Question

我理解prepareForSegue函数，但我不确定如何设置一个可以接收实例的空变量。

swift 4 / Xcode 9.2

// I want to be able to send classes that look like this to var pickedQuiz

class mathQuestionBank {

var list = [Questions]()

init() {

    let item = Questions(text: "What is two plus two?", correctAnswer: "four", textA: "three", textB: "four", textC: "five", textD: "9y" )

    list.append(item)

    list.append(Questions(text: "How many sides does a triangle have?", correctAnswer: "three", textA: "two", textB: "four", textC: "three", textD: "five"))

    list.append(Questions(text: etc....

    }
}

class QuestionsViewController: UIViewController {

var pickedQuiz = mathQuestionBank() 

// I want to send the entire instance of mathQuestionBank() to var
pickedQuiz. How do I setup the variable pickedQuiz to receive instances 
like mathQuestionBank() ? I'd think it needs to be empty so that it can 
receive the instance from the prepareForSegue() function. 

}

Answer 1

您只需使用prepareForSegue()，

即可

let valueToPass = "HelloWorld"
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if segue.identifier == "segueIdentifier" {
            if let nextVC = segue.destinationViewController as? NextViewController {
                nextVC.yourVariable = valueToPass
            }
        }
    }

在您的其他课程中，您可以按如下方式定义变量：

class NextViewController {

var yourVariable = ABCType()

}

Answer 2

“传递一个实例”并不清楚你的意思。你的意思是传递一些自定义对象的实例，而不仅仅是像字符串这样的值类型？只需将@ Madhur示例中的yourVariable更改为所需的类类型：

class ClassToPass {
  value1: String? 
  value2: Data?
  value3: Int
  init(value1: String?, value2: Data?, value3: Int?) {
    self.value1 = value1
    self.value2 = value2
    self.value3 = value3
  }
}

class myViewController: UIViewController {

  override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if segue.identifier == "segueIdentifier" {
            if let nextVC = segue.destinationViewController 
              as? NextViewController {
                let valueToPass = ClassToPass(value1: "A String", 
                                              value2: nil, 
                                              value3: 7)

                nextVC.yourVariable = valueToPass
            }
        }
  }
}

//And in the other view controller:
class NextViewController {
  var yourVariable: ClassToPass? = nil
}

如何设置一个可以从prepareForSegue接收实例的空变量？

2 个答案: