123456789_123456789_123456789_123456789_123456789_

Class: BasicObject

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, Qnil
Instance Chain:
self, Qnil
Inherits: Qnil
Defined in: class.c,
gc.c,
object.c,
vm_eval.c

Overview

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

Class Method Summary

  • .new constructor private

    Not documented.

Instance Method Summary

Constructor Details

.new (private)

Not documented

[ GitHub ]

  
# File 'object.c', line 1162

static VALUE
rb_obj_dummy(void)
{
    return Qnil;
}

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(symbol[, *args]) ⇒ result (private)

Invoked by Ruby when obj is sent a message it cannot handle. symbol is the symbol for the method called, and args are any arguments that were passed to it. By default, the interpreter raises an error when this method is called. However, it is possible to override the method to provide more dynamic behavior. If it is decided that a particular method should not be handled, then super should be called, so that ancestors can pick up the missing method. The example below creates a class Roman, which responds to methods with names consisting of roman numerals, returning the corresponding integer values.

class Roman
  def roman_to_int(str)
    # ...
  end

  def method_missing(symbol, *args)
    str = symbol.id2name
    begin
      roman_to_int(str)
    rescue
      super(symbol, *args)
    end
  end
end

r = Roman.new
r.iv      #=> 4
r.xxiii   #=> 23
r.mm      #=> 2000
r.foo     #=> NoMethodError
[ GitHub ]

  
# File 'vm_eval.c', line 655

static VALUE
rb_method_missing(int argc, const VALUE *argv, VALUE obj)
{
    rb_execution_context_t *ec = GET_EC();
    raise_method_missing(ec, argc, argv, obj, ec->method_missing_reason);
    UNREACHABLE_RETURN(Qnil);
}

Instance Method Details

#!Boolean

Boolean negate.

[ GitHub ]

  
# File 'object.c', line 243

MJIT_FUNC_EXPORTED VALUE
rb_obj_not(VALUE obj)
{
    return RTEST(obj) ? Qfalse : Qtrue;
}

#!=(other) ⇒ Boolean

Returns true if two objects are not-equal, otherwise false.

[ GitHub ]

  
# File 'object.c', line 259

MJIT_FUNC_EXPORTED VALUE
rb_obj_not_equal(VALUE obj1, VALUE obj2)
{
    VALUE result = rb_funcall(obj1, id_eq, 1, obj2);
    return RTEST(result) ? Qfalse : Qtrue;
}

#==(other) ⇒ Boolean #equal?(other) ⇒ Boolean #eql?(other) ⇒ Boolean
Also known as: #equal?

Equality — At the ::Object level, #== returns true only if obj and other are the same object. Typically, this method is overridden in descendant classes to provide class-specific meaning.

Unlike #==, the #equal? method should never be overridden by subclasses as it is used to determine object identity (that is, a.equal?(b) if and only if a is the same object as b):

obj = "a"
other = obj.dup

obj == other      #=> true
obj.equal? other  #=> false
obj.equal? obj    #=> true

The #eql? method returns true if obj and other refer to the same hash key. This is used by ::Hash to test members for equality. For any pair of objects where #eql? returns true, the #hash value of both objects must be equal. So any subclass that overrides #eql? should also override #hash appropriately.

For objects of class ::Object, #eql? is synonymous with #==. Subclasses normally continue this tradition by aliasing #eql? to their overridden #== method, but there are exceptions. ::Numeric types, for example, perform type conversion across #==, but not across #eql?, so:

1 == 1.0     #=> true
1.eql? 1.0   #=> false
[ GitHub ]

  
# File 'object.c', line 205

MJIT_FUNC_EXPORTED VALUE
rb_obj_equal(VALUE obj1, VALUE obj2)
{
    if (obj1 == obj2) return Qtrue;
    return Qfalse;
}

#__id__Integer #object_idInteger

Returns an integer identifier for obj.

The same number will be returned on all calls to object_id for a given object, and no two active objects will share an id.

Note: that some objects of builtin classes are reused for optimization. This is the case for immediate values and frozen string literals.

BasicObject implements __id__, ::Kernel implements object_id.

Immediate values are not passed by reference but are passed by value: nil, true, false, Fixnums, Symbols, and some Floats.

Object.new.object_id  == Object.new.object_id  # => false
(21 * 2).object_id    == (21 * 2).object_id    # => true
"hello".object_id     == "hello".object_id     # => false
"hi".freeze.object_id == "hi".freeze.object_id # => true
[ GitHub ]

  
# File 'gc.c', line 3547

VALUE
rb_obj_id(VALUE obj)
{
    /*
     *                32-bit VALUE space
     *          MSB ------------------------ LSB
     *  false   00000000000000000000000000000000
     *  true    00000000000000000000000000000010
     *  nil     00000000000000000000000000000100
     *  undef   00000000000000000000000000000110
     *  symbol  ssssssssssssssssssssssss00001110
     *  object  oooooooooooooooooooooooooooooo00        = 0 (mod sizeof(RVALUE))
     *  fixnum  fffffffffffffffffffffffffffffff1
     *
     *                    object_id space
     *                                       LSB
     *  false   00000000000000000000000000000000
     *  true    00000000000000000000000000000010
     *  nil     00000000000000000000000000000100
     *  undef   00000000000000000000000000000110
     *  symbol   000SSSSSSSSSSSSSSSSSSSSSSSSSSS0        S...S % A = 4 (S...S = s...s * A + 4)
     *  object   oooooooooooooooooooooooooooooo0        o...o % A = 0
     *  fixnum  fffffffffffffffffffffffffffffff1        bignum if required
     *
     *  where A = sizeof(RVALUE)/4
     *
     *  sizeof(RVALUE) is
     *  20 if 32-bit, double is 4-byte aligned
     *  24 if 32-bit, double is 8-byte aligned
     *  40 if 64-bit
     */

    return rb_find_object_id(obj, cached_object_id);
}

#send(symbol[, args...]) ⇒ Object #__send__(symbol[, args...]) ⇒ Object #send(string[, args...]) ⇒ Object #__send__(string[, args...]) ⇒ Object

Invokes the method identified by symbol, passing it any arguments specified. You can use __send__ if the name send clashes with an existing method in obj. When the method is identified by a string, the string is converted to a symbol.

BasicObject implements __send__, ::Kernel implements send.

class Klass
  def hello(*args)
    "Hello " + args.join(' ')
  end
end
k = Klass.new
k.send :hello, "gentle", "readers"   #=> "Hello gentle readers"
[ GitHub ]

  
# File 'vm_eval.c', line 971

VALUE
rb_f_send(int argc, VALUE *argv, VALUE recv)
{
    return send_internal(argc, argv, recv, CALL_FCALL);
}

#==(other) ⇒ Boolean #equal?(other) ⇒ Boolean #eql?(other) ⇒ Boolean

Alias for #==.

#instance_eval(string[, filename [, lineno]]) ⇒ Object #instance_eval {|obj| ... } ⇒ Object

Evaluates a string containing Ruby source code, or the given block, within the context of the receiver (obj). In order to set the context, the variable self is set to obj while the code is executing, giving the code access to obj's instance variables and private methods.

When instance_eval is given a block, obj is also passed in as the block's only argument.

When instance_eval is given a ::String, the optional second and third parameters supply a filename and starting line number that are used when reporting compilation errors.

class KlassWithSecret
  def initialize
    @secret = 99
  end
  private
  def the_secret
    "Ssssh! The secret is #{@secret}."
  end
end
k = KlassWithSecret.new
k.instance_eval { @secret }          #=> 99
k.instance_eval { the_secret }       #=> "Ssssh! The secret is 99."
k.instance_eval {|obj| obj == self } #=> true
[ GitHub ]

  
# File 'vm_eval.c', line 1711

VALUE
rb_obj_instance_eval(int argc, const VALUE *argv, VALUE self)
{
    VALUE klass = singleton_class_for_eval(self);
    return specific_eval(argc, argv, klass, self);
}

#instance_exec(arg...) {|var...| ... } ⇒ Object

Executes the given block within the context of the receiver (obj). In order to set the context, the variable self is set to obj while the code is executing, giving the code access to obj's instance variables. Arguments are passed as block parameters.

class KlassWithSecret
  def initialize
    @secret = 99
  end
end
k = KlassWithSecret.new
k.instance_exec(5) {|x| @secret+x }   #=> 104
[ GitHub ]

  
# File 'vm_eval.c', line 1736

VALUE
rb_obj_instance_exec(int argc, const VALUE *argv, VALUE self)
{
    VALUE klass = singleton_class_for_eval(self);
    return yield_under(klass, self, argc, argv);
}

#singleton_method_added(symbol) (private)

Invoked as a callback whenever a singleton method is added to the receiver.

module Chatty
  def Chatty.singleton_method_added(id)
    puts "Adding #{id.id2name}"
  end
  def self.one()     end
  def two()          end
  def Chatty.three() end
end

produces:

Adding singleton_method_added
Adding one
Adding three
[ GitHub ]

#singleton_method_removed(symbol) (private)

Invoked as a callback whenever a singleton method is removed from the receiver.

module Chatty
  def Chatty.singleton_method_removed(id)
    puts "Removing #{id.id2name}"
  end
  def self.one()     end
  def two()          end
  def Chatty.three() end
  class << self
    remove_method :three
    remove_method :one
  end
end

produces:

Removing three
Removing one
[ GitHub ]

#singleton_method_undefined(symbol) (private)

Invoked as a callback whenever a singleton method is undefined in the receiver.

module Chatty
  def Chatty.singleton_method_undefined(id)
    puts "Undefining #{id.id2name}"
  end
  def Chatty.one()   end
  class << self
     undef_method(:one)
  end
end

produces:

Undefining one
[ GitHub ]