I’ve been struggling to get a clear and straight-forward answer on
this one, I’m hoping this time I’ll get it! I definitely have a lot
to learn still with Rails, however I do understand the problem I’m
facing and would really appreciate additional help.
o I have a model called “Task”.
o I have an abstract model called “Target”.
o I would like to relate multiple instances of subclasses of Target to
o I am not using single table inheritance.
o I would like to query the polymorphic relationship to return a mixed
result set of subclasses of Target.
o I would like to query individual instances of subclasses of Target
to obtain tasks that they are in a relationship with.
So, I figure a polymorphic many to many relationship between Tasks and
subclasses of Targets is in order. In more detail, I will be able to
do things like this in the console (and of course elsewhere):
task = Task.find(1)
[…array of all the subclasses of Target here…]
But! Assuming models “Store”, “Software”, “Office”, “Vehicle”, which
are all subclasses of “Target” exist, it would be nice to also
traverse the relationship in the other direction:
store = Store.find(1)
[…array of all the Tasks this Store is related to…]
software = Software.find(18)
[…array of all the Tasks this Software is related to…]
The database tables implied by polymorphic relationships appears to be
capable of doing this traversal. The class name is present in the
relationship table, but I see some recurring themes in trying to find
an answer which to me defeat the spirit of polymorphic relationships:
o Using my example still, people appear to want to define Store,
Software, Office, Vehicle in Task, which we can tell right away isn’t
a polymorphic relationship as it only returns one type of model.
o Similar to the last point, people still want to define Store,
Software, Office and Vehicle in Task in one way shape or form. The
important bit here is that the relationship is blind to the
subclassing. My polymorphs will initially only be interacted with as
Targets, not as their individual subclass types. Defining each
subclass in Task again starts to eat away at the purpose of the
o I see that a model for the join table might be in order, that seems
somewhat correct to me except that it adds some complexity I assumed
Rails would be willing to do away with. I plea inexperience on this
It seems to be a small hole in either rails functionality or the
collective community knowledge.
I am also maintaining this question here:
Thanks to everyone who help!