I’ve been working a lot with seed data in my applications lately, and it’s obviously a problem that can be pretty aggravating to deal with. I ultimately liked the db-populate approach the best with the addition of the ActiveRecord::Base.create_or_update method. My one problem with it is that it’s based entirely on fixed ids for the fixtures, which is a pain to deal with when loading up your attributes from arrays. Here’s an example of what I was doing:

i = 1

{ "admin"     => ["Administrator", 1000], 
  "member"    => ["Member", 1], 
  "moderator" => ["Moderator", 100],
  "disabled"  => ["Disabled User", -1] }.each_pair do |key, val|
  Role.create_or_update(:id => i, :key => key, :name => val[0], :value => val[1])
  i += 1
end

I really don’t like having to put the i in there to increment up. Not only is it messier code, but it would be dangerous if I wanted to move around the roles. I also don’t want to have to have an id explicitly in each entry since I really don’t care what the id is. So I thought I would hack up a better solution for this create_or_update scenario and this is what I came up with:

class << ActiveRecord::Base
  def create_or_update(options = {})
    self.create_or_update_by(:id, options)
  end
  
  def create_or_update_by(field, options = {})
    find_value = options.delete(field)
    record = find(:first, :conditions => {field => find_value}) || self.new
    record.send field.to_s + "=", find_value
    record.attributes = options
    record.save!
    record
  end
  
  def method_missing_with_create_or_update(method_name, *args)
    if match = method_name.to_s.match(/create_or_update_by_([a-z0-9_]+)/)
      field = match[1].to_sym
      create_or_update_by(field,*args)
    else
      method_missing_without_create_or_update(method_name, *args)
    end
  end
  
  alias_method_chain :method_missing, :create_or_update
end

Basically, this allows me to call create_or_update with an arbitrary attribute as my “finder” by calling Model.create_or_update_by(:field, ...). To give it a little taste of syntactic sugar, I threw in a method missing to allow you to name a field in the method call itself. So now the code I wrote before can become this:

{ "admin"     => ["Administrator", 1000], 
  "member"    => ["Member", 1], 
  "moderator" => ["Moderator", 100],
  "disabled"  => ["Disabled User", -1] }.each_pair do |key, val|
  Role.create_or_update_by_key(:key => key, :name => val[0], :value => val[1])
end

This is much cleaner and prettier to look at, and also makes sure that it is keying off of the value that I really care about. This new create_or_update combined with db-populate creates the most powerful seed data solution I’ve yet come across.