对我来说，一个简单而快速的解决方法是:

@IBDesignable
class PlaceHolderTextView: UITextView {

    @IBInspectable var placeholder: String = "" {
         didSet{
             updatePlaceHolder()
        }
    }

    @IBInspectable var placeholderColor: UIColor = UIColor.gray {
        didSet {
            updatePlaceHolder()
        }
    }

    private var originalTextColor = UIColor.darkText
    private var originalText: String = ""

    private func updatePlaceHolder() {

        if self.text == "" || self.text == placeholder  {

            self.text = placeholder
            self.textColor = placeholderColor
            if let color = self.textColor {

                self.originalTextColor = color
            }
            self.originalText = ""
        } else {
            self.textColor = self.originalTextColor
            self.originalText = self.text
        }

    }

    override func becomeFirstResponder() -> Bool {
        let result = super.becomeFirstResponder()
        self.text = self.originalText
        self.textColor = self.originalTextColor
        return result
    }
    override func resignFirstResponder() -> Bool {
        let result = super.resignFirstResponder()
        updatePlaceHolder()

        return result
    }
}

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()
}

浮动的占位符

将占位符标签放置在文本视图之上，通过跟踪文本视图字符计数的变化来设置其字体、颜色和管理占位符可见性，这是简单、安全且可靠的。

斯威夫特5:

class NotesViewController : UIViewController {

    @IBOutlet var textView : UITextView!
    var placeholderLabel : UILabel!
        
    override func viewDidLoad() {
        super.viewDidLoad()
    
        textView.delegate = self
        placeholderLabel = UILabel()
        placeholderLabel.text = "Enter some text..."
        placeholderLabel.font = .italicSystemFont(ofSize: (textView.font?.pointSize)!)
        placeholderLabel.sizeToFit()
        textView.addSubview(placeholderLabel)
        placeholderLabel.frame.origin = CGPoint(x: 5, y: (textView.font?.pointSize)! / 2)
        placeholderLabel.textColor = .tertiaryLabel
        placeholderLabel.isHidden = !textView.text.isEmpty
    }
}

extension NotesViewController : UITextViewDelegate {
    func textViewDidChange(_ textView: UITextView) {
        placeholderLabel.isHidden = !textView.text.isEmpty
    }
}

斯威夫特3.2

extension EditProfileVC:UITextViewDelegate{

    func textViewDidBeginEditing(_ textView: UITextView) {
        if textView.textColor == UIColor.lightGray {
            textView.text = nil
            textView.textColor = UIColor.black
       }
    }
    func textViewDidEndEditing(_ textView: UITextView) {
        if textView.text.isEmpty {
            textView.text = "Placeholder"
            textView.textColor = UIColor.lightGray
        }
    }
}

首先，当用户开始编辑textViewDidBeginEditing调用，然后检查如果文本灰色的颜色意味着用户没有写任何东西，然后设置为textview nil，并将用户文本的颜色更改为黑色。

当用户端编辑textViewDidEndEditing是调用和检查如果用户没有写任何在textview然后文本设置为灰色与文本“占位符”

我试着用clearlight的答案来简化代码。

extension UITextView{

    func setPlaceholder() {

        let placeholderLabel = UILabel()
        placeholderLabel.text = "Enter some text..."
        placeholderLabel.font = UIFont.italicSystemFont(ofSize: (self.font?.pointSize)!)
        placeholderLabel.sizeToFit()
        placeholderLabel.tag = 222
        placeholderLabel.frame.origin = CGPoint(x: 5, y: (self.font?.pointSize)! / 2)
        placeholderLabel.textColor = UIColor.lightGray
        placeholderLabel.isHidden = !self.text.isEmpty

        self.addSubview(placeholderLabel)
    }

    func checkPlaceholder() {
        let placeholderLabel = self.viewWithTag(222) as! UILabel
        placeholderLabel.isHidden = !self.text.isEmpty
    }

}

使用

override func viewDidLoad() {
    textView.delegate = self
    textView.setPlaceholder()
}

func textViewDidChange(_ textView: UITextView) {
    textView.checkPlaceholder()
}

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。