Question

I’m getting back into Ruby on Rails development after somewhat of a hiatus. I’m having trouble working out the proper Model associations and migrations for this simple practice app I’m working on. Basically, I have 3 models:

City, Marker and Category

City -> name:string, desc:text
Marker -> name:string, lat:decimal, lng:decimal
Category -> name:string

A city has multiple markers on a map. Each marker belongs to a category (i.e. Restaurant, Record Store etc). What I have at the moment is:

class City < ActiveRecord::Base
  has_many :markers
end

class Marker < ActiveRecord::Base
  has_one :category
  belongs_to :city
end

class Category < ActiveRecord::Base
  belongs_to :marker
end

I have a feeling I’ve got this wrong. Even if I haven’t, my real trouble is working out the migration. I thought doing something like:

rails generate migration Marker name:string lat:decimal lng:decimal city_id:integer

Would tie up the City/Marker models but it hasn’t worked out that way. I’m really quite new to all this and the associations has ground me to a halt. Any help would be appreciated!

Barry

Answer 1

I think you’re confusing model and migration generators.

If you want to generate a model:

rails generate model Marker name:string lat:decimal lng:decimal city_id:integer

If you want to generate a migration for this model:

rails generate migration AddNameToMarkers name:string