Dynamic migrations for rails


  require 'erb'
class ClientMigrator
  def self.create(fields)
    erb_migration = ERB.new <<-EOS
  class AddClients < ActiveRecord::Migration
    def self.up
      create_table :clients do |t|
        <% fields.each do |name, type| %>t.column :<%= name %>, :<%= type %>
        <% end %>
      end
    end

    def self.down
      drop_table :clients
    end
  end
EOS
    File.open("db/migrate/003_add_clients.rb", "w+") do |f|
      f.puts erb_migration.result(binding)
    end
    `rake db:migrate`
  end
end

# Example call
ClientMigrator.create(:name => :string, :phone => :string)
  How do you create a rails project if you don't know the schema in advance? ERB to the rescue!

Blogged background: http://www.danielharan.com/2007/10/12/rails-migration-hackery-with-erb/
  2007-10-12T04:27:08+00:00
  78
  Ruby
  dynamic-migrations-for-rails
  1
  Dynamic migrations for rails
  
  2007-10-12T04:30:57+00:00
  3
  
    
      
class ClientMigrator
  def self.create(fields = {})
    fields.each do |field, type|
      ActiveRecord::Base.connection.add_column(:clients, type)
    end
  end
end

ClientMigrator.create(:name => :string, :phone => :string)
      78
      Hrrrm, this is a very confusing bit of code, because I believe the concept shown here is flawed from the start.... BUUUUUT

I wouldn't use migrations for this at all if I was going to do something as dirty as "dynamically" adding fields to a db with Rails. 

This is assuming you just created a `clients` database with whatever default fields.
      2007-10-12T16:27:41+00:00
      399
      Ruby
      5
      2
      On Dynamic migrations for rails
      5
      Hampton