Developing a RubyGem? You can now have a
script/generate command, just like Rails. Other projects, say like Merb, can do this too.
Awesomeness with a Gold Star. (disclosure: Dr Nic awarded this Gold Star to himself)
This article can get confusing.
Especially around the heading “Generating Generators”.
So, give yourself time to digest it all, and then perhaps come back and read it again.
And then perhaps re-write the article for me.
“A generator that can provide generators to your projects, so that you can write generators for your other projects.”
Re-write it – I dare you.
One of the killer features of Rails is the Rails Generator.
It does three things:
- generates an entire scaffold for your application, thus sharing with you its conventions (over configuration) methodology; and
- it then allows you to generate more stuff, like models, controllers, plugins etc. Things that are relevant to a Rails app. Finally,
- it allows you to write your own generators for Rails apps.
Now you can do all this with New Gem.
Killer Feature #1 – upgrade path
Never before have you been able to run ‘newgem’ on top of an existing RubyGem. Why? It used to blow away the entire folder, and then start writing new files… not very friendly.
Now, just like the
rails command, you can go into your RubyGem development directory, and run
newgem . and you will be asked which files to override.
NOTE: Copy your Rakefile to Rakefile.old, and after running
newgem . copy the configuration information into the new file
If you’re using newgem already, I dare you to upgrade as above. (Ok, perhaps make a backup copy of your work first…)
Killer Feature #2 – script/generate
Once you’ve upgraded, or create a new RubyGem (using
newgem gemname), you’ll now have two scripts:
script/destroy, just like Rails has. (and matching generate.cmd and destroy.cmd for Windows users)
Try them out:
script/generate ... Installed Generators Rubygems: application_generator, component_generator, executable, install_jruby, install_rspec, install_website Builtin: test_unit
Oh yeah, I’ve had some fun extracting things into generators.
- Install the dubious-looking NewGem website –
- Install RSpec support –
- Make the RubyGem a JRuby gem –
script/generate install_jruby(the generated gem will have
-jruby.gemin its name)
- Create an executable Ruby app –
script/generate executable appname
These generators are also reused via the newgem commands various options (Run
newgem to see them.)
Killer Feature #3 – generate generators
I’ll post more about RubiGen later, but you can create a new
rails-like command-line app that generates a whole stack load of directories and files using
script/generate application_generator appname.
There is a large USAGE rundown if you run
Want to create your own generators for developing RubyGems? (similar to creating a generator for a Rails app, but for RubyGems)
script/generate component_generator foobar rubygems create rubygems_generators/foobar/templates exists test create rubygems_generators/foobar/foobar_generator.rb create test/test_foobar_generator.rb create test/test_generator_helper.rb create rubygems_generators/foobar/USAGE readme readme
test/test_generatorname_generator.rb – that’s right, you get a test stub for your new generator. Start there, write tests, then write your generator. There’s inline help for useful assertions.
rubygems_generators folder. This folder is the “scope” of the generator. As it starts with “rubygems” the generator will only be available when you are developing rubygems. It will not show up in Rails, nor Merb or Camping or any other place that may support RubiGen one day.
Similarly, if you want to write a Rails generator using the
component_generator then specify the scope as
script/generate component_generator booya rails create rails_generators/booya/templates exists test create rails_generators/booya/booya_generator.rb create test/test_booya_generator.rb identical test/test_generator_helper.rb create rails_generators/booya/USAGE readme readme
In Edge Rails (and any Rails version after 1.2.3), the
script/generate command in Rails will search all RubyGems for /rails_generator/* folders in addition to the existing search paths (ticket).
Thanks goes to Rails Generator
I’ve long been in love with the Rails Generator for what it does, the beautiful syntax for specifying a generator, etc.
I don’t know who wrote what bit, e.g. if DHH wrote all of it, or others wrote nice chunks, but its awesome. Thanks DHH and co. Thanks to Jeremy Kemper
RubiGen is 95% Rails Generator code, with extensions to support scoping. Setting Rails Generator free of its Rails constraints is a tribute to it.
Now RubyGems can use generators, and any other frameworks can integrate generators and their developers can write and distribute additional generators for those frameworks.
I award myself 2 gold stars, and a scratch-n-sniff
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