I have two objects, a CarOffer and a Car. A CarOffer is composed of various attributes, one of which references a Car. In other words, I can have multiple CarOffers, multiple Cars, but there is one and only one Car per CarOffer. A Car can be present in multiple CarOffers. Deleting a CarOffer should not delete the car it references, and deleting a Car should not be possible unless all CarOffers referencing it have also been deleted.
Usually, I would just have added a carId attribute to CarOffer, but from the gorm documentation I feel I should use the power of Gorm to add a Car Object to CarOffer, instead of just its id.
However I'm a bit lost, I feel neither 'belongsTo' nor 'hasOne' really map to what I want.
Besides, how would I go to create a new CarOffer? I would expect to be able to do
new CarOffer(carId: 123).save()
but instead I feel I must do:
new CarOffer(car: Car.get(123)).save()
Does that not create one extra request?
I feel neither 'belongsTo' nor 'hasOne' really map to what I want.
You don't want belongsTo because that will cause deletes to be cascaded and you said you didn't want that ("Deleting a CarOffer should not delete the car it references").
You could use a hasOne or not, that will affect which table has the foreign key in it.
If you don't want to use the carId approach, you can do something like this:
class CarOffer {
String attribute1
int attribute 2
// etc...
Car car
}
class Car {
String attribute1
// etc...
// There could be, but does not need to be
// any mention of CarOffer in this class
}
...how would I go to create a new CarOffer?
It depends on details in your app that you haven't mentioned but you can do some thing like this...
Car c = // ...
CarOffer co = new CarOffer(attribute1: 'something', attribute2: 2112, car: c)