BasicObject and Object

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)
    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

BasicObject Reference

Object

Object is the default root of all Ruby objects. Object inherits from BasicObject which allows creating alternate object hierarchies. Methods on Object are available to all classes unless explicitly overridden.

Object mixes in the Kernel module, making the built-in kernel functions globally accessible. Although the instance methods of Object are defined by the Kernel module, we have chosen to document them here for clarity.

When referencing constants in classes inheriting from Object you do not need to use the full namespace. For example, referencing File inside YourClass will find the top-level File class.

In the descriptions of Object’s methods, the parameter symbol refers to a symbol, which is either a quoted string or a Symbol (such as :name).

Object Reference