class BasicObject - Documentation for Ruby 2.3.0 (original) (raw)

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

Public Class Methods

new() click to toggle source

Not documented

static VALUE rb_obj_dummy(void) { return Qnil; }

Public Instance Methods

!obj → true or false click to toggle source

Boolean negate.

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

obj != other → true or false click to toggle source

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

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

obj == other → true or false click to toggle source

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
obj.equal? other
obj.equal? obj

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 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
1.eql? 1.0

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

__id__ → integer click to toggle source

object_id → integer

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.

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
(21 * 2).object_id == (21 * 2).object_id
"hello".object_id == "hello".object_id
"hi".freeze.object_id == "hi".freeze.object_id

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 */ if (STATIC_SYM_P(obj)) { return (SYM2ID(obj) * sizeof(RVALUE) + (4 << 2)) | FIXNUM_FLAG; } else if (FLONUM_P(obj)) { #if SIZEOF_LONG == SIZEOF_VOIDP return LONG2NUM((SIGNED_VALUE)obj); #else return LL2NUM((SIGNED_VALUE)obj); #endif } else if (SPECIAL_CONST_P(obj)) { return LONG2NUM((SIGNED_VALUE)obj); } return nonspecial_obj_id(obj); }

send(symbol [, args...]) → obj click to toggle source

__send__(symbol [, args...]) → obj

send(string [, args...]) → obj

__send__(string [, args...]) → obj

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.

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

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

equal?(other) → true or false click to toggle source

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
obj.equal? other
obj.equal? obj

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 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
1.eql? 1.0

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

instance_eval(string [, filename [, lineno]] ) → obj click to toggle source

instance_eval {|obj| block } → obj

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 }
k.instance_eval { the_secret }
k.instance_eval {|obj| obj == self }

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...| block } → obj click to toggle source

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 }

VALUE rb_obj_instance_exec(int argc, const VALUE *argv, VALUE self) { VALUE klass = singleton_class_for_eval(self); return yield_under(klass, self, rb_ary_new4(argc, argv)); }

Private Instance Methods

method_missing(symbol [, *args] ) → result click to toggle source

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(methId) str = methId.id2name roman_to_int(str) end end

r = Roman.new r.iv
r.xxiii
r.mm

static VALUE rb_method_missing(int argc, const VALUE *argv, VALUE obj) { rb_thread_t *th = GET_THREAD(); raise_method_missing(th, argc, argv, obj, th->method_missing_reason); UNREACHABLE; }

singleton_method_added(symbol) click to toggle source

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

static VALUE rb_obj_dummy(void) { return Qnil; }

singleton_method_removed(symbol) click to toggle source

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

static VALUE rb_obj_dummy(void) { return Qnil; }

singleton_method_undefined(symbol) click to toggle source

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

static VALUE rb_obj_dummy(void) { return Qnil; }