Styjun

I can't figure out how to initialize a class from a parent class variable. I'm trying to accomplish this:

x = A::B.new('my string')
myObject = x::C.new(**params)

and the program I'm calling is organized similar to:

module A
 ...<stuff>...
 class B
 ...<stuff>....
 class C < B
 ...<stuff>...
 end
 end
end

I want to initialize the class C after initializing the parent class B. That way, I can have access to class B's variables and methods from class C.

When I try to execute my program, I get:

"#<A::B:0x...............>" is not a class/module (TypeError)

Can anyone point me in the right direction for initializing nested classes like this?

You can't construct an instance from an instance - the whole module hierarchy is only applicable to modules and classes. Since x is neither, the parser has no idea what :: is supposed to do.

The idea behind nested classes is that they are namespaced within the parent class, no more, no less. In effect, class B acts like a module prefix to class C, but there's no inherent relationship between them (by being nested alone; you do inherit C from B in your example, which is what gives you the relationship), and certainly not between an instance of B and the class C

Instead, I would recommend constructing a C directly with 'my string', then calling #super in the initialize method, like so:

myObject = A::B::C.new('my string', **params)

and in the implementation:

module A
 class B
 def initialize(some_string)
 @some_string = some_string
 end
 class C < B
 def initialize(str, params)
 super(str)
 ...
 end
 end
 end
end

As the error message suggests, the namespace operator :: can only be applied to a class/module. If x were the class A::B, then x::C should work. It does not make sense to apply ::C on an instance of A::B.

You need to apply the :: to x's class, not x itself. So you just need a call to the class method:

x = A::B.new('my string')
myObject = x.class::C.new(**params)

For example, this sort of thing:

module A
 class B
 class C
 end
 end
end

pancakes = A::B.new
eggs = pancakes.class::C.new

puts pancakes.inspect
puts eggs.inspect

gives you something like this:

#<A::B:0x007faea90b6a58>
#<A::B::C:0x007faea90b6a30>