57 lines
2.9 KiB
Plaintext
57 lines
2.9 KiB
Plaintext
db_populate
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===========
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db_populate is an answer to the question "how do I get seed data into a Rails application?"
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Seed data is normally the contents of lookup tables that are essential to the normal
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functioning of your application: lists of roles, administrative accounts, choices for
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dropdown boxes, and so on.
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The inspiration (and some of the code) for this plugin come from a blog entry by Luke
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Francl (http://railspikes.com/2008/2/1/loading-seed-data) that looked at some of the
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available alternatives for loading seed data. Some more of the code came from Josh
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Knowles' db_populate plugin (http://code.google.com/p/db-populate/). But I didn't like
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having to assemble bits, and had some ideas to extend it, and...well, you know how it
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goes.
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Using db_populate
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=================
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The basic idea behind db_populate is simple: to put seed data in your application's
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tables, it executes ruby code. The code needs to be in a specific place, and there's a
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helper to make it easier to create and update consistent seed data. Then there are a
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couple of rake tasks. That's it.
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Setting up for db_populate
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==========================
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To get started with db_populate, create the folder db/populate in your Rails application.
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Any code you put in this folder will be run by db_populate. Optionally, you can create
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subfolders for your Rails environments, just as you can with config files. db_populate
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executes all of the top-level populate files first, followed by any environment-specific
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populate files, sorting each list by name. So, for example, with 4 files in the production
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environment, db_populate would order this way:
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db/populate/01_roles.rb
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db/populate/02_services.rb
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db/populate/production/01_users.rb
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db/populate/production/02_options.rb
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Within each file, you can place whatever ruby code you like. To help create consistent
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records, db_populate adds create_or_populate to ActiveRecord::Base. This method looks up
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a record by ID; if the record exists, it is updated, and if it doesn't, it is created. Using
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this technique means that you can edit and re-run your db_populate tasks without damaging
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data that have already been loaded once. For example, assuming your roles table has already
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been populated, a db_populate file to create an administrative user might look like this:
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user = User.create_or_update(:id => 1, :login => "admin", :email => "admin@example.com",
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:name => "Site Administrator", :password => "admin", :password_confirmation => "admin")
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role = Role.find_by_rolename('administrator')
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Permission.create_or_update(:id => 1, :role_id => role.id, :user_id => user.id)
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If you change your mind about the name for the site administrator, you can just edit the data
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and re-run the task.
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db_populate rake tasks
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======================
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db_populate includes two rake tasks:
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rake db:populate loads all of the data for the current environment
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rake db:migrate_and_populate is the same as calling rake db:migrate followed by rake db:populate |