How to Get the Parent's Class Name in Ruby

How do I get the parent's class name in Ruby

class A
end

class B < A
end

B.superclass # => A
B.superclass.name # => "A"

Rails: Get the Class Name of a Child Class in a Parent Class Method

I don't think you can avoid having some knowledge of the specific subclass if you want the type set correctly, however you could streamline the code so there is far less code duplication. Something like:

class Vote
  def self.cast_vote_of_type(params, subtype)
     ....first_or_create(value: value, type: subtype)
  end
end

class Tag::Vote
  def self.cast_vote(params)
    cast_vote_of_type(params, self.class.name)
  end
end

How to get Child class in inherited parent method in Ruby?

In a class method like your find_by_id:

class ModelBase  
  def self.find_by_id(id)
    p self.class.name
  end
end

self is the class itself (so self.class is Class) so you want to look at self.name:

class ModelBase  
  def self.find_by_id(id)
    p name
  end
end

Look up all descendants of a class in Ruby

Here is an example:

class Parent
  def self.descendants
    ObjectSpace.each_object(Class).select { |klass| klass < self }
  end
end

class Child < Parent
end

class GrandChild < Child
end

puts Parent.descendants
puts Child.descendants

puts Parent.descendants gives you:

GrandChild
Child

puts Child.descendants gives you:

GrandChild

Class Method to 'Know' Class Name in Ruby?

A Class Method is a method where the CLASS is the receiver, so to find the object upon which the method is invoked (what you appear to be trying to do here) simply inspect the value of self.

class Parent
  def self.whoami
    self
  end
end

class Child < Parent
end

puts Parent.whoami #=> Parent
puts Child.whoami #=> Child

Get Ruby pure class name without parent name, any direct method for it?

Classes don't really have "names" in Ruby. A class is an object like any other object, it gets assigned to variables like any other object. A class doesn't have a name, just like a number or a string doesn't have a name.

Take this example:

foo = Class.new

Bar = foo
Baz = foo

Bar = nil
remove_const :Bar

What should the "name" of the class be in this example?

Well, there is a method called name in the Module class. What it does is the following: if the class object has been assigned to a constant for the first time, the name of that constant (note that even that is a fuzzy concept!) becomes the name of the class, otherwise the name will just be nil.

Expanding on the example above:

foo = Class.new

foo.name
# => nil

Bar = foo

foo.name
# => 'Bar'
Bar.name
# => 'Bar'

Baz = foo

Baz.name
# => 'Bar'

Bar = nil
remove_const :Bar

foo.name
# => 'Bar'

Here's another example:

foo = Class.new
Bar = foo
Baz = foo

class Baz
  class Quux; end

  Xyzzy = Quux
end

foo::Xyzzy.name
# => 'Bar::Quux'

Note that even though Quux is defined inside Baz and accessed via foo::Xyzzy it still prints Bar::Quux as its name.

Also, two different classes can have the same name:

Foo = Class.new

Bar = Foo

Foo = nil
remove_const :Foo

Foo = Class.new

Baz = Foo

Foo = nil
remove_const :Foo

Bar.name
# => Foo

Baz.name
# => Foo

Bar == Baz
# => false

The "name" of a class is simply a debugging help for human readers, you should never use it for anything else, and never use it programmatically (or even depend on a specific structure of the string).

How can I determine the child class name from abstract parent class in Ruby

You can try using the inherited hook:

class BaseClass
  def self.inherited(child_class)
    child_class.class_eval do
      belongs_to :parent, :class_name => child_class.name
    end
    super
  end
end