iOS UITextField 限制字符

监听

 [self.textTF addTarget:self action:@selector(textFieldTextChanged:) forControlEvents: UIControlEventEditingChanged];

- (void)textFieldTextChanged:(UITextField *)textField{
   NSString *str = textField.text;
    //中文输入法下
    UITextRange *selectedRange = [self.textTF markedTextRange];
    //高亮部分
    UITextPosition *postion = [self.textTF 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 (!postion) {
            if (str.length > 5 ){ //判断字符是否超过
                self.textTF.text = [str substringToIndex:6];
            }
    }
}

//获取字符长度，中文为2

- (NSInteger )strLength:(NSString *)str {

    NSInteger length = 0;
    for(int i=0; i< [str length];i++) {

        int a = [str characterAtIndex:i];

        if( a > 0x4e00 && a < 0x9fff){//判断输入的是否是中文

            length = length + 2;

        } else {
            length = length + 1;
        }
    }

    return length;

}