将迁移添加到 Rails 引擎的安装生成器答案

【问题标题】：Add Migrations to a Rails Engine's Install Generator将迁移添加到 Rails 引擎的安装生成器
【发布时间】：2017-01-16 20:43:09
【问题描述】：

在我的 rails 5 引擎中，我想使用自定义安装生成器安装引擎迁移：

myengine/lib/generators/myengine/install_generator.rb

这个生成器目前看起来像这样：

module Myengine
  module Generators

    class InstallGenerator < Rails::Generators::Base
      source_root File.expand_path("../../templates", __FILE__)

      desc "Creates a Myengine initializer and copys template files to your application."

      def copy_initializer
        template "myengine.rb", "config/initializers/myengine.rb"
      end

    end
  end
end

当我将引擎添加到 Rails 应用程序时，无需调用：

rails g myengine:install

然后

rails myengine:install:migrations

如何将这些迁移的创建添加到自定义生成器？

【问题讨论】：

标签： ruby-on-rails rails-migrations rails-engines rails-generators

【解决方案1】：

有趣的问题！我希望我能回答一个。假设您有一个名为“Buttafly”的引擎和一个位于以下位置的生成器：

#lib/generators/buttafly/install/install_generator.rb

在生成器的顶部，需要像这样的“日期”库：

require 'date'

然后在生成器的主体中，添加如下方法定义：

  def copy_migrations

    # get an array of the migrations in your engine's db/migrate/ 
    # folder:

    migrations = Dir[Buttafly::Engine.root.join("db/migrate/*.rb")]
    migrations.each_with_index do |migration, i|

    # The migrations will be created with the same timestamp if you 
    # create them all at once. So if you have more than one migration 
    # in your engine, add one second to the second migration's file
    # timestamp and a third second to the third migration's timestamp 
    # and so on:

    seconds = (DateTime.now.strftime("%S").to_i + i).to_s
    seconds = seconds.to_s.length == 2 ? seconds : "0#{seconds}"
    timestamp = (DateTime.now.strftime "%Y%m%d%H%M") + seconds

    # get the filename from the engine migration minus the timestamp:
    name = migration.split("/").split("_").last

    # See if a the name of your engine migration is already in your
    # host app's db/migrate folder:

    if Rails.root.join("db/migrate/*#{name}").exist?

      # do nothing:
      puts "Migration #{name} has already been copied to your app"
    else

      # copy your engine migration over to the host app with a new 
      # timestamp:
      copy_file m, "db/migrate/#{timestamp}_buttafly_#{name}"
    end
  end
end

【讨论】：