@ankitpati, these are some useful docs for adding parsers from Exuberant CTags project (which Universal CTags is a fork of), I presume they mostly still apply:
http://ctags.sourceforge.net/parser.html http://ctags.sourceforge.net/EXTENDING.html
There's this VIM config file which shows the command-line based custom Swift regex parser some people use (no idea how well it works), which could be ported to a compiled regexp parser as per above docs:
https://github.com/keith/swift.vim/commit/5d5f81483d1ecc611c0dcd2846aab872f0...
According to @b4n the main limitation with a regexp-based parser is that it can't handle stuff like scope information, while a character-based parser can support this since it can maintain own state during the parse, if I understood correctly.