How to generate create table migration file using Rails::Generators.invoke("active_record:migration")?

Question

When I used this code

Rails::Generators.invoke("active_record:migration","create_tests",{:behavior=>:invoke, :destination_root=>Rails.root})

to generate migration file, I got the following class generated:

class CreateTests < ActiveRecord::Migration
  def up
  end

  def down
  end
end

But what I want is this:

class CreateTests < ActiveRecord::Migration
  def change
    create_table :tests do |t|

      t.timestamps
    end
  end
end

I'm not aware of what parameters I need to pass inside the invoke method.

Answer 1

You can create template file and use it for generation purposes.

    class CoolMessageGenerator < Rails::Generators::Base
      source_root File.expand_path('../templates', __FILE__)
      argument :model_name, :type => :string, :default => 'CoolMessage'

      def migration
        template 'cool_migration.rb',
                 File.join('db', 'migrate', "#{Time.now.to_i}_create_#{model_name.tableize}.rb")
      end
    end

and templates/cool_migration.rb in same directory:

class Create<%= model_name.pluralize %> < ActiveRecord::Migration
  def change
    create_table :<%= model_name.tableize %> do |t|
      t.timestamps
    end
  end
end