One-to-one or one-to-many association

rubyonrails-talk
1

Hi,

I am creating a stock control application. I have a table called "equipment_type" that stores a general description of a piece of equipment. This could be for instance: Canon 60D DSLR camera. I also have an table called "equipment" that stores all the equipment we have with their serial numbers. There may be many Canon 60Ds and they should refer to the "equipment_type" table for their description. Is this a one-to-one association, because they have only one description. Or is this a one-to-many, because one "equipment_type" is related to many "equipment"

Thanks for your help

2

because, as you already mentioned, one "equipment_type" is referenced by many "equipment".

In Rails perspective, they can be associated like this: equipment belongs_to equipment_type equipment_type has_many equipment

Hope it would be help.

3

If it were one to one then there could only be one equipment object for each type, that is what one to one means. Have a look at the Rails Guide on ActiveRecord Associations for a good introduction to the association types.

I would avoid the use of the word equipment for the table name. It does not read well. Normally the table name should be the plural of the objects in the table. equipment_item might be better, then you can have one equipment items or two equipment_items.

Colin

4

Thanks very much for your reply. I now understand it has to be a one- to-many relation. Also you are right about the name. It caused me much confusion and I have changed it to something that pluralizes much better.