RGB調色盤：view + slider * 3 + textfield * 3

昨天介紹了每個物件的功能！
今天主要講解：

1. TextFieldDelegate 如何寫出 textField 的輸入限制
2. @IBAction 與 storyboard 的拉線

除了講解程式碼之外，還會附上截圖以供參考。

1. 在 Class 函數外，寫 extension ViewController : UITextFieldDelegate（裡面寫判斷字串長度的函數）

extension ViewController : UITextFieldDelegate {
    //新的字串可判斷字串長度，決定是否可以輸入。回傳 true 允許文字輸入，回傳 false 讓文字不能輸入。
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
       var result = false
       if let text = textField.text, let range = Range(range, in: text) {
           let newText = text.replacingCharacters(in: range, with: string)
           // 判斷只能輸入3位數
           if newText.count < 4 {
              result = true
           }
       }
       return result
    }
}

2. 在 storyboard 拉線到對應的 @IBAction
   textField：
   

   slider：
   

   delegate：
   

附上RGB調色盤完整程式碼

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var showcolor: UIView!
    @IBOutlet weak var redtext: UITextField!
    @IBOutlet weak var greentext: UITextField!
    @IBOutlet weak var bluetext: UITextField!
    @IBOutlet weak var redslider: UISlider!
    @IBOutlet weak var greenslider: UISlider!
    @IBOutlet weak var blueslider: UISlider!
    
    override func viewDidLoad() {
        super.viewDidLoad()

        let tap: UITapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(dismissKeyBoard))
        self.view.addGestureRecognizer(tap)
    }

    @objc func dismissKeyBoard() {
        self.view.endEditing(true)
    }
 
    @IBAction func TextFieldToSilder(textField: UITextField) {
        guard let stringColor = textField.text else {return}
        guard let intColor = Int(stringColor)else {return}
        switch textField {
        case redtext:
            redslider.setValue(Float(intColor), animated: true)
        case greentext:
            greenslider.setValue(Float(intColor), animated: true)
        case bluetext:
            blueslider.setValue(Float(intColor), animated: true)
        default: break
        }
    }

    @IBAction func SliderToTextField(_ sender: Any) {
        redtext.text = "\(Int(redslider.value))"
        greentext.text = "\(Int(greenslider.value))"
        bluetext.text = "\(Int(blueslider.value))"
    }

    @IBAction func colorchange(_ sender: Any){
        showcolor.backgroundColor = UIColor(red: CGFloat(redslider.value)/255, green: CGFloat(greenslider.value)/255, blue: CGFloat(blueslider.value)/255, alpha: 1)
    }
}

extension ViewController : UITextFieldDelegate {
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
       var result = false
       if let text = textField.text, let range = Range(range, in: text) {
           let newText = text.replacingCharacters(in: range, with: string)
           if newText.count < 4 {
              result = true
           }
       }
       return result
    }
}

明天會介紹關於 storyboard 的 layout(約束)拉法，敬請期待！