From: Stefano Crocco <stefano.crocco@...>
Date: 2007-02-26T04:23:55+09:00
Subject: Re: Type of class

Alle domenica 25 febbraio 2007, J. mp ha scritto:
> Hi
> How do I know if a variable is an instace of a given class
>
> I have a method that returns a String or an Array and I have to now
> outside if the returned object is and String or an Array.
>
> Is beacuse this :
>      # File vendor/rails/activerecord/lib/active_record/validations.rb,
> line 100
> 100:     def on(attribute)
> 101:       errors = @errors[attribute.to_s]
> 102:       return nil if errors.nil?
> 103:       errors.size == 1 ? errors.first : errors
> 104:     end
>
>
> How do I know that call on method on returned and array or an string?
>
> Thanks

The is_a? method tells whether the receiver is an instance of the class passed 
as argument or of one of its derived class:

a=[1,2,3]

a.is_a?(Array)
=> true
a.is_a?(String)
=> false

If you need to know whether an object is an instance of exactly a specific 
class (not of derived class), you can use the == on the class:

class A
end

class B < A
end

b=B.new
b.is_a?(A)
=> true
b.class==A
=> false
b.class==B
=> true

I hope this helps

Stefano