今天我們要介紹UIPickerView，UIPickerView可以讓你在列表中選擇所需要的項目，後面有一個練習會用到UIPickerView，就讓我們期待一下吧～現在先來簡單介紹如何使用UIPickerView！
首先我們在storyboard裡面新增UIPickerView以及等等用來顯示UIPickerView值的UILabel

接著宣告一筆資料用於在UIPickerView上顯示

let week = ["星期一","星期二","星期三","星期四","星期五","星期六","星期日"]

也要記得設定UIPickerView的delegate和dataSource

接著寫一個extension

extension ViewController: UIPickerViewDelegate, UIPickerViewDataSource {
    // UIPickerView 有幾列可以選擇
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }
    // UIPickerView 各列有多少行資料
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return week.count
    }
    // UIPickerView 每個選項顯示的資料
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return week[row]
    }
    // UIPickerView 改變選擇後執行的動作
    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        lbl.text = week[row]
    }

}

如此一來就完成了一個簡單的UIPickerView囉
執行結果如下