Best way to enumerate STI subclasses

Rails
1

Hello,

Following the AWDWR STI example (People, Employee, Manager, etc). If I
want to present a list of potential subclasses to add, and I plan on
extending the list of subclasses over time, what is the best way to
generate the subclass list?

For example, should I create a YAML file and parse that? Create a table
in the db and read that in? Or is there some other way to get that list
from ActiveRecord?

Thanks,
Ryan G.

2

Ryan G. wrote:

from ActiveRecord?

Thanks,
Ryan G.

See this discussion:
http://groups.google.co.uk/group/rubyonrails-talk/browse_thread/thread/475260e21167de9a/51721d1d1d9c9c50?lnk=st&q=inverse+base_class&rnum=1&hl=en#51721d1d1d9c9c50

Alternatively you could just use a constant defined in the base class,
something like
SUBCLASSES = [Employee, Manager, Slave…]
and then refer to it using Person::SUBCLASSES
or perhaps prettier define a method in the base class
def subclasses
[Employee, Manager, Slave…]
end

and then refer to it using Person.subclasses

3

Alternatively you could just use a constant defined in the base class,
something like
SUBCLASSES = [Employee, Manager, Slave…]
and then refer to it using Person::SUBCLASSES
or perhaps prettier define a method in the base class
def subclasses
[Employee, Manager, Slave…]
end

and then refer to it using Person.subclasses

OBJECT already supports sub_classes method. you can use it on any model
without defining hard-coded list.

4

Elad M. - Creopolis.com wrote:

and then refer to it using Person.subclasses

OBJECT already supports sub_classes method. you can use it on any model
without defining hard-coded list.

If you look at the referenced thread you’ll see there are some
performance downsides to using Object#subclasses_of, which I think is
what you’re referring to…