这就是我所做的。倾向于代码清晰和简单。我需要添加一个textView，将获得一些额外的笔记在我的应用程序。这额外的笔记可以创建或保存后修改。见下文。HTH。：）

class NotesTextView: UITextView {

    var placeholder = "" {
        didSet {
            showPlaceholder()
        }
    }
    
    // if the text is the placeholder, then assign a color fitting for a
    // placeholder text, else, assign it your color of choice.
    override var text: String! {
        didSet {
            textColor = text == placeholder ? .tertiaryLabel : .systemBlue
        }
    }
    
    
    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        
        delegate = self
        //config your font and translateAutoResizingMaskIntoConstraints here
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    private func showPlaceholder() {
        text = placeholder
    }
    
    private func hidePlaceholder() {
        text = ""
    }
}

extension NotesTextView: UITextViewDelegate {
    func textViewDidBeginEditing(_ textView: UITextView) {
        if text == placeholder {
            hidePlaceholder()
        }
    }
    
    func textViewDidEndEditing(_ textView: UITextView) {
        if text.isEmpty {
            showPlaceholder()
        }
    }
}

不，没有任何占位符可用的textview。你必须把标签上面，当用户进入textview，然后隐藏它或设置默认值时，用户输入删除所有值。

文本视图委托方法

使用这两个委托方法，并在类中编写UITextViewDelegate

func textViewDidBeginEditing(_ textView: UITextView) {
    if (commentsTextView.text == "Type Your Comments")
    {
        commentsTextView.text = nil
        commentsTextView.textColor = UIColor.darkGray
    }
}

func textViewDidEndEditing(_ textView: UITextView) {
    if commentsTextView.text.isEmpty
    {
        commentsTextView.text = "Type Your Comments"
        commentsTextView.textColor = UIColor.darkGray
    }
    textView.resignFirstResponder()
}

在视图加载中设置值

    txtVw!.autocorrectionType = UITextAutocorrectionType.No
    txtVw!.text = "Write your Placeholder"
    txtVw!.textColor = UIColor.lightGrayColor()



func textViewDidBeginEditing(textView: UITextView) {
    if (txtVw?.text == "Write your Placeholder")

    {
        txtVw!.text = nil
        txtVw!.textColor = UIColor.blackColor()
    }
}

func textViewDidEndEditing(textView: UITextView) {
    if txtVw!.text.isEmpty
    {
        txtVw!.text = "Write your Placeholder"
        txtVw!.textColor = UIColor.lightGrayColor()
    }
    textView.resignFirstResponder()
}

这是我准备使用的解决方案，如果您正在处理多个文本视图

func textViewShouldBeginEditing(textView: UITextView) -> Bool {        
    // Set cursor to the beginning if placeholder is set
    if textView.textColor == UIColor.lightGrayColor() {
        textView.selectedTextRange = textView.textRangeFromPosition(textView.beginningOfDocument, toPosition: textView.beginningOfDocument)
    }

    return true
}

func textView(textView: UITextView, shouldChangeTextInRange range: NSRange, replacementText text: String) -> Bool {
    // Remove placeholder
    if textView.textColor == UIColor.lightGrayColor() && text.characters.count > 0 {
        textView.text = ""
        textView.textColor = UIColor.blackColor()
    }

    if text == "\n" {
        textView.resignFirstResponder()
        return false
    }

    return true
}

func textViewDidChange(textView: UITextView) {
    // Set placeholder if text is empty
    if textView.text.isEmpty {
        textView.text = NSLocalizedString("Hint", comment: "hint")
        textView.textColor = UIColor.lightGrayColor()
        textView.selectedTextRange = textView.textRangeFromPosition(textView.beginningOfDocument, toPosition: textView.beginningOfDocument)
    }
}

func textViewDidChangeSelection(textView: UITextView) {
    // Set cursor to the beginning if placeholder is set
    let firstPosition = textView.textRangeFromPosition(textView.beginningOfDocument, toPosition: textView.beginningOfDocument)

    // Do not change position recursively
    if textView.textColor == UIColor.lightGrayColor() && textView.selectedTextRange != firstPosition {
        textView.selectedTextRange = firstPosition
    }
}

与这篇文章中几乎所有的答案相反，UITextView确实有一个占位符属性。由于我无法理解的原因，它只在IB中出现，例如:

<userDefinedRuntimeAttributes>
  <userDefinedRuntimeAttribute type="string" keyPath="placeholder" value="My Placeholder"/>
</userDefinedRuntimeAttributes>

因此，如果你正在使用故事板，一个静态占位符就足够了，只需在检查器上设置属性。

你也可以像这样在代码中设置这个属性:

textView.setValue("My Placeholder", forKeyPath: "placeholder")

它的多云天气，这是通过私有API访问，因为属性是暴露的。

我还没有尝试过用这种方法提交。但我将很快以这种方式提交，并将相应地更新这个答案。

更新:

我已经在多个版本中发布了这个代码，苹果没有任何问题。

更新: 这将只适用于Xcode pre 11.2