I've read the guide on associations but I feel like I'm still not completely comprehending so I want to ask a couple of questions just to be sure. Let's say I am making an app that will, among other things, list large cities all over the world. I would plan on having a view that starts at continent level and can be filtered down. So I would start with a Continent model. And then a Country model. Now, within the Continent model I would define an association as has_many :countries. And in the Country model I would use belongs_to :continents. That much I grasp. So my next model would be a model for states / province. Let's just call it Province since that is more common throughout the world. So now I have my Province model, and I would use belongs_to :country. And likewise Countries would have has_many :provinces. My first question is, how do I describe the association between Province and Continent? Has_many through describes associations where both models have many. A Province only has one Continent. Has_one through describes a relationship between objects that have a one to one relationship via a third object. Again, this isn't the case because a Continent will have many Provinces. So that is my primary question.. how to describe relationships that exist in a one to many through context. My second question would be just asking for tips on writing the migrations for this in a situation where I add another layer, say County, later on. But the main problem is just understand how to express the relationships I described. Or if they even need to be expressed.
ETA: If I were to use the has_many_through association, do I necessarily need to create a join table ( continent_province ), or can I simply use the countries table ie has_many :provinces -> through :countries?