关于Rails插件/引擎

Question

I am looking at rails plugins to help me modularize my application. I have some basic questions that I am confused about.

Can a rails plugin have its own DB? My application is very little traffic, for internal use, so I am fine with the idea of separate sqlite DB's for each plugin. When I do a "rails plugin new" even if I use --full, there is no database.yml generated. If I create one and do a rake db:create, no sqlite db is created.

Is there a good tutorial available for creating a rails plugin with rails 3.2? Most I find are older and use the enginex gem which I think is now built into rails.

Can you run your plugin as a standalone app for testing, ie using WEBrick? When I run "rails server" in my plugin directory, it just says "Error: Command not recognized".

I guess that's it, I am just confused on how to begin.

Answer 1

Creating Migrations

The Rails Guide "Getting Started with Engines" instructs you to use 'rails g model post' from the root directory for your engine.

Getting Started with Engines

If you do this, it will create the db/migrate folder for you with the migration inside of it.

$ rails g model post
  invoke  active_record
  create    db/migrate/20120517184738_create_my_engine_posts.rb
  create    app/models/my_engine/post.rb
  invoke    test_unit
  create      test/unit/my_engine/post_test.rb
  create      test/fixtures/my_engine/posts.yml

You can also generate migrations directly just the same, just as you do with a Rails app.

$ rails g migration AddMyEngineTable
  invoke  active_record
  create    db/migrate/20120517185241_add_my_engine_table.rb

Running Rails Server

The Rails Guide also states to run 'rails s' from test/dummy, not from the root of your engine directory.

I see that from an ASCIICast on the subject which covered Rails 3.1 RC5 that you used to be able to run 'rails s' from the root directory of your engine/gem. This is no longer the case.

From the Rails issue posted on Github three months ago it appears that they needed to keep the scope of the engine separate from the scope of the dummy app.

Issue #4894: Mountable Engines Rails File

Answer 2

在短期内从引擎根目录开始：

test/dummy/script/rails s