如何通过单击按钮更改UIFont？

Question

我为笔记应用程序创建了一个UITextView。我想动态地单击KeyboardButton时更改UIFont。我尝试使用此代码，但它更改了UITextView中的所有文本。我想在按下按钮后更改字体。谁能帮我吗？

func setKeyboard() {

    let bar = UIToolbar()
    let flex = UIBarButtonItem(barButtonSystemItem: UIBarButtonItem.SystemItem.flexibleSpace, target: self, action: nil)
    let reset = UIBarButtonItem(image: UIImage(named: "icons8-keyboard-50")?.withRenderingMode(.alwaysOriginal), style: .plain, target: self, action: #selector(resetTapped))
    let imageAdd = UIBarButtonItem(image: UIImage(named: "icons8-font-size-50")?.withRenderingMode(.alwaysOriginal), style: .plain, target: self, action: #selector(fontTapped))
    let font = UIBarButtonItem(image: UIImage(named: "icons8-image-80")?.withRenderingMode(.alwaysOriginal), style: .plain, target: self, action: #selector(resetTapped))
    bar.items = [font,flex,imageAdd,reset]
    bar.sizeToFit()
    writePost.inputAccessoryView = bar 
}

@objc func resetTapped() {
    view.endEditing(true)
}

@objc func fontTapped() {
    writePost.font = UIFont.boldSystemFont(ofSize: 12) 
}