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comp.lang.ruby

class::new :: --> NUBY

Chinna Karuppan

3/19/2008 4:00:00 PM

Hi,
I was trying to redefine new in my class..like this..


class KK
alias oldnew new
def new
yield if block_given?
oldnew
end
end
NameError: undefined method `new' for class `KK'

why is saying no 'new' method....I don't understand.
because I can say KK.new after I define the class which means the method
is there in the class hierarchy and I should be able to override its
implementation....

THnks
Chinna
--
Posted via http://www.ruby-....
4 Answers

Mark Bush

3/19/2008 4:38:00 PM

0

Chinna Karuppan wrote:
> class KK
> alias oldnew new

> NameError: undefined method `new' for class `KK'

You are trying to alias the *instance* method #new which doesn't exist.
#new is a *class* method so you need to alias it in the metaclass.
Something like:

class KK
end

class << KK
alias_method :oldnew, :new
def new
yield if block_given?
oldnew
end
end

(You need the class to exist first before you access the metaclass.)

--
Posted via http://www.ruby-....

Ken Bloom

3/19/2008 5:08:00 PM

0

On Wed, 19 Mar 2008 11:00:28 -0500, Chinna Karuppan wrote:

> Hi,
> I was trying to redefine new in my class..like this..
>
>
> class KK
> alias oldnew new
> def new
> yield if block_given?
> oldnew
> end
> end
> NameError: undefined method `new' for class `KK'
>
> why is saying no 'new' method....I don't understand. because I can say
> KK.new after I define the class which means the method is there in the
> class hierarchy and I should be able to override its implementation....
>
> THnks
> Chinna

I think you want to define the constructor for class KK as:

class KK
def initialize
yield if block_given
super
end
end

Does this do what you're trying to accomplish?

--
Ken (Chanoch) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu...

WujcioL

3/19/2008 5:24:00 PM

0

[Note: parts of this message were removed to make it a legal post.]

Try this code:
class KK
def new
yield if block_given?
super
end
end

2008/3/19, Chinna Karuppan <chinnakaruppan@gmail.com>:
>
> Hi,
> I was trying to redefine new in my class..like this..
>
>
> class KK
> alias oldnew new
> def new
> yield if block_given?
> oldnew
> end
> end
> NameError: undefined method `new' for class `KK'
>
> why is saying no 'new' method....I don't understand.
> because I can say KK.new after I define the class which means the method
> is there in the class hierarchy and I should be able to override its
> implementation....
>
> THnks
> Chinna
>
> --
> Posted via http://www.ruby-....
>
>

Ken Bloom

3/19/2008 7:08:00 PM

0

On Wed, 19 Mar 2008 12:23:58 -0500, Mateusz Tybura wrote:

> [Note: parts of this message were removed to make it a legal post.]
>
> Try this code:
> class KK
> def new
> yield if block_given?
> super
> end
> end

This won't work, because it operates on an instance method named new.

--Ken

--
Ken (Chanoch) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu...