Class X; class << X : what is this idiom?

ruby-talk
1

In article a6e48b6b.0306181426.62e8d934@posting.google.com,

I have seen this idiom quite a few times, and have not figured out
what it does (looking at the pickaxe book). Could someone help
enlighten me?

[My guess is that it creates a customized meta-class that X is an
instance of; am I guessing right?]

I think that’s a pretty close guess…

Here’s a section from the Rubygarden Wiki:

“<<” also creates a new class based on a particular object.
These object-specific classes are called ‘singleton classes’.
In the example below, only the Car object referred to by
“camaro” will have the method “has_flames?”.

         camaro = Car.new
         class << camaro
           def has_flames?
             true
           end
         end

See also TheScaryDoor on the wiki:

Phil

···

you CAN teach an old dog … itsme213@hotmail.com wrote:

2

and:

Regards,

Brian.

···

On Fri, Jun 20, 2003 at 10:10:49AM +0900, Phil Tomson wrote:

In article a6e48b6b.0306181426.62e8d934@posting.google.com,
you CAN teach an old dog … itsme213@hotmail.com wrote:

I have seen this idiom quite a few times, and have not figured out
what it does (looking at the pickaxe book). Could someone help
enlighten me?

[My guess is that it creates a customized meta-class that X is an
instance of; am I guessing right?]

I think that’s a pretty close guess…

Here’s a section from the Rubygarden Wiki:
http://www.rubygarden.org/ruby?FunnySymbolsInCode

“<<” also creates a new class based on a particular object.
These object-specific classes are called ‘singleton classes’.
In the example below, only the Car object referred to by
“camaro” will have the method “has_flames?”.

         camaro = Car.new
         class << camaro
           def has_flames?
             true
           end
         end

See also TheScaryDoor on the wiki:
http://www.rubygarden.org/ruby?TheScaryDoor