（18/30 轉來轉去的Segues-3）

• 第二個畫面（LightRedViewController.swift）
  服從此協定的類別需實做setColor方法：

protocol LightRedViewControllerDelegate {
    func setColor(colorType:String)
}

class服從的協定：

class LightRedViewController: UIViewController,UIPickerViewDataSource,UIPickerViewDelegate

//專門用來接受第一個畫面所傳資料的屬性
//Optional String不用初始化
var inforFromViewOne:String?

//新增屬性
//delegate的值為ViewController(第一個畫面）
var delegate:LightRedViewControllerDelegate?
//PickerView顯示的資料
let colorArray = ["red","green","blue"]

viewDidLoad：

//將第一個畫面傳來的inforFromViewOne設定給myLable顯示
myLabel.text = inforFromViewOne
//服從協定
myPickerView.dataSource = self
myPickerView.delegate = self

PickerView的設定：

//顯示橫列的數量
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }
    
//顯示直列的數量
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return colorArray.count
    }
    
//顯示的內容
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return colorArray[row]
    }

設置返回按鈕：

@IBAction func backtoView1(_ sender: UIButton) {
    let colorNumber = myPickerView.selectedRow(inComponent: 0)
    let color = colorArray[colorNumber]
    //將顏色字串當作參數呼叫delegate，執行setColor方法
    delegate?.setColor(colorType: color)
    navigationController?.popViewController(animated: true)
}

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