Having trouble installing the PG gem - postgresql

Question

I'm trying this, as the docs say:
gem install pg --with-pg-config=/opt/local/lib/postgresql90/bin/pg_config
ERROR: While executing gem ... (OptionParser::InvalidOption)
But, that's obviously not working. Can anyone spot an error?

Answer 1

The example that you're linking to says this:
gem install -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config
#-----------^^
Note the -- in there that you're not using. I suspect that gem is trying to parse the --with-pg-config as an option to gem rather than an option to the gem itself. Just a plain -- in an option list means "stop parsing options here" so try one of these:
gem install -- pg --with-pg-config=/opt/local/lib/postgresql90/bin/pg_config
gem install pg -- --with-pg-config=/opt/local/lib/postgresql90/bin/pg_config
One of those should keep gem from trying to interpret --with-pg-config as a gem option and get it down to the pg gem itself.

Answer 2

Not sure if the other answer works, but I thought I'd point out that the instructions here did work if you're using bundler to manage gems:
http://devblog.vworkapp.com/post/403869225/install-pg-gem-via-bundler-on-osx-snow-leopard
install postgres from Mac Ports
sudo port install postgres84
Include the postgres binaries in the PATH environment variable
export PATH=/opt/local/lib/postgresql84/bin:${PATH}
Then run bundle install with the all-important arch flag
env ARCHFLAGS="-arch x86_64" bundle install
Caveats: Your ARCHFLAGS may be something like i386 and not x86_64, depending on your local environment (and these instructions are obviously installing an older postgres -- I did sudo port install postgresql90).