Rails Application Templates¶ ↑
Application templates are simple Ruby files containing DSL for adding gems/initializers etc. to your freshly created Rails project or an existing Rails project.
After reading this guide, you will know:
-
How to use templates to generate/customize Rails applications.
-
How to write your own reusable application templates using the Rails template API.
Usage¶ ↑
To apply a template, you need to provide the Rails generator with the location of the template you wish to apply using the -m option. This can either be a path to a file or a URL.
$ rails new blog -m ~/template.rb $ rails new blog -m http://example.com/template.rb
You can use the rake task rails:template
to apply templates to
an existing Rails application. The location of the template needs to be
passed in to an environment variable named LOCATION. Again, this can either
be path to a file or a URL.
$ bin/rake rails:template LOCATION=~/template.rb $ bin/rake rails:template LOCATION=http://example.com/template.rb
Template API¶ ↑
The Rails templates API is easy to understand. Here's an example of a typical Rails template:
# template.rb generate(:scaffold, "person name:string") route "root to: 'people#index'" rake("db:migrate") after_bundle do git :init git add: "." git commit: %Q{ -m 'Initial commit' } end
The following sections outline the primary methods provided by the API:
gem(*args)¶ ↑
Adds a gem
entry for the supplied gem to the generated
application's Gemfile
.
For example, if your application depends on the gems bj
and
nokogiri
:
gem "bj" gem "nokogiri"
Please note that this will NOT install the gems for you and you will have
to run bundle install
to do that.
bundle install
gem_group(*names, &block)¶ ↑
Wraps gem entries inside a group.
For example, if you want to load rspec-rails
only in the
development
and test
groups:
gem_group :development, :test do gem "rspec-rails" end
add_source(source, options = {})¶ ↑
Adds the given source to the generated application's
Gemfile
.
For example, if you need to source a gem from
"http://code.whytheluckystiff.net"
:
add_source "http://code.whytheluckystiff.net"
environment/application(data=nil, options={}, &block)¶ ↑
Adds a line inside the Application
class for
config/application.rb
.
If options[:env]
is specified, the line is appended to the
corresponding file in config/environments
.
environment 'config.action_mailer.default_url_options = {host: "http://yourwebsite.example.com"}', env: 'production'
A block can be used in place of the data
argument.
vendor/lib/file/initializer(filename, data = nil, &block)¶ ↑
Adds an initializer to the generated application's
config/initializers
directory.
Let's say you like using Object#not_nil?
and
Object#not_blank?
:
initializer 'bloatlol.rb', <<-CODE class Object def not_nil? !nil? end def not_blank? !blank? end end CODE
Similarly, lib()
creates a file in the lib/
directory and vendor()
creates a file in the
vendor/
directory.
There is even file()
, which accepts a relative path from
Rails.root
and creates all the directories/files needed:
file 'app/components/foo.rb', <<-CODE class Foo end CODE
That'll create the app/components
directory and put
foo.rb
in there.
rakefile(filename, data = nil, &block)¶ ↑
Creates a new rake file under lib/tasks
with the supplied
tasks:
rakefile("bootstrap.rake") do <<-TASK namespace :boot do task :strap do puts "i like boots!" end end TASK end
The above creates lib/tasks/bootstrap.rake
with a
boot:strap
rake task.
generate(what, *args)¶ ↑
Runs the supplied rails generator with given arguments.
generate(:scaffold, "person", "name:string", "address:text", "age:number")
run(command)¶ ↑
Executes an arbitrary command. Just like the backticks. Let's say you
want to remove the README.rdoc
file:
run "rm README.rdoc"
rake(command, options = {})¶ ↑
Runs the supplied rake tasks in the Rails application. Let's say you want to migrate the database:
rake "db:migrate"
You can also run rake tasks with a different Rails environment:
rake "db:migrate", env: 'production'
route(routing_code)¶ ↑
Adds a routing entry to the config/routes.rb
file. In the
steps above, we generated a person scaffold and also removed
README.rdoc
. Now, to make PeopleController#index
the default page for the application:
route "root to: 'person#index'"
inside(dir)¶ ↑
Enables you to run a command from the given directory. For example, if you have a copy of edge rails that you wish to symlink from your new apps, you can do this:
inside('vendor') do run "ln -s ~/commit-rails/rails rails" end
ask(question)¶ ↑
ask()
gives you a chance to get some feedback from the user
and use it in your templates. Let's say you want your user to name the
new shiny library you're adding:
lib_name = ask("What do you want to call the shiny library ?") lib_name << ".rb" unless lib_name.index(".rb") lib lib_name, <<-CODE class Shiny end CODE
yes?(question) or no?(question)¶ ↑
These methods let you ask questions from templates and decide the flow based on the user's answer. Let's say you want to freeze rails only if the user wants to:
rake("rails:freeze:gems") if yes?("Freeze rails gems?") # no?(question) acts just the opposite.
git(:command)¶ ↑
Rails templates let you run any git command:
git :init git add: "." git commit: "-a -m 'Initial commit'"
after_bundle(&block)¶ ↑
Registers a callback to be executed after the gems are bundled and binstubs are generated. Useful for all generated files to version control:
after_bundle do git :init git add: '.' git commit: "-a -m 'Initial commit'" end
The callbacks gets executed even if --skip-bundle
and/or
--skip-spring
has been passed.
Advanced Usage¶ ↑
The application template is evaluated in the context of a
Rails::Generators::AppGenerator
instance. It uses the
apply
action provided by Thor.
This means you can extend and change the instance to match your needs.
For example by overwriting the source_paths
method to contain
the location of your template. Now methods like copy_file
will
accept relative paths to your template's location.
def source_paths [File.expand_path(File.dirname(__FILE__))] end