Rails - After installing the gem, is this step necessary?

If I install a gem, say:

gem install xyz

Must I add this line to the Gemfile?

gem 'xyz'开发者_C百科

Thanks.

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the correct order to do this is to add to your Gemfile then run bundle install.

because if you gem install and don't add to your Gemfile and move the project to another machine it will be very difficult to find which gem was installed.