Find classes available in a Module

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?

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最佳答案

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}
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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]**
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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

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