# Identfying classes in a file dynamically
**URL:** https://rubytalk.org/t/identfying-classes-in-a-file-dynamically/26560
**Category:** ruby-talk
**Created:** [10 April 2006 22:21 UTC](https://rubytalk.org/t/identfying-classes-in-a-file-dynamically/26560 "2006-04-10T22:21:54Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@Navya\_Amerineni](https://rubytalk.org/u/Navya_Amerineni)
#### Post date: [10 April 2006 22:21 UTC](https://rubytalk.org/t/identfying-classes-in-a-file-dynamically/26560/1 "2006-04-10T22:21:54Z")
Hi,
I was trying to identify the classes in a give file at the run time. the following is the code i used.
sc, ec = [], []
ObjectSpace.each\_object(Class) { |c| sc \<\< c }
require 'Roman.rb'
ObjectSpace.each\_object(Class) { |c| ec \<\< c }
new\_classes = ec - sc
puts new\_classes
sc, ec = [], []
ObjectSpace.each\_object(Class) { |c| sc \<\< c }
require 'Roman1.rb'
ObjectSpace.each\_object(Class) { |c| ec \<\< c }
new\_classes = ec - sc
puts new\_classes
Both roman.rb and roman1.rb has the same class Roman.
the first time i print the new\_classes i can see the Roman class in the output but the second one does not print because the class Roman is arleady read previously.
is there a way i can over come this problem and identify the Roman class twice.
Thanks,
Navya.
> **···**
>
> ---------------------------------
> New Yahoo! Messenger with Voice. Call regular phones from your PC and save big.
---
### Author:  [@Joel\_VanderWerf1](https://rubytalk.org/u/Joel_VanderWerf1)
#### Post date: [11 April 2006 01:27 UTC](https://rubytalk.org/t/identfying-classes-in-a-file-dynamically/26560/2 "2006-04-11T01:27:35Z")
Navya Amerineni wrote:
> Hi,
>
> I was trying to identify the classes in a give file at the run time. the following is the code i used.
> sc, ec = ,
> ObjectSpace.each\_object(Class) { |c| sc \<\< c }
> require 'Roman.rb'
> ObjectSpace.each\_object(Class) { |c| ec \<\< c }
> new\_classes = ec - sc
> puts new\_classes
> sc, ec = ,
> ObjectSpace.each\_object(Class) { |c| sc \<\< c }
> require 'Roman1.rb'
> ObjectSpace.each\_object(Class) { |c| ec \<\< c }
> new\_classes = ec - sc
> puts new\_classes
>
> Both roman.rb and roman1.rb has the same class Roman.
> the first time i print the new\_classes i can see the Roman class in the output but the second one does not print because the class Roman is arleady read previously.
>
> is there a way i can over come this problem and identify the Roman class twice.
One way is to wrap the file in a module, so that the constants defined
in it will not collide with other constants.
file = "some/file"
m = Module.new
m.module\_eval(IO.read(file), File.expand\_path(file))
p m.constants
But then the Roman module won't be available except as m::Roman. To fix
this, you could include m into any class or module that needs to use Roman.
> **···**
>
> --
> vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
---
### Author:  [@Zach\_Dennis1](https://rubytalk.org/u/Zach_Dennis1)
#### Post date: [11 April 2006 13:56 UTC](https://rubytalk.org/t/identfying-classes-in-a-file-dynamically/26560/3 "2006-04-11T13:56:14Z")
Navya Amerineni wrote:
> Hi,
>
> I was trying to identify the classes in a give file at the run time. the following is the code i used.
> sc, ec = ,
> ObjectSpace.each\_object(Class) { |c| sc \<\< c }
> require 'Roman.rb'
> ObjectSpace.each\_object(Class) { |c| ec \<\< c }
> new\_classes = ec - sc
> puts new\_classes
> sc, ec = ,
> ObjectSpace.each\_object(Class) { |c| sc \<\< c }
> require 'Roman1.rb'
> ObjectSpace.each\_object(Class) { |c| ec \<\< c }
> new\_classes = ec - sc
> puts new\_classes
>
> Both roman.rb and roman1.rb has the same class Roman.
