Generate migrations outside Rails

问题:

I'm using ActiveRecord outside Rails. I would want a program to generate the skeleton of a migration ( as well as a system to collect and maintain them ).

Can anyone make a suggestion?

回答1:

Also take a look at new active_record_migrations

回答2:

There is a gem to use Rails Database Migrations in non Rails projects. Its name is "standalone_migrations"

Here is a link

https://github.com/thuss/standalone-migrations

回答3:

If you do not like to use rake, but still get the system part of ActiveRecord::Migration, then you can use the following to handle the ups and downs from plain ruby (without any rails):

require 'active_record'
require 'benchmark'

# Migration method, which does not uses files in db/migrate but in-memory migrations
# Based on ActiveRecord::Migrator::migrate
def migrate(migrations, target_version = nil)

  direction = case
    when target_version.nil?    
      :up 
    when (ActiveRecord::Migrator::current_version == target_version)
      return # do nothing
    when ActiveRecord::Migrator::current_version > target_version
      :down
    else
      :up
  end

  ActiveRecord::Migrator.new(direction, migrations, target_version).migrate

  puts "Current version: #{ActiveRecord::Migrator::current_version}"
end

# MigrationProxy deals with loading Migrations from files, we reuse it
# to create instances of the migration classes we provide
class MigrationClassProxy < ActiveRecord::MigrationProxy 
  def initialize(migrationClass, version)
    super(migrationClass.name, version, nil, nil)
    @migrationClass = migrationClass
  end

  def mtime
    0
  end

  def load_migration
    @migrationClass.new(name, version)
  end    
end

# Hash of all our migrations
migrations = {
  2016_08_09_2013_00 => 
    class CreateSolutionTable < ActiveRecord::Migration[5.0]
      def change          
        create_table :solution_submissions do |t|
          t.string :problem_hash, index: true
          t.string :solution_hash, index: true
          t.float :resemblance
          t.timestamps
        end
      end 
      self # Necessary to get the class instance into the hash!
    end,

  2016_08_09_2014_16 =>  
    class CreateProductFields < ActiveRecord::Migration[5.0]

      # ...

      self
    end
}.map { |key,value| MigrationClassProxy.new(value, key) }

ActiveRecord::Base.establish_connection(
  :adapter => 'sqlite3',
  :database => 'XXX.db'
)

# Play all migrations (rake db:migrate)
migrate(migrations, migrations.last.version)

# ... or undo them (rake db:migrate VERSION=0)
migrate(migrations, 0)

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true
end

class SolutionSubmission < ApplicationRecord

end

回答4:

I have made a minimal example of how to use active record outside of Rails. Rails migrations (Standalone migrations) in non-Rails (and non Ruby) projects.

https://github.com/euclid1990/rails-migration

(Support Rails >= 5.2)

You can refer Rake file in this repo.

回答5:

There is another gem called otr-activerecord. This gem provides following tasks:

• rake db:create
• rake db:create_migration[name]
• rake db:drop
• rake db:environment:set
• rake db:fixtures:load
• rake db:migrate
• rake db:migrate:status
• rake db:rollback
• rake db:schema:cache:clear
• rake db:schema:cache:dump
• rake db:schema:dump
• rake db:schema:load
• rake db:seed
• rake db:setup
• rake db:structure:dump
• rake db:structure:load
• rake db:version

All you need to do is to install it and add a Rakefile with content

load 'tasks/otr-activerecord.rake'
OTR::ActiveRecord.configure_from_file! 'config/database.yml'

I prefer this gem over active_record_migrations or Standalone Migration because those two gems depend on railties, which is almost the entire Rails. For example, Nokogiri takes a long time to compile, and takes a lot of spaces.