Ruby - Name Resolution Using a Variable

Question

Is it possible to do something like this in Ruby:

var_1 = Module
var_2 = NestedModule

object = ::var_1::var_2::SomeObject.new # class resolves to ::Module::NestedModule::SomeObject

Though the above code does not work in Ruby, is there any alternative way to do this or is this not possible?

Answer 1

First off, NestedModule is a bad name for a variable, in fact, it is actively misleading: the module isn't nested (there are no nested modules in Ruby), it's the constant that is nested.

In fact, that's precisely the confusion that leads to this question.

So, the constant NestedModule is nested inside the module referenced by the constant Module , which, however, because of your first line, is also accessible through the local variable var_1 . (Remember, Module s are objects just like any other object!):

var_1 = Module

To get a reference to NestedModule in var_2 , you can do:

var_2 = var_1::NestedModule

And lastly, to get a reference to SomeObject , you can do:

var_2::SomeObject.new

Answer 2

You could do something like this:

klass  = Object.const_get("::#{var_1}::#{var_2}::Object")
object = klass.new