swift - 从类型 '(NSData!, NSError!) throws -> ()' 的抛出函数到非抛出函数类型 '(NSData!, NSError!) -> Void' 的转换无效

Question

我试图在 if let jsonData Array = try NSJSONSerialization... 行中从 Swift 1 转换为 2，因为它最初给了我一个来自“额外参数‘错误’的错误” call”所以我在 NSJSONSerialization 之前添加了“try”，但现在它说“从 '(NSData!, NSError!) throws -> ()' 类型的抛出函数到非抛出函数类型 '(NSData! , NSError!) -> Void'。我认为错误没有得到正确处理，但我不知道该怎么做。这是代码

httpHelper.sendRequest(httpRequest, completion: {(data:NSData!, error:NSError!) in
        if error != nil {
            let errorMessage = self.httpHelper.getErrorMessage(error)
            let errorAlert = UIAlertView(title:"Error", message:errorMessage as String, delegate:nil, cancelButtonTitle:"Ok")
            errorAlert.show()

            return
        }

        var error: NSError?

        // let jsonDataDict = try? NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions(0), error: &error) as! NSDictionary
        //  let jsonDataDict = try? NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions(rawValue: 0)) as! NSDictionary

        if let jsonDataArray = try NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions(rawValue: 0)) as? NSArray! {
            //load collection view with selfies
            if jsonDataArray != nil {
                for imageDataDict in jsonDataArray {
                    var selfieImgObj = SelfieImage()

                    selfieImgObj.imageTitle = imageDataDict.valueForKey("title") as! String
                    selfieImgObj.imageId = imageDataDict.valueForKey("random_id") as! String
                    selfieImgObj.imageThumbnailURL = imageDataDict.valueForKey("image_url") as! String

                    self.dataArray.append(selfieImgObj)
                }

                self.collectionView?.reloadData()
            }
        }
      })
    }

Answer 1

首先，您应该将所有调用 throws 的函数包装在 do-try-catch 循环中。其次，安全地将 jsonArray 解包为 Swift 数组，而不是尝试将其强制转换为 NSArray:

do {
    if let jsonArray = try NSJSONSerialization.JSONObjectWithData(NSData(), options: .AllowFragments) as? [AnyObject] {
        // unarchived data is an array
    }
} catch {
    print(error)
}