我喜欢@nerdist的解决方案。在此基础上，我创建了UITextView的扩展:

import Foundation
import UIKit

extension UITextView
{
  private func add(_ placeholder: UILabel) {
    for view in self.subviews {
        if let lbl = view as? UILabel  {
            if lbl.text == placeholder.text {
                lbl.removeFromSuperview()
            }
        }
    }
    self.addSubview(placeholder)
  }

  func addPlaceholder(_ placeholder: UILabel?) {
    if let ph = placeholder {
      ph.numberOfLines = 0  // support for multiple lines
      ph.font = UIFont.italicSystemFont(ofSize: (self.font?.pointSize)!)
      ph.sizeToFit()
      self.add(ph)
      ph.frame.origin = CGPoint(x: 5, y: (self.font?.pointSize)! / 2)
      ph.textColor = UIColor(white: 0, alpha: 0.3)
      updateVisibility(ph)
    }
  }

  func updateVisibility(_ placeHolder: UILabel?) {
    if let ph = placeHolder {
      ph.isHidden = !self.text.isEmpty
    }
  }
}

例如，在ViewController类中，我是这样使用它的:

class MyViewController: UIViewController, UITextViewDelegate {
  private var notePlaceholder: UILabel!
  @IBOutlet weak var txtNote: UITextView!
  ...
  // UIViewController
  override func viewDidLoad() {
    notePlaceholder = UILabel()
    notePlaceholder.text = "title\nsubtitle\nmore..."
    txtNote.addPlaceholder(notePlaceholder)
    ...
  }

  // UITextViewDelegate
  func textViewDidChange(_ textView: UITextView) {
    txtNote.updateVisbility(notePlaceholder)
    ...
  }

UITextview的占位符!

更新:

如果你在代码中改变textview的文本，记得调用updateVisibitly方法来隐藏占位符:

txtNote.text = "something in code"
txtNote.updateVisibility(self.notePlaceholder) // hide placeholder if text is not empty.

为了防止占位符被添加多次，在扩展中添加了一个私有add()函数。

我不得不调度队列，让我的占位符文本重新出现，一旦编辑完成。

func textViewDidBeginEditing(_ textView: UITextView) {

    if textView.text == "Description" {
        textView.text = nil
    }
}

func textViewDidEndEditing(_ textView: UITextView) {

    if textView.text.isEmpty {
        DispatchQueue.main.async {
            textView.text = "Description"
        }
    }
}

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。

协议版本的clearlight的答案上面，因为协议是伟大的。随便放哪都行。扣篮!

extension UITextViewPlaceholder where Self: UIViewController {

    // Use this in ViewController's ViewDidLoad method.
    func addPlaceholder(text: String, toTextView: UITextView, font: UIFont? = nil) {
        placeholderLabel = UILabel()
        placeholderLabel.text = text
        placeholderLabel.font = font ?? UIFont.italicSystemFont(ofSize: (toTextView.font?.pointSize)!)
        placeholderLabel.sizeToFit()
        toTextView.addSubview(placeholderLabel)
        placeholderLabel.frame.origin = CGPoint(x: 5, y: (toTextView.font?.pointSize)! / 2)
        placeholderLabel.textColor = UIColor.lightGray
        placeholderLabel.isHidden = !toTextView.text.isEmpty
    }

    // Use this function in the ViewController's textViewDidChange delegate method.
    func textViewWithPlaceholderDidChange(_ textView: UITextView) {
        placeholderLabel.isHidden = !textView.text.isEmpty
    }
}

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()
}

基于这里已经给出的一些很好的建议，我能够将以下轻量级的、与接口生成器兼容的UITextView子类组合在一起，它是:

包括可配置的占位符文本，样式就像UITextField一样。 不需要任何额外的子视图或约束。 不需要来自ViewController的任何委托或其他行为。 不需要任何通知。 保持占位符文本与查看字段文本属性的任何外部类完全分离。

任何改进建议都是受欢迎的，特别是如果有任何方法通过编程来获取iOS的占位符颜色，而不是硬编码它。

斯威夫特v5:

import UIKit
@IBDesignable class TextViewWithPlaceholder: UITextView {
    
    override var text: String! { // Ensures that the placeholder text is never returned as the field's text
        get {
            if showingPlaceholder {
                return "" // When showing the placeholder, there's no real text to return
            } else { return super.text }
        }
        set { super.text = newValue }
    }
    @IBInspectable var placeholderText: String = ""
    @IBInspectable var placeholderTextColor: UIColor = UIColor(red: 0.78, green: 0.78, blue: 0.80, alpha: 1.0) // Standard iOS placeholder color (#C7C7CD). See https://stackoverflow.com/questions/31057746/whats-the-default-color-for-placeholder-text-in-uitextfield
    private var showingPlaceholder: Bool = true // Keeps track of whether the field is currently showing a placeholder
    
    override func didMoveToWindow() {
        super.didMoveToWindow()
        if text.isEmpty {
            showPlaceholderText() // Load up the placeholder text when first appearing, but not if coming back to a view where text was already entered
        }
    }
    
    override func becomeFirstResponder() -> Bool {
        // If the current text is the placeholder, remove it
        if showingPlaceholder {
            text = nil
            textColor = nil // Put the text back to the default, unmodified color
            showingPlaceholder = false
        }
        return super.becomeFirstResponder()
    }
    
    override func resignFirstResponder() -> Bool {
        // If there's no text, put the placeholder back
        if text.isEmpty {
            showPlaceholderText()
        }
        return super.resignFirstResponder()
    }
    
    private func showPlaceholderText() {
        showingPlaceholder = true
        textColor = placeholderTextColor
        text = placeholderText
    }
}