How can font size control be implemented in MVVM on iOS?

1 year ago
Emily Johnson
2 minutes

In iOS, we can utilize the MVVM pattern to control the font size. One way to implement this is as follows:

  1. Firstly, establish a ViewModel class to handle the font-related logic. Within the ViewModel, an attribute can be defined to indicate the font size, for example:
class ViewModel {
    var fontSize: CGFloat = 16.0

    // 根据字号大小计算其他相关的字体属性，例如行间距、字间距等
    var lineSpacing: CGFloat {
        return fontSize * 0.5
    }

    // 其他相关的方法...
}
  1. In the View, adjust the font size of the Label using the font size from the ViewModel. For example:
class ViewController: UIViewController {
    @IBOutlet weak var label: UILabel!

    var viewModel = ViewModel()

    override func viewDidLoad() {
        super.viewDidLoad()

        // 设置Label的字体大小
        label.font = UIFont.systemFont(ofSize: viewModel.fontSize)

        // 设置Label的行间距
        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.lineSpacing = viewModel.lineSpacing
        let attributedString = NSAttributedString(string: label.text ?? "", attributes: [NSAttributedString.Key.paragraphStyle: paragraphStyle])
        label.attributedText = attributedString
    }

    // 其他相关的方法...
}
  1. In the Controller, the font size can be changed through user interaction. For example, a button can be added to click and change the font size.
@IBAction func increaseFontSize() {
    viewModel.fontSize += 2.0

    // 更新Label的字体大小
    label.font = UIFont.systemFont(ofSize: viewModel.fontSize)

    // 更新Label的行间距
    let paragraphStyle = NSMutableParagraphStyle()
    paragraphStyle.lineSpacing = viewModel.lineSpacing
    let attributedString = NSAttributedString(string: label.text ?? "", attributes: [NSAttributedString.Key.paragraphStyle: paragraphStyle])
    label.attributedText = attributedString
}

By following the steps above, you can use the MVVM pattern to control font size. Save the font size state in the ViewModel, let the View retrieve the font size through the ViewModel, and update the corresponding UI.

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