ios - 为什么我不能通过 preparetosegue 方法传递我在 ViewDidAppear/ViewDidLoad 中定义的任何计算和变量？我怎样才能做到这一点？

Question

没错，正如标题。我开始将我的 HTTP 请求 session 放在 viewdidload 中，直到我意识到这是一个糟糕的地方，因为它在调用的方法层次结构中太低了，而且基本上没有希望在那里定义变量以传递给另一个 VC。

然而，我切换到 Viewdidappear，但当我通过 prepareforsegue 传递变量时，我仍然得到 nil。我可以使用另一种方法吗，或者您建议我如何实现我想要的？每当我按下按钮时，我都可以发布请求，这肯定会传递变量吗？

override func viewDidLoad() {
    super.viewDidLoad()
    activityIndicatorView.startAnimating()
}

override func viewDidAppear(animated: Bool) {

    super.viewDidAppear(animated)

    let request = NSMutableURLRequest(URL: NSURL(string: "http://127.0.0.1:5000")!)
    request.HTTPMethod = "POST"
    let postString = "color=\(self.finalDataPassed)&location=\(self.thirdDataPassed)&weather=\(self.dataPassed)&city=\(self.secondDataPassed)"

    request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
    let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
        data, response, error in

        if error != nil {
            println("error=\(error)")
            return
        }

        println("response = \(response)")

        let responseString = NSString(data: data, encoding: NSUTF8StringEncoding)

        println(responseString)
        var error: NSError?

        let result = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: &error) as? NSDictionary

        var dict: NSDictionary = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as! NSDictionary


        if(error != nil) {
            println(error!.localizedDescription)
            let jsonStr = NSString(data: data, encoding: NSUTF8StringEncoding)
            println("Error could not parse JSON: '\(jsonStr)'")
        }
        else {
            if let results = result?.valueForKey("result") as? NSArray {
                dispatch_async(dispatch_get_main_queue(), {
                    println(results)
                })
            }

            let parseJSON: AnyObject? = result!.valueForKey("result")
            var stuff: AnyObject! = parseJSON!.valueForKey("price")
            var otherstuff: NSString! = parseJSON!.valueForKey("YlowestURL") as! NSString
        }

        self.activityIndicatorView.stopAnimating()
    self.performSegueWithIdentifier("calculateToDisplaySegue", sender: nil)
    }
    task.resume()

}
override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

var stuff: String!
var otherstuff: String!


override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if (segue.identifier == "calculateToDisplaySegue"){

        var svc = segue.destinationViewController as! PriceViewController;
        svc.dataPassed = self.stuff
        svc.secondDataPassed = self.otherstuff

    }
}

Answer 1

stuff 和 otherstuff 是在方法本地定义的，而不是在类实例变量中。

IOW 使用:

self.stuff = parseJSON!.valueForKey("price")
self.otherstuff = parseJSON!.valueForKey("YlowestURL") as! NSString

当然 stuff 和 otherstuff 必须声明为适当类型的 ivars 来代替:

var stuff: String!
var otherstuff: String!