Find classes available in a Module
RubyMetaprogrammingRuby Problem Overview
I have a module MyModule
. I dynamically load classes into it. How can I get a list of the classes defined within its namespace?
Example:
def load_plugins
Dir.glob(File.dirname(__FILE__) + '/plugins/*.rb') do |f|
MyModule.class_eval File.read(f)
end
# now how can I find the new classes I've loaded into MyModule?
end
I should say that each f
contains something like "class Foo; end".
You can also think of it like this: in Rails, how could I programatically find all classes defined within the ActiveRecord module?
Ruby Solutions
Solution 1 - Ruby
Classes are accessed through constants. Classes defined within a module are listed as constants in that module. So you just need to choose the constants that refer to classes.
MyModule.constants.select {|c| MyModule.const_get(c).is_a? Class}
Solution 2 - Ruby
If you're on rails, you need to access the constants first for them to show up, because they're lazyly loaded.
MyModule::NotAClass = "not a class"
MyModule.constants => [:NotAClass]
MyModule::AClass => :AClass # Access class for it to be autoloaded
MyModule.constants => [:AClass, :NotAClass]
# Now, select the constants which are class instances
MyModule.constants
.map(&MyModule.method(:const_get))
.select { |constant| constant.is_a? Class}
=> [MyModule::AClass]**
Solution 3 - Ruby
If you'd like to get all classes in a module recursively, you can do something like
def get_classes(mod)
mod.constants.map do |c|
const = mod.const_get(c)
if const.is_a? Class
const
elsif const.is_a? Module
get_classes(const)
else
next
end
end.flatten
end
Then, given some module structure like:
module MyModule
module Submodule1
class Class1
end
end
module Submodule2
class Class2
end
end
end
the output looks like:
puts get_classes(MyModule)
# => MyModule::Submodule1::Class1
# => MyModule::Submodule2::Class2