Object is the root of Ruby's class hierarchy. Its methods 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.
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).
constants to hold original stdin/stdout/stderr
Returns true if two objects do not match (using the =~ method), otherwise false.
static VALUE
rb_obj_not_match(VALUE obj1, VALUE obj2)
{
VALUE result = rb_funcall(obj1, id_match, 1, obj2);
return RTEST(result) ? Qfalse : Qtrue;
}
Case Equality—For class Object, effectively the same as calling #==, but typically overridden by descendants to provide meaningful semantics in case statements.
VALUE
rb_equal(VALUE obj1, VALUE obj2)
{
VALUE result;
if (obj1 == obj2) return Qtrue;
result = rb_funcall(obj1, id_eq, 1, obj2);
if (RTEST(result)) return Qtrue;
return Qfalse;
}
Returns an integer identifier for obj. The same number will be returned on all calls to id for a given object, and no two active objects will share an id. Object#object_id is a different concept from the :name notation, which returns the symbol id of name. Replaces the deprecated 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 (TYPE(obj) == T_SYMBOL) {
return (SYM2ID(obj) * sizeof(RVALUE) + (4 << 2)) | FIXNUM_FLAG;
}
if (SPECIAL_CONST_P(obj)) {
return LONG2NUM((SIGNED_VALUE)obj);
}
return (VALUE)((SIGNED_VALUE)obj|FIXNUM_FLAG);
}
Returns the class of obj. This method must always be called with an explicit receiver, as class is also a reserved word in Ruby.
1.class #=> Fixnum self.class #=> Object
VALUE
rb_obj_class(VALUE obj)
{
return rb_class_real(CLASS_OF(obj));
}
Produces a shallow copy of obj—the instance variables of obj are copied, but not the objects they reference. Copies the frozen and tainted state of obj. See also the discussion under Object#dup.
class Klass attr_accessor :str end s1 = Klass.new #=> #<Klass:0x401b3a38> s1.str = "Hello" #=> "Hello" s2 = s1.clone #=> #<Klass:0x401b3998 @str="Hello"> s2.str[1,4] = "i" #=> "i" s1.inspect #=> "#<Klass:0x401b3a38 @str=\"Hi\">" s2.inspect #=> "#<Klass:0x401b3998 @str=\"Hi\">"
This method may have class-specific behavior. If so, that behavior will be documented under the #initialize_copy method of the class.
VALUE
rb_obj_clone(VALUE obj)
{
VALUE clone;
if (rb_special_const_p(obj)) {
rb_raise(rb_eTypeError, "can't clone %s", rb_obj_classname(obj));
}
clone = rb_obj_alloc(rb_obj_class(obj));
RBASIC(clone)->klass = rb_singleton_class_clone(obj);
RBASIC(clone)->flags = (RBASIC(obj)->flags | FL_TEST(clone, FL_TAINT) | FL_TEST(clone, FL_UNTRUSTED)) & ~(FL_FREEZE|FL_FINALIZE);
init_copy(clone, obj);
rb_funcall(clone, id_init_clone, 1, obj);
RBASIC(clone)->flags |= RBASIC(obj)->flags & FL_FREEZE;
return clone;
}
Defines a singleton method in the receiver. The method parameter can be a Proc, a Method or an UnboundMethod object. If a block is specified, it is used as the method body.
class A class << self def class_name to_s end end end A.define_singleton_method(:who_am_i) do "I am: #{class_name}" end A.who_am_i # ==> "I am: A" guy = "Bob" guy.define_singleton_method(:hello) { "#{self}: Hello there!" } guy.hello #=> "Bob: Hello there!"
