First, let’s go ahead and assume you have an app already made, but you haven’t done rails g scaffold yet. We will be editing the rails g scaffold generator.
Editing the Generator Preferences
First, let’s go to our config/application.rb file.
You should see something like this:
require_relative 'boot'
require "rails"
# Pick the frameworks you want:
require "active_model/railtie"
require "active_job/railtie"
require "active_record/railtie"
require "active_storage/engine"
require "action_controller/railtie"
require "action_mailer/railtie"
require "action_view/railtie"
require "action_cable/engine"
require "sprockets/railtie"
# require "rails/test_unit/railtie"
# Require the gems listed in Gemfile, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(*Rails.groups)
module GeneratorApp
class Application < Rails::Application
# Initialize configuration defaults for originally generated Rails version.
# Settings in config/environments/* take precedence over those specified here.
# Application configuration can go into files in config/initializers
# -- all .rb files in that directory are automatically loaded after loading
# the framework and any gems in your application.
# Don't generate system test files.
config.generators.system_tests = nil
end
endLet’s go ahead and add some code to make our preferences known to the app. Copy the following code:
require_relative 'boot'
require "rails"
# Pick the frameworks you want:
require "active_model/railtie"
require "active_job/railtie"
require "active_record/railtie"
require "active_storage/engine"
require "action_controller/railtie"
require "action_mailer/railtie"
require "action_view/railtie"
require "action_cable/engine"
require "sprockets/railtie"
# require "rails/test_unit/railtie"
# Require the gems listed in Gemfile, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(*Rails.groups)
module GeneratorApp
class Application < Rails::Application
# Initialize configuration defaults for originally generated Rails version.
config.generators do |g|
g.orm :active_record
g.template_engine :erb
g.test_framework :test_unit, fixture: false
g.stylesheets false
g.javascripts false
end
# Settings in config/environments/* take precedence over those specified here.
# Application configuration can go into files in config/initializers
# -- all .rb files in that directory are automatically loaded after loading
# the framework and any gems in your application.
# Don't generate system test files.
config.generators.system_tests = nil
end
endAlright, we have created our preferences for what to use when generating the ORM, templating engine, test framework (which you can change to anything, hint: rspec), and stated not to make the stylesheets (no SCSS files) or javascript.
Editing Content of a Generator
We’ve edited the preferences of our generator, however we can edit the content of what is generated as well. Let’s go ahead and edit an index.html.erb file.
Let’s go into our lib/ folder in our app directory. You should see assets/ and tasks/ as folders with nothing in them. Leave them like that.
Add a nested directory within lib/ called templates/, which is our templating, then create a folder within templates/ called erb/, then within erb/ create another folder called scaffold.
We will be editing the rails g scaffold process.
Create a file within scaffold called index.html.erb
Then go to here to find the usual code from Rails for the index.html.erb file.
We will be editing this file directly. Copy and paste it into the index.html.erb.
You should see the following code:
<p id="notice"><%%= notice %></p>
<h1><%= plural_table_name.titleize %></h1>
<table>
<thead>
<tr>
<% attributes.reject(&:password_digest?).each do |attribute| -%>
<th><%= attribute.human_name %></th>
<% end -%>
<th colspan="3"></th>
</tr>
</thead>
<tbody>
<%% @<%= plural_table_name %>.each do |<%= singular_table_name %>| %>
<tr>
<% attributes.reject(&:password_digest?).each do |attribute| -%>
<td><%%= <%= singular_table_name %>.<%= attribute.column_name %> %></td>
<% end -%>
<td><%%= link_to 'Show', <%= model_resource_name %> %></td>
<td><%%= link_to 'Edit', edit_<%= singular_route_name %>_path(<%= singular_table_name %>) %></td>
<td><%%= link_to 'Destroy', <%= model_resource_name %>, method: :delete, data: { confirm: 'Are you sure?' } %></td>
</tr>
<%% end %>
</tbody>
</table>
<br>
<%%= link_to 'New <%= singular_table_name.titleize %>', new_<%= singular_route_name %>_path %>Let’s make some edits.
<p id="notice"><%%= notice %></p>
<h2><%= plural_table_name.titleize %></h2>
<hr>
<div>
<%% @<%= plural_table_name %>.each do |<%= singular_table_name %>| %>
<div>
<% attributes.reject(&:password_digest?).each do |attribute| -%>
<p><%%= <%= singular_table_name %>.<%= attribute.column_name %> %></p>
<% end -%>
<p><%%= link_to 'Show', <%= model_resource_name %> %></p>
<p><%%= link_to 'Edit', edit_<%= singular_route_name %>_path(<%= singular_table_name %>) %></p>
<p><%%= link_to 'Destroy', <%= model_resource_name %>, method: :delete, data: { confirm: 'Are you sure?' } %></p>
</div>
<%% end %>
</div>
<br>
<%%= link_to 'New <%= singular_table_name.titleize %>', new_<%= singular_route_name %>_path %>Instead of a table, we replaced them with div’s and instead of an h1 for the table name, we have an h2. Now, you can insert whatever you want into this file as long as it’s ERB and HTML5, it will run.
Now, we’ve created our own custom generator!
We’re ready to run rails g scaffold!
Conclusion
Congratulations! You’ve created your first custom generator in Rails 5.2!
For further information on generating your own generators, please see this [Rails Guide][https://guides.rubyonrails.org/generators.html]