Using module_eval in the context of a wrapper module is one way to go. (I know you said no eval, but load/require end up eval-ing, anyway. I guess you could do something with $SAFE if you are worried about mischief.)
This has gotten so common for me that I put it in a small lib: http://redshift.sourceforge.net/script\. Here's a way of using it for what you want to do:
--- program.rb ---
require 'script'
files = [ "dog.rb", "cat.rb" ]
files.each do |file|
animal_wrapper = Script.load(file)
# animal_wrapper is a Module in whose context the top-level
# constants and methods are defined.
p animal_wrapper.main_file # should be same as the file local var
p animal_wrapper::CLASS # top-level constant in the script
p animal_wrapper.make_animal # top-level meth in the script
end
--- dog.rb ---
class Dog
def initialize name
@name = name
end
end
CLASS = Dog
def make_animal
Dog.new "Rover"
end
--- cat.rb ---
class Dog
def initialize name
@name = name
end
end
CLASS = Dog
def make_animal
Dog.new "Rover"
end
--- output of program.rb ---
"/home/vjoel/tmp/script-example/dog.rb"
#<Script:0x401c4e3c>::Dog
#<#<Script:0x401c4e3c>:
0x401c4964 @name="Rover">
"/home/vjoel/tmp/script-example/cat.rb"
#<Script:0x401c4928>::Cat
#<#<Script:0x401c4928>:
0x401c4450 @name="Fuzzy">
···
On Mon, 26 Jul 2004, Daniel Cremer wrote:
Hi,
Is there a solution to do code introspection rather than introspection
at the level of the Module/Object ? I can't figure out if I'm looking
for something that isn't there in Ruby since I've been reading C# code
or if I'm missing something. Let me explain my problem.
I would like to load ruby source files and dynamically create objects
from classes located inside these sources. It's one class/object per
source file and I can make it so that a string from a configuration
file holds the name of the class. However I can't figure out a good
way to use that string to get to the class in the source file.
I could use eval but am really uncomfortable with that for obvious
reasons (people keep saying it's evil so I don't play with him). The
other solution I came up with was to add a method in the same source
but outside the class to return the desired object:
--------------source file---------
class MyNewClass
...
end
def create_loaded_class()
return MyNewClass.new()
end
---------------------------------
Then as I require the source files I can successively invoke the
create_loaded_class method. This works but can get quite messy as
there are a lot of things to consider if you need to reload sources
and create new objects etc.
Please tell me I'm missing something obvious :).
--------
(You might want Dog and Cat to inherit from some base class that has a self.to_s method to avoid the hex junk.)
You could simplify the picture by defining the _same_ class in each script file:
class Animal
def initialize;...;end
end
and then you can reference it by
animal_wrapper::Animal.new
in your main program. The fact that dog.rb and cat.rb are loaded into different wrapper contexts keeps these classes distinct, even though their names appear the same.