static VALUE
rb_obj_define_method(int argc, VALUE *argv, VALUE obj)
{
VALUE klass = rb_singleton_class(obj);
return rb_mod_define_method(argc, argv, klass);
}
Prints obj on the given port (default $>). Equivalent to:
def display(port=$>) port.write self end
For example:
1.display "cat".display [ 4, 5, 6 ].display puts
produces:
1cat456
static VALUE
rb_obj_display(int argc, VALUE *argv, VALUE self)
{
VALUE out;
if (argc == 0) {
out = rb_stdout;
}
else {
rb_scan_args(argc, argv, "01", &out);
}
rb_io_write(out, self);
return Qnil;
}
Produces a shallow copy of obj—the instance variables of obj are copied, but not the objects they reference. dup copies the tainted state of obj. See also the discussion under Object#clone. In general, clone and dup may have different semantics in descendant classes. While clone is used to duplicate an object, including its internal state, dup typically uses the class of the descendant object to create the new instance.
This method may have class-specific behavior. If so, that behavior will be documented under the #initialize_copy method of the class.
VALUE
rb_obj_dup(VALUE obj)
{
VALUE dup;
if (rb_special_const_p(obj)) {
rb_raise(rb_eTypeError, "can't dup %s", rb_obj_classname(obj));
}
dup = rb_obj_alloc(rb_obj_class(obj));
init_copy(dup, obj);
rb_funcall(dup, id_init_dup, 1, obj);
return dup;
}
Returns Enumerator.new(self, method, *args).
e.g.:
str = "xyz" enum = str.enum_for(:each_byte) a = enum.map {|b| '%02x' % b } #=> ["78", "79", "7a"] # protects an array from being modified a = [1, 2, 3] some_method(a.to_enum)
static VALUE
obj_to_enum(int argc, VALUE *argv, VALUE obj)
{
VALUE meth = sym_each;
if (argc > 0) {
--argc;
meth = *argv++;
}
return rb_enumeratorize(obj, meth, argc, argv);
}
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: it is used to determine object identity (that is, a.equal?(b) iff a is the same object as b).
The eql? method returns true if obj and anObject have the same value. Used by Hash to test members for equality. For objects of class Object, eql? is synonymous with ==. Subclasses normally continue this tradition, 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
VALUE
rb_obj_equal(VALUE obj1, VALUE obj2)
{
if (obj1 == obj2) return Qtrue;
return Qfalse;
}
Adds to obj the instance methods from each module given as a parameter.
module Mod def hello "Hello from Mod.\n" end end class Klass def hello "Hello from Klass.\n" end end k = Klass.new k.hello #=> "Hello from Klass.\n" k.extend(Mod) #=> #<Klass:0x401b3bc8> k.hello #=> "Hello from Mod.\n"
static VALUE
rb_obj_extend(int argc, VALUE *argv, VALUE obj)
{
int i;
if (argc == 0) {
rb_raise(rb_eArgError, "wrong number of arguments (at least 1)");
}
for (i = 0; i < argc; i++)
Check_Type(argv[i], T_MODULE);
while (argc--) {
rb_funcall(argv[argc], rb_intern("extend_object"), 1, obj);
rb_funcall(argv[argc], rb_intern("extended"), 1, obj);
}
return obj;
}
Prevents further modifications to obj. A RuntimeError will be raised if modification is attempted. There is no way to unfreeze a frozen object. See also Object#frozen?.
This method returns self.
a = [ "a", "b", "c" ] a.freeze a << "z"
produces:
prog.rb:3:in `<<': can't modify frozen array (RuntimeError) from prog.rb:3
VALUE
rb_obj_freeze(VALUE obj)
{
if (!OBJ_FROZEN(obj)) {
if (rb_safe_level() >= 4 && !OBJ_UNTRUSTED(obj)) {
rb_raise(rb_eSecurityError, "Insecure: can't freeze object");
}
OBJ_FREEZE(obj);
if (SPECIAL_CONST_P(obj)) {
if (!immediate_frozen_tbl) {
immediate_frozen_tbl = st_init_numtable();
}
st_insert(immediate_frozen_tbl, obj, (st_data_t)Qtrue);
}
}
return obj;
}
Returns the freeze status of obj.
