textview 限制字符数

参考

- (void)textViewDidChange:(UITextView *)growingTextView{

NSString *toBeString = growingTextView.text;
    NSString *lang = [growingTextView.textInputMode primaryLanguage];
    if ([lang isEqualToString:@"zh-Hans"]) {// 简体中文输入，包括简体拼音，健体五笔，简体手写
        UITextRange *selectedRange = [growingTextView markedTextRange];
        UITextPosition *position = [growingTextView.internalTextView positionFromPosition:selectedRange.start offset:0];
        // 没有高亮选择的字，则对已输入的文字进行字数统计和限制
        if (!position) {
            if (toBeString.length > MAXLENGTH) {
                growingTextView.text = [toBeString substringToIndex:MAXLENGTH];
            }
        }
        // 有高亮选择的字符串，则暂不对文字进行统计和限制
        else{
        }
    }else {// 中文输入法以外的直接对其统计限制即可，不考虑其他语种情况
        if (toBeString.length > MAXLENGTH) {
            growingTextView.text = [toBeString substringToIndex:MAXLENGTH];
        }
    }
    self.tipLabel.text = [NSString stringWithFormat:@"%lu/30",growingTextView.text.length];
}