REGEX_USERNAME constant
String
const REGEX_USERNAME
Regex of username.
scope for "a-z", "A-Z", "0-9", "_", "Chinese character"
can't end with "_"
length is between 6 to 20
Implementation
static const String REGEX_USERNAME =
"^[\\w\\u4e00-\\u9fa5]{6,20}(?<!_)\$";