BasicObject

BasicObject is the parent class of all classes in Ruby. It’s an explicit blank class.

BasicObject can be used for creating object hierarchies independent of Ruby’s object hierarchy, proxy objects like the Delegator class, or other uses where namespace pollution from Ruby’s methods and classes must be avoided.

To avoid polluting BasicObject for other users an appropriately named subclass of BasicObject should be created instead of directly modifying BasicObject:

class MyObjectSystem < BasicObject
end

BasicObject does not include Kernel (for methods like puts) and BasicObject is outside of the namespace of the standard library so common classes will not be found without using a full class path.

A variety of strategies can be used to provide useful portions of the standard library to subclasses of BasicObject. A subclass could include Kernel to obtain puts, exit, etc. A custom Kernel-like module could be created and included or delegation can be used via method_missing:

class MyObjectSystem < BasicObject
  DELEGATE = [:puts, :p]

  def method_missing(name, *args, &block)
    return super unless DELEGATE.include? name
    ::Kernel.send(name, *args, &block)
  end

  def respond_to_missing?(name, include_private = false)
    DELEGATE.include?(name) or super
  end
end

Access to classes and modules from the Ruby standard library can be obtained in a BasicObject subclass by referencing the desired constant from the root like ::File or ::Enumerator. Like method_missing, const_missing can be used to delegate constant lookup to Object:

class MyObjectSystem < BasicObject
  def self.const_missing(name)
    ::Object.const_get(name)
  end
end

What’s Here

These are the methods defined for BasicObject:

• ::new

  Returns a new BasicObject instance.

• !

  Returns the boolean negation of self: true or false.

• !=

  Returns whether self and the given object are not equal.

• ==

  Returns whether self and the given object are equivalent.

• __id__

  Returns the integer object identifier for self.

• __send__

  Calls the method identified by the given symbol.

• equal?

  Returns whether self and the given object are the same object.

• instance_eval

  Evaluates the given string or block in the context of self.

• instance_exec

  Executes the given block in the context of self, passing the given arguments.

• method_missing

  Method called when an undefined method is called on self.

• singleton_method_added

  Method called when a singleton method is added to self.

• singleton_method_removed

  Method called when a singleton method is added removed from self.

• singleton_method_undefined

  Method called when a singleton method is undefined in self.