Building Relationship between Models

Hi again… :slight_smile:

I’m still working on RoR

right now i’m fighting against relationship.

I generated 3 scaffolds




all the 3 CRUD works and now in the database I’ve many engines , many

wheel and many cars.

I want to correlate this object but how do it ?

I must say that car has_one engine and engine belongs_to car

(every car can have only one engine)

or i must write that engine has_many cars and car belongs_to engine

(one engine is used on many different car)

or I need to create a new scaffold like road_ready_car which has_one

engine , has_one car and has_many wheels

It all depends what you want in the database. Are the cars in the database individual cars, or types of car? If types of car then maybe the name is wrong. Similarly are the engines actual engines or just types of engines? The same for wheels.

If they are all actual individual items then a car has only one engine and an engine has only one car (at any one time at least). A car has 4 wheels (5 including spare?) so car has many wheels, wheel belongs to car.

If, however you are talking about types of cars and engines then a car type may have many engine types and an engine type may have many car types. Perhaps in this case you then need another table for the actual cars where a car is of one car type, one engine type and one wheel type.