)
                //below worked and showed raw data
                //print("Successful \(urlData)")

            }
         })

    }
}