Fix this error on my Ruby install

I'm new to Ruby and trying to get it to run, but when I do I get this message:

Could not find gem 'sqlite3 (>= 0)' in any of the gem sources listed in your Gemfile. Run bundle install to install missing gems.

after I run "bundle install" on the terminal (using a Mac) I get the following:

Installing sqlite3 (1.3.4) with native extensions /Library/Ruby/Site/1.8/rubygems/installer.rb:551:in `build_extensions': ERROR: Failed to build gem native extension. (Gem::Installer::ExtensionBuildError)

/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby extconf.rb mkmf.rb can't find header files for ruby at /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/ruby.h

How can I fix this? I've been Googling for a while but haven't been able to figure it out, and I need this to 开发者_StackOverflow中文版successfully run "rails server" to see my app on the browser =/

From here:

Can't find header files for ruby

If you get the can't find header files for ruby error message when trying to build an extension or a gem, it means that Ruby cannot locate its header files.

Header files are not delivered by default with Mac OS X, you need to install the Xcode Tools package after the installation. You can find it in the Optional Installs / Xcode Tools directory on the Leopard DVD.

That's it, the system doesn't have the Ruby header files. To install them, you need to install the Xcode Tools package.