Comments on Electric Sheep Blog: Loading classes from strings in Ruby

Sidu and Travis: thanks for clarifying this. I am...

2010-08-31T00:23:04.210+05:30

Sidu and Travis: thanks for clarifying this. I am able to use Travis' way to retrieve a class nested within a module.

I haven't benchmarked this, but you can also d...

2010-06-14T23:16:56.792+05:30

I haven't benchmarked this, but you can also do:

Module.const_get("ModuleName").const_get("ClassName")

I added the Rails 2.3.5 constantize to the benchma...

2010-03-22T07:49:00.428+05:30

I added the Rails 2.3.5 constantize to the benchmarks above, and in my results it's over 7 times slower than the "simple invocation" and 4 times slower than const_get.

Yes, I have!!! But #constantize is a Rails (active...

2009-10-26T01:59:06.854+05:30

Yes, I have!!! But #constantize is a Rails (activesupport) extension, so without Rails, no #constantize.

Have you tried "MyClassName".constantize...

2009-10-25T09:04:29.211+05:30

Have you tried "MyClassName".constantize.new ???

If you have a string containing a potential class ...

2009-06-04T08:58:07.671+05:30

If you have a string containing a potential class name and you're not sure if its formatted correctly for whatever reason before you use 'eval' or 'Kernel.const_get', you can use 'Kernel.subclasses_of(ActiveRecord::Base).member?(YourClass)' to check if it exists so you don't get a 'LoadError: ./activesupport-2.3.2/lib/active_support/dependencies.rb:426:in `load_missing_constant''

Not exactly faster, but another approach is to ite...

2008-04-17T04:56:00.000+05:30

Not exactly faster, but another approach is to iterate through the ObjectSpace collection, and instantiate the matching class:

require 'my_package/my_class'

class Factory
def self.get_object(o)
ObjectSpace.each_object(Class) do |c|
return c.new() if c.name.eql?(o)
end
return nil
end
end

#usage
require 'factory'
o = Factory.get_object("MyPackage::MyClass")

I've been experimenting with JRuby and found that ...

2008-02-07T07:38:00.000+05:30

I've been experimenting with JRuby and found that using const_get is just unreliable, while eval works fine. For example, a java class com.foo.bar.Baz is represented as Java::FooBar::Baz. If you do const_get on Java::FooBar, you get a string "Java::FooBarConst_get". It appears that these Java package modules must define method_missing to just concatenate the method name to the module name. I haven't investigated further.

Anyway, using eval works fine.