如何在Rails中建模以下内容？

Question

I am using Rails 3.2.8 and mySql as the db. I have two models, Setup and Regions. I can have only N regions (N right now being 6) and there can be many setups of which each setup has to be in one Region.

The most obvious way seems to be Setup has_one Region. However this gives every new setup a new region object. However, I wish to reuse the region object in a setup (so that when its parameters change, they change across the board for all setups) and not create a new Region for every setup I have. I am thinking the best way is the following

class Setup < ActiveRecord::Base
    attr_accessible :name, :region_id
end

class Region < ActiveRecord::Base
    attr_accessible :name
end

If I want the region associated with the setup in the controller I do

setup = Setup.find(id)
region = Region.find(setup.region_id)

I am just wondering aloud whether this is the way it is done or is there any other way to capture this in Rails with ActiveRecord or is there any neat abstraction around it so that i can do something like the following?

region = setup.region

Answer 1

You probably want to do things the opposite to your first inclination -- Region has_many :setups , and Setup belongs_to :region (which would require Setup having a :region_id column, as you were thinking). Then, through the magic of Rails associations, Rails will give provide a number of association methods linking the two objects, such as:

@setup.region # the region associated with that setup
@region.setups # all setups associated with the region

There are a bunch of association methods -- I'd recommend reading the Association Basics guid to familiarize yourself with them, particular the references for the has_many and belongs_to associations.

Answer 2

use association in Setup model use belongs_to :region and Region model has_many :setups

Like below:--

class Setup < ActiveRecord::Base
  attr_accessible :name
  belongs_to :region
end

class Region < ActiveRecord::Base
  attr_accessible :name
  has_many :setups
end

Then you can do
setup = Setup.find(id)
region = setup.region

Answer 3

听起来您的安装程序belongs_to一个Region。