Question

I have a small app that allows users to upload recipes and save favourite recipes. I have a separate model called country that has all the countries of the world within it which then allows users to select one from a dropdown.

Initially I had the association as

recipe

has_one :country

country

belongs_to :recipe

After some research the correct association is

recipe

belongs_to :country

country

belongs_to :recipe

The foreign key country_id going within the recipe model.

I’m going to do some more reading but was wondering if someone could explain as to why it is this association and not the first one

Answer 1

I guest you want to build association like this:

• country can has many recipe
• recipe belongs to one country

If so, you should define association is:

country:

has_many :recipes

recipe:

belongs_to :country

And i think your second association is also incorrect.

When you define belongs_to :country in Recipe model, it means your Recipe table must have a column called country_id. It is a foreign key to Country model.

In the first define association, the Country model will have a column called recipe_id, so, every country just has only one recipe, that’s not what you want, right? Why it’s not work? Because with one country you have only one record, so one country can have only one recipe, accessed through recipe_id.

With first association, your association is One-to-One (One Country has one Recipe), while you actually want your association is One-to-Many ( One Country has Many Recipe). So it’s reason why first association not works (second too).

The main thing you need to remember here is, what model you put a belongs_to association, that model will have a column called 'association name'_id. The different between using has_one and belongs_to only is where you put foreign key and the meaning of association. Check here to clearer.