UITextView的placehoder实现带并限制100字

1.在viewdidload中添加一个默认字体的lable

placeHoderLable = [[UILabel alloc]initWithFrame:CGRectMake(3, 3, DeviceWidth-6, 40)];//根据情况调节位置
placeHoderLable.enabled = NO;
placeHoderLable.text = @"请在这里输入您要预测的内容，您的预言需要经过其他用户的审核才能发布。";
placeHoderLable.numberOfLines=0;
placeHoderLable.font =  [UIFont systemFontOfSize:12];
placeHoderLable.textColor = [UIColor lightGrayColor];
[_myTextView addSubview:placeHoderLable];
_myTextView.delegate=self;//记得设置textview的代理
_myTextView.returnKeyType=UIReturnKeyDone;

2.在textview的代理方法中实现以下代码

-(void)textViewDidChange:(UITextView *)textView
      {
        if ([_myTextView.text length] == 0) {
            [placeHoderLable setHidden:NO];
        }else{
            [placeHoderLable setHidden:YES];
        }
    }

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:                                (NSString *)text
{
    if([text isEqualToString:@"\n"]){

        [textView resignFirstResponder];

        return NO;

    }
    if (range.location>=100)
    {
        _yuNumLable.text=@"还能输入0字";
        return  NO;
    }
    else
    {
        _yuNumLable.text=[NSString stringWithFormat:@"还能输入%lu字",100-range.location];
        return YES;
    }
}