> the first time i print the new\_classes i can see the Roman class in the output but the second one does not print because the class Roman is arleady read previously.
>
> is there a way i can over come this problem and identify the Roman class twice.
Way #1, store the new classes in a hash. This way you won't be overriding any classes you've previously loaded.
Way #2, use one array to store new classes, and then each time you compute the "new\_classes" after you load a file, merge those
into your one authoriatize array. This way you won't be overriding any classes you've previously loaded.
Way #3, pass a string into a new ruby process which loads the files and outputs the new classes. Read these in and then use Way #1
or Way #2 to store the classes. This is a bit hackish, but it works and it leaves your toplevel ruby process namespace alone.
Here is the idea of Way #3
str =\<\<-'EOT'
def count\_classes( arg )
arr =
ObjectSpace.each\_object( arg ){ |c| arr \<\< c }
arr
end
orig\_classes = count\_classes( Class )
require "load"
new\_classes = count\_classes( Class ) - orig\_classes
puts new\_classes.join( "\n" )
EOT
child = IO.popen( "ruby -e '#{str}'", "r" )
new\_classes = child.readlines.map!{ |s| s.chomp! }
puts new\_classes
Zach
---
### Author:  [@David\_A\_Black3](https://rubytalk.org/u/David_A_Black3)
#### Post date: [11 April 2006 02:12 UTC](https://rubytalk.org/t/identfying-classes-in-a-file-dynamically/26560/4 "2006-04-11T02:12:36Z")
Hi --
> **···**
>
> On Tue, 11 Apr 2006, Joel VanderWerf wrote:
>
> > Navya Amerineni wrote:
> >
> > > Hi,
> > >
> > > I was trying to identify the classes in a give file at the run time. the following is the code i used.
> > > sc, ec = ,
> > > ObjectSpace.each\_object(Class) { |c| sc \<\< c }
> > > require 'Roman.rb'
> > > ObjectSpace.each\_object(Class) { |c| ec \<\< c }
> > > new\_classes = ec - sc
> > > puts new\_classes
> > > sc, ec = ,
> > > ObjectSpace.each\_object(Class) { |c| sc \<\< c }
> > > require 'Roman1.rb'
> > > ObjectSpace.each\_object(Class) { |c| ec \<\< c }
> > > new\_classes = ec - sc
> > > puts new\_classes
> > >
> > > Both roman.rb and roman1.rb has the same class Roman.
> > > the first time i print the new\_classes i can see the Roman class in the output but the second one does not print because the class Roman is arleady read previously.
> > >
> > > is there a way i can over come this problem and identify the Roman class twice.
> >
> > One way is to wrap the file in a module, so that the constants defined
> > in it will not collide with other constants.
> >
> > file = "some/file"
> > m = Module.new
> > m.module\_eval(IO.read(file), File.expand\_path(file))
> > p m.constants
> >
> > But then the Roman module won't be available except as m::Roman. To fix
> > this, you could include m into any class or module that needs to use Roman.
>
> Also I think that if the read-in file uses the ::Const construct,
> those classes won't get counted.
>
> David
>
> --
> David A. Black (dblack@wobblini.net)
> Ruby Power and Light, LLC ([http://www.rubypowerandlight.com](http://www.rubypowerandlight.com))
>
> "Ruby for Rails" coming in PDF April 15, and in paper May 5!
>
> > **[Ruby for Rails](https://www.manning.com/books/ruby-for-rails)**
> >
> > NEWER EDITION AVAILABLE
> >
> > The Well-Grounded Rubyist, Second Edition is now available. An eBook of the previous edition, The Well-Grounded Rubyist is included at no additional cost when you buy the revised edition!
> >
> >
> > Ruby for Rails helps Rails...
