CODEWITHSUNDEEP
ruby-on-railsdatabasecustomizationrails-generators
Pamela Cook - LightBe Corp
Pamela Cook - LightBe Corp

Reputation: 4052

How Do I Create A Custom Rails Generate Model function?

I have a Rails 5 application that has separate migrations for three databases. I'm adding a new database. I normally do a rails g model field1:type1 field2:type2 field3:type.... to create my database tables with the desired fields. I want to create generate model statements where it will generate the model for the desired database and put it in the corresponding db/migrate folder.

I have custom database migration generators for the additional databases in lib/generators. Here is an example of the custom migration generator. 

lib/generators/stats_migration_generator.rb

require 'rails/generators/active_record/migration/migration_generator'

class StatsMigrationGenerator < ActiveRecord::Generators::MigrationGenerator
  source_root File.join(File.dirname(ActiveRecord::Generators::MigrationGenerator.instance_method(:create_migration_file).source_location.first), "templates")

  def create_migration_file
    set_local_assigns!
    validate_file_name!
    migration_template @migration_template, "db_stats/migrate/#{file_name}.rb"
  end
end

I assume I need to create lib/generators/mydb_model_generator.rb or whatever the correct filename structure is for each additional database. I'm thinking I could do something like this after looking at the model_generator.rb file in GitHub.

lib/generators/stats_model_generator.rb

require 'rails/generators/active_record/model/model_generator'

class StatsModelGenerator < ActiveRecord::Generators::ModelGenerator
  source_root File.join(File.dirname(ActiveRecord::Generators::ModelGenerator.instance_method(:create_migration_file).source_location.first), "templates")

  def create_migration_file
    set_local_assigns!
    validate_file_name!
    migration_template @migration_template, "db_stats/migrate/#{file_name}.rb"
  end
end

Here are my questions after looking at the git repository for Rails, the Rails Guide regarding creating and customizing Generators and the Ruby on Rails API documentation:

  1. How do I find what I need to require?
  2. How do I find what method I need to override the db/migrate folder name?
  3. How do I find out how to name the rb file for the model generator?

Are my assumptions correct in my attempt to create the model generator?

Upvotes: 2

Views: 1328

Answers (1)

Pamela Cook - LightBe Corp
Pamela Cook - LightBe Corp

Reputation: 4052

Well I did not think I would find the solution so quickly. I took another look at model_generator.rb in GitHub and had an aha moment. I realized that I just needed to replace the method in the default generator with my version which points to the db migrate folder I want. Here is the solution I came up with.

require 'rails/generators/active_record/model/model_generator'

class MydbModelGenerator < ActiveRecord::Generators::ModelGenerator
  source_root File.join(File.dirname(ActiveRecord::Generators::ModelGenerator.instance_method(:create_migration_file).source_location.first), "templates")

  def create_migration_file
    return unless options[:migration] && options[:parent].nil?
    attributes.each { |a| a.attr_options.delete(:index) if a.reference? && !a.has_index? } if options[:indexes] == false
    migration_template "../../migration/templates/create_table_migration.rb", File.join("db_mydb/migrate", "create_#{table_name}.rb")
  end
end

Now I can do rails g mydb_model field1:type1 field2:type2 field3:type and it creates the model migration file in the correct migration folder.

Upvotes: 3

Related Questions