How can a polymorphic object check its own class type?

rubyonrails-talk
1

I have a polymorphic class and need to know the type from within the model (for validation).

From a controller, I can check instance[:type] to get the object's

type, but how do I access this attribute from within the model?

If I check 'type', I get a warning (and wrong value). Checking 'self.class', just says 'Class'.

Thanks, Amir

2

helzer wrote:

I have a polymorphic class and need to know the type from within the model (for validation).

>From a controller, I can check instance[:type] to get the object's type, but how do I access this attribute from within the model?

If I check 'type', I get a warning (and wrong value). Checking 'self.class', just says 'Class'.

Thanks, Amir

>

Not sure I'm quite understanding this correctly but hope this helps:

class ParentKlass < ActiveRecord::Base end

class ChildKlass < ParentKlass

  def self.class_details     puts "my class is #{self}" # self here IS the class     puts "my base_class is #{self.base_class}" # gets the base class given a class   end

  def class_details     puts "my class is #{self.class}" # we're asking for details of the instance's class     puts "my base_class is #{self.class.base_class}" # and then the base class of that class   end

end

ChildKlass.class_details # my class is ChildKlass # my base_class is ParentKlass

ChildKlass.new.class_details # my class is ChildKlass # my base_class is ParentKlass

Cheers Chris

3

Hi Chris,

I tried to do that, but it didn't work for me. My mistake was, I put that code in the parent class. So whenever this code was called, it reported the name of the parent and not the child.

Now that I've moved each case to the relevant child #{self} reports the correct class name.

And, instead of writing complex class-dependent validation in the parent class (which is inherently wrong to do), I now have simpler validation in each child.

Thanks, Amir