Rails - Adding Custom Fields at runtime in ActiveRecord

Question

You know how some bug trackers (and other software) allow you to add custom fields?

Typically this is done with a data structure that looks something like this:

Answer 1

If your intention is to have your FieldDefinition records belonging to different models (for example, a column item_id that points to either a SqueekyToyItem or a BalloonItem) then what you want is a polymorphic association.

It basically allows you to have an item_type column (beside your item_id column), which then specifies the actual type of item it points to.

There's a heading “Polymorphic associations” in the documentation for ActiveRecord::Associations::ClassMethods.