Swift:使用未解析的标识符"json" [英] Swift : Use of unresolved identifier 'json'

问题描述

我目前正在使用Swift 2.0和Xcode 7.0.1开发我的第一个iOS应用.

I'm currently developing my first iOS app using Swift 2.0 and Xcode 7.0.1.

我遇到一个奇怪的小错误，似乎无法解决:

I'm getting a strange little error that I can't seem to fix:

        var err: NSError?

原始代码:

        //var json = NSJSONSerialization.JSONObjectWithData(data, options: .MutableContainers, error: &err) as? NSDictionary

Swift2重写代码:

Swift2 rewrite code:

        do {
            if let json = try NSJSONSerialization.JSONObjectWithData(data!, options: []) as? NSDictionary {
                print(json)
            }
        } catch {
            print(error)
        }

在重写之前使用未解析的标识符'json'

Use of unresolved identifier 'json' before rewriting

        if let parseJSON = json {
            var resultValue = parseJSON["status"] as? String
            print("result: \(resultValue)")

            var isUserRegistered:Bool = false;
            if(resultValue=="Success") { isUserRegistered = true; }

            var messageToDisplay:String = parseJSON["message"] as! String!;
            if(!isUserRegistered)
            {
                messageToDisplay = parseJSON["message"] as! String!;
            }

            dispatch_async(dispatch_get_main_queue(),{

                //Display alert message with confirmation.
                var myAlert = UIAlertController(title:"Alert", message:messageToDisplay, preferredStyle: UIAlertControllerStyle.Alert);

                let okAction = UIAlertAction(title:"Ok", style:UIAlertActionStyle.Default){ action in
                    self.dismissViewControllerAnimated(true, completion: nil);
                }

                myAlert.addAction(okAction);
                self.presentViewController(myAlert, animated:true, completion:nil);
            });  
        }

此行引发错误:

            if let parseJSON = json {

有人可以告诉我我在做什么错吗?

Can someone please tell me what I'm doing wrong here?

推荐答案

变量json仅在do块的范围内可见.

the variable json is visible only in the scope of the do block.

将代码移到do块中.
也不需要可选的绑定.如果代码通过try语句，则parseJSON有效且非可选.

Move the code into the do block.
Optional bindings is not needed, too. If the code passes the try statement, parseJSON is valid and non-optional.

do {
   let parseJSON = try NSJSONSerialization.JSONObjectWithData(data!, options: []) as! NSDictionary {
   print(parseJSON)
   var resultValue = parseJSON["status"] as? String
   print("result: \(resultValue)")

   var isUserRegistered:Bool = false;
   if(resultValue=="Success") { isUserRegistered = true; }

   var messageToDisplay:String = parseJSON["message"] as! String!;
   if(!isUserRegistered)
   {
      messageToDisplay = parseJSON["message"] as! String!;
   }

   dispatch_async(dispatch_get_main_queue(),{

      //Display alert message with confirmation.
      var myAlert = UIAlertController(title:"Alert", message:messageToDisplay, preferredStyle: UIAlertControllerStyle.Alert);

      let okAction = UIAlertAction(title:"Ok", style:UIAlertActionStyle.Default){ action in
          self.dismissViewControllerAnimated(true, completion: nil);
       }

       myAlert.addAction(okAction);
       self.presentViewController(myAlert, animated:true, completion:nil);
   });  

} catch let error as NSError {
    print(error)
}

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