Overriding object instantiation?

rubyonrails-talk
1

Hi all,

ROR newbie coming from a PHP background here.

I have a model that inherits from ActiveRecord::Base. I would like to extend that into two further models, to separate functionality from each other. Basically:

class Person < ActiveRecord::Base   attr_accessible :gender end

class Male < Person

end

class Female < Person

end

How can I write a method within Person that will detect what gender has been defined and return the proper object based on it?

I'm thinking something like...

def self.new   gender_class = self.gender == 'Female' ? 'Female' : 'Male'   eval(gender_class).new end

In that version, though, "self.gender" isn't recognized. I'm sure I'm missing something really basic, but can someone point out what it is?

Thanks!

2

new is a class method, but gender is an instance method. Apart from that I'm not sure what you're trying to do? Do you know that Active Record can handle STI for you ?

Fred

3

moonshadow wrote:

Hi all,

ROR newbie coming from a PHP background here.

I have a model that inherits from ActiveRecord::Base. I would like to extend that into two further models, to separate functionality from each other. Basically:

class Person < ActiveRecord::Base   attr_accessible :gender end

class Male < Person

end

class Female < Person

end

How can I write a method within Person that will detect what gender has been defined and return the proper object based on it?

You probably want to use single-table inheritance (STI) for this. Read the ActiveRecord docs on this point.

Best,

4

if you put a field called type in the table of the base class AR will automaticly save to the correct class, in fact from that moment on everything will behave as is you had 2 models, no need for more configuration.

5

moonshadow wrote:

def self.new   gender_class = self.gender == 'Female' ? 'Female' : 'Male'   eval(gender_class).new end

Really, look into how ActiveRecord handles STI by using the type column. It will handle all of this for you.

That said, the way to do something when an object is created is with:

def initialize   # do some stuff, and you should probably call super   super end