I followed this thread (Cannot install pg gem in Mavericks with Postgres.app) to get the 'pg' gem successfully working with Postgres.app on Mavericks.
Here is the output of gem list:
mythlabs:~ myth$ gem list pg
*** LOCAL GEMS ***
pg (0.17.1)
mythlabs:~ myth$
However, now that I have the gem installed, in irb :
mythlabs:~ myth$ irb
1.9.3-p0 :001 > require 'pg' => true
1.9.3-p0 :002 > conn = PG.connect( dbname: 'myth' ) NameError: uninitialized constant PG from (irb):2 from /Users/myth/.rvm/rubies/ruby-1.9.3-p0/bin/irb:16:in `<main>'
1.9.3-p0 :003 >
How can I go around fixing this problem?