在圖像上使用未解析的標識符

Question

我最近開始從官方 Apple Developer 網站學習 IOS 開發。 現在我在嘗試用作按鈕圖像的 3 張圖像上出現此錯誤。 我得到的錯誤是我試圖在變量中轉換的 3 個圖像。

@IBInspectable var starSize: CGSize = CGSize(width: 44.0, height: 44.0) {
    didSet {
        setupButtons()
    }
}

@IBInspectable var starCount: Int = 5 {
    didSet {
        setupButtons()
    }
}

//MARK: Intialization
override init(frame: CGRect) {
    super.init(frame: frame)
    setupButtons()
}

required init(coder: NSCoder) {
    super.init(coder: coder)
    setupButtons()
}

//MARK: Button Action
@objc func ratingButtonTapped(button: UIButton) {

}

//MARK: Private Methods
private func setupButtons() {
    for button in ratingButtons {
        removeArrangedSubview(button)
        button.removeFromSuperview()
    }
    ratingButtons.removeAll()

    let filledStar_ = UIImage(named: filledStar)
    let emptyStar_ = UIImage(named: emptyStar)
    let highlightedStar_ = UIImage(named: highlightedStar)

    for _ in 0..<starCount  {
        let button = UIButton()
        button.setImage(emptyStar_, for: .normal)
        button.setImage(filledStar_, for: .selected)
        button.setImage(highlightedStar_, for: .highlighted)
        button.setImage(highlightedStar_, for: [.highlighted, .selected])
        button.translatesAutoresizingMaskIntoConstraints = false
        button.heightAnchor.constraint(equalToConstant: starSize.height).isActive = true
        button.widthAnchor.constraint(equalToConstant: starSize.width).isActive = true
        button.addTarget(self, action: #selector(RatingControl.ratingButtonTapped(button:)), for: .touchUpInside)
        addArrangedSubview(button)
        ratingButtons.append(button)
    }
}

Answer 1

圖像名稱應該是一個字符串

let filledStar_ = UIImage(named: "filledStar")
let emptyStar_ = UIImage(named: "emptyStar")
let highlightedStar_ = UIImage(named: "highlightedStar")

Answer 2

我認為圖像文字也可能有效。