How to use seed.rb to selectively populate development and/or production databases?

I am using seed.rb to populate both my development and production database. I usually populate the first with dummy data and the latter with the real minimal data that my app needs to run (e.g. the first user and so on).

How can I specify in seed.rb for what environment each data is?

Given that I know "group" to be a Gemfile method, I'd like to achieve the same behavior for seed.rb.

E.g. I'd like to write something like this in my seed.rb:

group :development do 
  # development specific seeding code
end

group :production do 
  # production specific seeding code
end

# non-specific seeding code (it always runs) 

This to be able to call both the development-specific and the non-specific code with

$ rake db:seed

And to call both the production-specific and the non-specific code with:

$ rake db:seed RAILS_ENV=production 

Thank you

seeds.rb is just a plain ruby file, so there are several ways you could approach this. How about a case statement?

# do common stuff here

case Rails.env
when "development"
   ...
when "production"
   ...
end

Another approach could be creating:

db/seeds/development.rb
db/seeds/production.rb
db/seeds/any_other_environment.rb

Then in db/seeds.rb:

# Code you want to run in all environments HERE
# ...
load(Rails.root.join( 'db', 'seeds', "#{Rails.env.downcase}.rb"))

Then write the code you want to run for each environment in the respective file.

another approach, quite similar to @fabro's answer: add a folder seeds to db/ with the environment names and another named common.rb, so you get something like:

db/seeds/common.rb
db/seeds/development.rb
db/seeds/staging.rb
db/seeds/production.rb

than, in your seed.rb:

ActiveRecord::Base.transaction do
  ['common', Rails.env].each do |seedfile|
    seed_file = "#{Rails.root}/db/seeds/#{seedfile}.rb"
    if File.exists?(seed_file)
      puts "- - Seeding data from file: #{seedfile}"
      require seed_file
    end
  end
end

I perfer running the seed in one transaction