UITextView使用相對較少，研究了下發(fā)現(xiàn)代理方法并不多，算是簡單控件了。這里針對字?jǐn)?shù)限制功能的開發(fā)稍作總結(jié)：

//創(chuàng)建UITextView，注意添加代理
    UITextView *textView = [[UITextView alloc]init];
    textView.text = @"占位文字";
    textView.delegate = self;       //UITextViewDelegate
    textView.textColor = hexStringToColor(@"C2C2C2");
    textView.font = [UIFont systemFontOfSize:14];
    [cell.contentView addSubview:textView];
    [textView makeConstraints:^(MASConstraintMaker *make) {
        make.left.mas_offset(15*layoutBy6());
        make.top.mas_offset(10*layoutBy6());
        make.right.mas_offset(-15*layoutBy6());
        make.bottom.mas_offset(-10*layoutBy6());
    }];

#pragma mark - TextViewDelegate
//輸入時(shí)自動刪除占位文字
- (void)textViewDidBeginEditing:(UITextView *)textView{
    if ([textView.text isEqualToString:@"占位文字"]) {
        textView.text = @"";
    }
}

//當(dāng)編輯時(shí)動態(tài)判斷是否超過規(guī)定字?jǐn)?shù)，這里限制20字
- (void)textViewDidChange:(UITextField *)textView{
    
    if (textView.text.length > 20) {
        textView.text = [textView.text substringToIndex:20];
    }
//這里的_strLengthLbl為動態(tài)顯示已輸入字?jǐn)?shù)，可按情況添加
    _strLengthLbl.text = [NSString stringWithFormat:@"%lu/20",textView.text.length];
}

//編輯結(jié)束后如內(nèi)存為空自動添加占位文字
- (void)textViewDidEndEditing:(UITextView *)textView{
    if ([textView.text isEqualToString:@""]) {
        textView.text = @"占位文字";
    }
}