From: Nicholas Frechette <nicholas.gravel-frechette@...>
Date: 2006-10-15T22:18:36+09:00
Subject: File is a special class?

Hi, I'm currently working on a side project which has me store binary 
content in memory.
In order to make it's use as transparent as possible, i overloaded the 
'require' method to search as well in the memory and this works fine at 
the moment. In the same line of thought, I tried changing the way 
File.new works to return a StringIO object pointing to my binary data in 
memory instead of an ordinary IO object... However, i ran into an 
interesting problem. Consider the following code:

class File
    alias_method :old_new, :initialize
   
    def initialize(*args)
        if args[0] == 'a.txt'
            # Do not return a file object, return say, a Hash
            Hash.new
        else
            old_new(*args)
        end
    end
end

o = File.new('a.txt')
puts "Object is of class: #{o.class}"

This outputs:
Object is of class: File

Obviously. Now, looking further for alternatives, i tried to overload 
Class.new. Consider the following code:
class Foo
end

class Bar
end

class Class
    alias oldNew  new
    def new(*args)
        print "Creating a new ", self.name, "\n"
        if self.name == 'File'
            require 'stringio'
            StringIO.new('This is a string!','r')
        elsif self.name == 'Foo'
            Bar.new
        else
            oldNew(*args)
        end
    end
end

d = Foo.new
puts "Should be type Foo and is: #{d.class}"
n = File.new('lol.rb','r')
puts "Should be type StringIO and is: #{n.class}"
puts "Content is: #{n.read}"

With a file named lol.rb in my path with the single line of content: 
"Hello", this outputted:
Creating a new Foo
Creating a new Bar
Should be type Foo and is: Bar
Should be type StringIO and is: File
Content is: Hello

==========================
Two things here:
Class.new is working as expected with Foo, returning a Bar object. But, 
when File.new is called, Class.new is not called as it was for Foo.new!

Any thoughts/help please? I have ran out of ideas... An obvious solution 
is to use a different constructor that is not File.new but that would 
make it not very elegant.

Thanks and regards.
Nicholas