RoR Create method, which return list of instance methods

I'm stuck with two things. This is structure of my file.

class Person
  ...

  def self.class_name (object)
     object.class.name
  end

end

class Worker < Person
  ... 
end

class Client < Person
  ...
end

c = Client.new("1", "2", "3", "4")
Person.class_name(c)

I would like to create method, where as argument i can put some object and it will detect, what class is it and return me list of all instance methods, which don't require any argument. Later i need to somehow use all these methods.

I have found this:

testObject.class.name 
#Returns name of class as a string

Class.instance_methods(false)
#Returns list of instance method, which were defined in Class

First problem, is that i don't understand why i can't make something like

className = testObject.class.name 
className.instance_methods(false)

I suppose, that's becouse i got just class name, as a sting, not a real reference to the class. I have even created simple class_name method, which returns correct name of class, but i'm wondering how i can use instance_methods(false), once i have this name. Also is there some option to choose only methods, which don't require any argument?