Install pg gem via Bundler on OSX Snow Leopard

I encountered three problems installing the Postgres ruby gem (pg) when using Bundler to install all the gems for a project on my OSX Snow Leopard 10.6 machine.

Firstly, the gem fails to build on Snow Leopard when you use the binary version of Postgres that is distributed by Enterprise DB. To work around this, the Postgres binaires need to be installed using Mac Ports.

Secondly, the pg gem must be installed using additional bash environment variables.

Thirdly, every time you run bundle install, the current version of Bundler hard re-installs all gems listed in ./Gemfile. This means that even if you install the pg gem correctly by hand, bundler will still try to reinstall it.

All three are resolved as below, in my case I am using Postgres 8.4.

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

Edit: removed sudo from bundle command.