iOS Swift，返回到视图控制器的同一个实例

问题描述：

我遇到了问题，我有两个视图控制器A和B.视图控制器B有一个地图，上面有一个路线绘图。我此时可以在两个视图控制器之间前后移动，但每次加载时都会重置B视图控制器。我想这是因为我正在使用segues并且每次都在创建一个View控制器的新实例。

I have a problem, where I have two view controllers A and B. View controller B has a map, with a route draw on it. I can move back and forwards between the two view controllers at the moment, but the B view controller is reset every time it loads. I think this is because I am using segues and it is creating a new instance of a View controller every time.

我尝试使用以下代码来解决这个问题，但它仍然无法正常工作。视图加载正确，但视图控制器B仍在重置

I have tried using the following code to solve this issue, but it is still not working. The views load correctly, but view controller B is still being reset

@IBAction func mapButton(sender: AnyObject){
        let storyboard = UIStoryboard(name: "MainStoryboard", bundle: nil)
        let vc = storyboard.instantiateViewControllerWithIdentifier("SecondViewController") as! UIViewController
        self.presentViewController(vc, animated: true, completion: nil)
}

我做错了什么，我该如何解决？我希望视图控制器B与地图和路径一起保留在内存中，因此当用户返回时，他不必再次输入所有信息。

What am I doing wrong and how can I fix it? I want view controller B to stay in the memory along with the map and the route, so when a user returns he doesn't have to enter all of the information again.

答

您应该在UIViewController类型的类中创建一个变量，并将代码更改为以下内容：

You should create a variable in your class of type UIViewController and change your code to the following:

@IBAction func mapButton(sender: AnyObject){
    if yourVariable == nil {
        let storyboard = UIStoryboard(name: "MainStoryboard", bundle: nil)
        yourVariable = storyboard.instantiateViewControllerWithIdentifier("SecondViewController") as! UIViewController
    }
    self.presentViewController(yourVariable, animated: true, completion: nil)
}

这样你就可以创建一次viewController，保存它，如果你想再次打开它，就会显示之前创建的一个。

That way you create the viewController one time, save it and if you want to open it again present the previously created one.

iOS Swift，返回到视图控制器的同一个实例

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