uitextview的placeholder占位文字

# import "ZHZTextView.h"
 
# define kMargin 7
# define kFontSize 17
 
 @interface ZHZTextView ()<UITextViewDelegate>
 
 @property (nonatomic, strong)UILabel *placeholderLabel;
 
 @end
 
 @implementation ZHZTextView
 
 - (instancetype)initWithFrame:(CGRect)frame
 {
     self = [super initWithFrame:frame];
     if (self) {
         self.delegate = self;
         self.layer.cornerRadius = kMargin;
         self.layer.borderWidth = 1;
         self.font = [UIFont systemFontOfSize:kFontSize];
     }
     return self;
 }
 
 
# pragma mark - UITextViewDelegate
 - (void)textViewDidChange:(UITextView *)textView {
     self.placeholderLabel.hidden = textView.text.length;
 }
 
# pragma mark - getter and setter
 - (UILabel *)placeholderLabel {
     if (_placeholderLabel == nil) {
         _placeholderLabel = [[UILabel alloc] init];
         _placeholderLabel.textColor = [UIColor lightGrayColor];
         _placeholderLabel.numberOfLines = 0;
     }
     return _placeholderLabel;
 }
 
 - (void)setPlaceholder:(NSString *)placeholder {
     if (_placeholder != placeholder) {
         
         //只有在 设置占位文本时 才加载 label
         [self addSubview:self.placeholderLabel];
         
         //设置占位文本
         self.placeholderLabel.text = placeholder;
         
         //文本 frame
         NSDictionary *dict = @{
                                NSFontAttributeName: [UIFont systemFontOfSize:kFontSize]
                                };
        CGRect rect = [placeholder boundingRectWithSize:CGSizeMake(self.frame.size.width - kMargin * 2, 0) options:NSStringDrawingUsesLineFragmentOrigin |NSStringDrawingUsesFontLeading attributes:dict context:nil];
         
         self.placeholderLabel.frame = CGRectMake(kMargin, kMargin, rect.size.width, rect.size.height);
     }
 }
 
 @end

ZHZTextView *textView = [[ZHZTextView alloc] initWithFrame:CGRectMake(50, 20, 275, 375)];
    textView.placeholder = @"是来占位的我是来占位的我是来占位的我是来占位的我是来占位的";
    [self.view addSubview:textView];