---
### Author:  [@Joel\_VanderWerf1](https://rubytalk.org/u/Joel_VanderWerf1)
#### Post date: [11 April 2006 02:21 UTC](https://rubytalk.org/t/identfying-classes-in-a-file-dynamically/26560/5 "2006-04-11T02:21:03Z")
dblack@wobblini.net wrote:
...
> Also I think that if the read-in file uses the ::Const construct,
> those classes won't get counted.
You mean like this:
$ cat t.rb
class ::Foo
end
$ ruby -e 'load "t.rb"; p Foo'
Foo
$ ruby -e 'load "t.rb"; ObjectSpace.each\_object(Class) {|c| p c if
c.name == "Foo"}'
Foo
So it doesn't look like that works, unless I'm misunderstanding...
> **···**
>
> --
> vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
---
### Author:  [@David\_A\_Black3](https://rubytalk.org/u/David_A_Black3)
#### Post date: [11 April 2006 02:47 UTC](https://rubytalk.org/t/identfying-classes-in-a-file-dynamically/26560/6 "2006-04-11T02:47:09Z")
Hi --
> **···**
>
> On Tue, 11 Apr 2006, Joel VanderWerf wrote:
>
> > dblack@wobblini.net wrote:
> > ...
> >
> > > Also I think that if the read-in file uses the ::Const construct,
> > > those classes won't get counted.
> >
> > You mean like this:
> >
> > $ cat t.rb
> > class ::Foo
> > end
> > $ ruby -e 'load "t.rb"; p Foo'
> > Foo
> > $ ruby -e 'load "t.rb"; ObjectSpace.each\_object(Class) {|c| p c if
> > c.name == "Foo"}'
> > Foo
> >
> > So it doesn't look like that works, unless I'm misunderstanding...
>
> Yes, that's what I meant; if you have ::Foo in your file, then you
> won't get a Foo class in the module you wrap in, so you won't get the
> right count of modules in the file.
>
> David
>
> --
> David A. Black (dblack@wobblini.net)
> Ruby Power and Light, LLC ([http://www.rubypowerandlight.com](http://www.rubypowerandlight.com))
>
> "Ruby for Rails" coming in PDF April 15, and in paper May 5!
>
> > **[Ruby for Rails](https://www.manning.com/books/ruby-for-rails)**
> >
> > NEWER EDITION AVAILABLE
> >
> > The Well-Grounded Rubyist, Second Edition is now available. An eBook of the previous edition, The Well-Grounded Rubyist is included at no additional cost when you buy the revised edition!
> >
> >
> > Ruby for Rails helps Rails...
---
### Author:  [@Joel\_VanderWerf1](https://rubytalk.org/u/Joel_VanderWerf1)
#### Post date: [11 April 2006 03:17 UTC](https://rubytalk.org/t/identfying-classes-in-a-file-dynamically/26560/7 "2006-04-11T03:17:05Z")
dblack@wobblini.net wrote:
> Hi --
>
> > ...
> >
> > > Also I think that if the read-in file uses the ::Const construct,
> > > those classes won't get counted.
> >
> > You mean like this:
> >
> > $ cat t.rb
> > class ::Foo
> > end
> > $ ruby -e 'load "t.rb"; p Foo'
> > Foo
> > $ ruby -e 'load "t.rb"; ObjectSpace.each\_object(Class) {|c| p c if
> > c.name == "Foo"}'
> > Foo
> >
> > So it doesn't look like that works, unless I'm misunderstanding...
>
> Yes, that's what I meant; if you have ::Foo in your file, then you
> won't get a Foo class in the module you wrap in, so you won't get the
> right count of modules in the file.
Oh, I see--I thought you meant it was a workaround, but it's actually a
limitation of the module wrapping trick. Good point.
> **···**
>
> > On Tue, 11 Apr 2006, Joel VanderWerf wrote:
> >
> > > dblack@wobblini.net wrote:
>
> --
> vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407