组件--限制文本框字数（处理中文拼音占位的影响）

TextView

-(BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
//    if ([text isEqualToString:@"\n"]) {
//        [textView resignFirstResponder];
//        return NO;
//    }
    
    NSString *totalText = [NSString stringWithFormat:@"%@%@",textView.text,text];
    UITextRange *rangeSelected = textView.markedTextRange;
    NSInteger validTxtLength = textView.text.length;
    if (rangeSelected) { //在拼音的路上
        NSString *selectedText = [textView textInRange:rangeSelected];
        
        if (![self judgeInputIsChinese:text]) {//还是拼音
            validTxtLength = totalText.length-selectedText.length;
            if (validTxtLength > _maxLength) {
                NSString *strValid = [textView.text substringWithRange:NSMakeRange(0, textView.text.length-selectedText.length)];
                NSString *newStr = [strValid stringByAppendingString:text];
                newStr = [newStr substringWithRange:NSMakeRange(0, _maxLength)];
                textView.text = newStr;
                return NO;
            }else{
                return YES;
            }
            
        }else{//拼完输入汉字了！=
            NSString *strValid = [textView.text substringWithRange:NSMakeRange(0, textView.text.length-selectedText.length)];
            NSString *newStr = [strValid stringByAppendingString:text];
            if (newStr.length>_maxLength) {
                newStr = [newStr substringWithRange:NSMakeRange(0, _maxLength)];
            }
            textView.text = newStr;
            return NO;
        }
    }
    
    if (totalText.length > _maxLength && text.length>0){//字段长度超过限制，且本步操作不是删除
        textView.text = [totalText substringToIndex:_maxLength];
        return NO;
    }
    
    if (![totalText isEqualToString:@""]) {
        _txvPlaceholder.hidden = YES;
    }
    
    //删除最后一个字符时
    if ([text isEqualToString:@""] && range.location == 0 && range.length == 1) {
        _txvPlaceholder.hidden = NO;
    }
    
    return YES;
}

//判断是否是全中文字符串
- (BOOL)judgeInputIsChinese:(NSString *)textStr{
    NSString *regex = @"[\u4e00-\u9fa5]+";
    NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
    BOOL isMatch = [pred evaluateWithObject:textStr];
    return isMatch;
    
}

参考文章：

1. iOS ...如何使uitextfield不把输入的拼音认作文本编辑框的内容
2. 正则判断字符串类型