ios - SWIFT 从另一个 Controller 访问数据

Question

这个问题已经有答案了:

How do you share data between view controllers and other objects in Swift? (9 个回答)

已关闭 7 年前。

例如，我有 2 个 Controller 已在内存中(Class 1、Class 2)。如何从 2 类访问 1 类数据？

class Class_1: UIViewController {

    var number:UInt8 = 1

    override func viewDidAppear(animated: Bool) {
        number = 8
    }   
}

如何访问 2 类中的数字变量并打印它的值？重点是不要创建新实例，重点是获取内存中 Class 1 的指针并访问它的数据。

Answer 1

首先将 ViewController 的名称从 Class_1 更改为 Class1ViewController，将 Class_2 更改为 Class2ViewController

您需要在Class1ViewController中初始化Class2ViewController时设置变量，并将数据从Class2ViewController传回给 Class1ViewController你需要使用委托(delegate)

要将Class1ViewController数据传输到Class2ViewController，请打开Class1ViewController文件并添加以下prepareForSegue方法(如果您使用 Storyboard)

class Class1ViewController: UIViewController{
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if segue.identifier == "Class2ViewController" {
            if let class2ViewController = segue.destinationViewController as? Class2ViewController {
                class2ViewController.inforFromClass1 = "Class 2 Variable set from Class 1"
            }
        }
    }
}

但是，如果您使用xib并且有一个从Class1ViewController移动到Class2ViewController的按钮，则应在触发Class2ViewController的按钮的IBAction中编写以下代码

class Class1ViewController: UIViewController{
    @IBAction showClass2ViewController(){
    let secondViewController = SecondViewController(nibName:"SecondViewController", bundle: NSBundle.mainBundle())
    secondViewController.infoFromClass1 = "Class 2 Variable set from Class 1"
    self.showViewController(secondViewController, sender: self)
   }
}

这是在 Class2ViewController 上设置变量，同时从 Class1ViewController 显示变量的方法

现在要将消息从 Class2ViewController 传递到 Class1ViewController，您需要使用委托(delegate)。打开Class2ViewController并在顶部添加以下协议(protocol)

@objc protocol Class2ViewContollerDelegate :class{
   func printMessageFromClass2ViewController()
}

class Class2ViewController: UIViewController {   
}

在 Class2ViewController 类中添加对 delagate 的弱引用，并在其 ViewDidAppear 或您喜欢的任何其他方法中调用它，

@objc protocol Class2ViewContollerDelegate :class{
   func printMessageFromClass2ViewController()
}

class Class2ViewController: UIViewController {
   weak var delegate: Class2ViewControllerDelegate?
   override func viewDidAppear(animated: Bool) {
        self.delegate?.printValueFromClass2ViewController
   }   
}

现在我们已经在Class2ViewController中定义了协议(protocol)，我们需要在Class1ViewController中实现它。返回在您的 Class1ViewController 文件中实现这样的协议(protocol)

class Class1ViewController: UIViewController, Class2ViewControllerDelegate {
    func printMessageFromClass2ViewController(){
        print("hey I just printed message in Class1ViewController through its delegate in Class2ViewController")
    }

    // For Xibs
    @IBAction showClass2ViewController(){
        let secondViewController = SecondViewController(nibName: "SecondViewController", bundle: NSBundle.mainBundle())
        secondViewController.infoFromClass1 = "Class 2 Variable set from Class 1"
        self.showViewController(secondViewController, sender: self)
    }

    //  For storyboards
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if segue.identifier == "Class2ViewController" {
            if let class2ViewController = segue.destinationViewController as?Class2ViewController {
                class2ViewController.inforFromClass1 = "Class 2 Variable set from Class 1"
            }
        }
    }
}