我遵循了这个链接的代码。只有7个简单的步骤。它添加了一个UILabel的textView和隐藏/显示标签时，文本输入或从textView通过textView的textViewDidChangeSelection(_ textView: UITextView)委托方法。我将步骤放在代码上方的注释中。

// 1. make sure to include the UITextViewDelegate
class YourClass: UITextViewDelegate {

    @IBOutlet weak var textView : UITextView!

    // 2. create placeholder textLabel
    let placeHolderTextLabel: UILabel = {
        let placeholderLabel = UILabel()
        placeholderLabel.text = "Placeholder text..."
        placeholderLabel.sizeToFit()
        placeholderLabel.textColor = UIColor.lightGray
        return placeholderLabel
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        // 3. set textView delegate
        textView.delegate = self

        configurePlaceholderTextLabel()
    }


    func configurePlaceholderTextLabel() {

        // 4. add placeholder label to textView, set it's frame and font
        textView.addSubview(placeHolderTextLabel)
        placeHolderTextLabel.frame.origin = CGPoint(x: 5, y: (textView.font?.pointSize)! / 2)
        placeHolderTextLabel.font = UIFont.systemFont(ofSize: (textView.font?.pointSize)!)

        // 5. decide wether the placeHolderTextLabel is hidden or not depending on if there is or isn't text inside the textView
        placeHolderTextLabel.isHidden = !textView.text.isEmpty

    }

    // 6. implement textView delegate method to update the placeHolderTextLabel when the text is changed
    func textViewDidChangeSelection(_ textView: UITextView) {

        // 7. decide wether the placeHolderTextLabel is hidden or not depending on if there is or isn't text inside the textView when text in textView is changed
        placeHolderTextLabel.isHidden = !textView.text.isEmpty
    }

}

在h课上

@interface RateCommentViewController : UIViewController<UITextViewDelegate>{IBoutlet UITextview *commentTxtView;}

在。m类

- (void)viewDidLoad{      
    commentTxtView.text = @"Comment";
    commentTxtView.textColor = [UIColor lightGrayColor];
    commentTxtView.delegate = self;
}

- (BOOL) textViewShouldBeginEditing:(UITextView *)textView
{
    commentTxtView.text = @"";
    commentTxtView.textColor = [UIColor blackColor];
    return YES;
}

-(void) textViewDidChange:(UITextView *)textView
{
    if(commentTxtView.text.length == 0){
        commentTxtView.textColor = [UIColor lightGrayColor];
        commentTxtView.text = @"Comment";
        [commentTxtView resignFirstResponder];
    }
}

更简单，并且仍然考虑到用户在某些时候输入的一些文本

BOOL placeHolderTextVisible;

在viewDidLoad上，设置它为YES(或DidMoveToSuperview，或awakeFromNib)

然后,在 - (BOOL) textView:(UITextView*)textView shouldBeginEditing

    - (BOOL)textViewShouldBeginEditing:(UITextView *)textView;
{
   if (placeHolderTextVisible) {
    placeHolderTextVisible = NO;
    textView.text = @"";
   }
 return YES;
}

我刚刚发现，在iOS 10中，你现在可以将UITextView转换为方法的UITextField，并在方法中设置占位符。刚试过，它不需要子类化UITextView就能工作。

下面是一个对我有用的例子:

-(void)customizeTextField:(UITextField *)textField placeholder:(NSString *)pText withColor:(UIColor *)pTextColor{

        textField.attributedPlaceholder = [[NSAttributedString alloc]
                                          initWithString:pText
                                          attributes:@{NSForegroundColorAttributeName:pTextColor}];
    }

为了将它用于UITextView，你只需要将它传递给方法，使用像这样的类型转换:

[self customizeTextField:(UITextField*)_myTextView placeholder:@"Placeholder" withColor:[UIColor blackColor]];

注:经过测试，我发现这个解决方案在iOS9上也很好。但是会在iOS8.x上导致崩溃

你能做的是在文本属性中设置文本视图的初始值，并将textColor更改为[UIColor grayColor]或类似的东西。然后，每当文本视图变为可编辑时，清除文本并显示游标，如果文本字段再次为空，则将占位符文本放回。根据需要将颜色更改为[UIColor blackColor]。

它与UITextField中的占位符功能不完全相同，但很接近。

你可以在textview上设置一个标签。

MyUITextView.h

@interface MyUITextView : UITextView {
    UILabel* _placeholderLabel;
}

@property(nonatomic, assign)NSString *placeholder;

MyUITextView.m

@implementation MyUITextView

- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        // Create placeholder
        viewFrame = CGRectMake(0, 0, frame.size.width, 15);
        _placeholderLabel = [[UILabel alloc] initWithFrame:viewFrame];
        _placeholderLabel.textColor = [UIColor lightGrayColor];
        [self addSubview:_placeholderLabel];

        // Add text changed notification 
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
    }
    return self;
}

- (void)setPlaceholder:(NSString *)placeholder {
    _placeholderLabel.text = placeholder;
}

- (NSString*)placeholder {
    return _placeholderLabel.text;
}

#pragma mark UITextViewTextDidChangeNotification

- (void)textChanged:(NSNotification *)notification {
    _placeholderLabel.hidden = ([self.text lenght] == 0);
}

@end