a = [ "a", "b", "c" ] a.freeze #=> ["a", "b", "c"] a.frozen? #=> true
VALUE
rb_obj_frozen_p(VALUE obj)
{
if (OBJ_FROZEN(obj)) return Qtrue;
if (SPECIAL_CONST_P(obj)) {
if (!immediate_frozen_tbl) return Qfalse;
if (st_lookup(immediate_frozen_tbl, obj, 0)) return Qtrue;
}
return Qfalse;
}
VALUE
rb_obj_hash(VALUE obj)
{
VALUE oid = rb_obj_id(obj);
st_index_t h = rb_hash_end(rb_hash_start(NUM2LONG(oid)));
return LONG2FIX(h);
}
Returns a string containing a human-readable representation of obj. If not overridden and no instance variables, uses the to_s method to generate the string. obj. If not overridden, uses the to_s method to generate the string.
[ 1, 2, 3..4, 'five' ].inspect #=> "[1, 2, 3..4, \"five\"]" Time.new.inspect #=> "2008-03-08 19:43:39 +0900"
static VALUE
rb_obj_inspect(VALUE obj)
{
extern int rb_obj_basic_to_s_p(VALUE);
if (TYPE(obj) == T_OBJECT && rb_obj_basic_to_s_p(obj)) {
int has_ivar = 0;
VALUE *ptr = ROBJECT_IVPTR(obj);
long len = ROBJECT_NUMIV(obj);
long i;
for (i = 0; i < len; i++) {
if (ptr[i] != Qundef) {
has_ivar = 1;
break;
}
}
if (has_ivar) {
VALUE str;
const char *c = rb_obj_classname(obj);
str = rb_sprintf("-<%s:%p", c, (void*)obj);
return rb_exec_recursive(inspect_obj, obj, str);
}
return rb_any_to_s(obj);
}
return rb_funcall(obj, rb_intern("to_s"), 0, 0);
}
Returns true if obj is an instance of the given class. See also Object#kind_of?.
VALUE
rb_obj_is_instance_of(VALUE obj, VALUE c)
{
switch (TYPE(c)) {
case T_MODULE:
case T_CLASS:
case T_ICLASS:
break;
default:
rb_raise(rb_eTypeError, "class or module required");
}
if (rb_obj_class(obj) == c) return Qtrue;
return Qfalse;
}
Returns true if the given instance variable is defined in obj.
class Fred def initialize(p1, p2) @a, @b = p1, p2 end end fred = Fred.new('cat', 99) fred.instance_variable_defined?(:@a) #=> true fred.instance_variable_defined?("@b") #=> true fred.instance_variable_defined?("@c") #=> false
static VALUE
rb_obj_ivar_defined(VALUE obj, VALUE iv)
{
ID id = rb_to_id(iv);
if (!rb_is_instance_id(id)) {
rb_name_error(id, "`%s' is not allowed as an instance variable name", rb_id2name(id));
}
return rb_ivar_defined(obj, id);
}
Returns the value of the given instance variable, or nil if the instance variable is not set. The @ part of the variable name should be included for regular instance variables. Throws a NameError exception if the supplied symbol is not valid as an instance variable name.
class Fred def initialize(p1, p2) @a, @b = p1, p2 end end fred = Fred.new('cat', 99) fred.instance_variable_get(:@a) #=> "cat" fred.instance_variable_get("@b") #=> 99
static VALUE
rb_obj_ivar_get(VALUE obj, VALUE iv)
{
ID id = rb_to_id(iv);
if (!rb_is_instance_id(id)) {
rb_name_error(id, "`%s' is not allowed as an instance variable name", rb_id2name(id));
}
return rb_ivar_get(obj, id);
}
Sets the instance variable names by symbol to object, thereby frustrating the efforts of the class’s author to attempt to provide proper encapsulation. The variable did not have to exist prior to this call.
class Fred def initialize(p1, p2) @a, @b = p1, p2 end end fred = Fred.new('cat', 99) fred.instance_variable_set(:@a, 'dog') #=> "dog" fred.instance_variable_set(:@c, 'cat') #=> "cat" fred.inspect #=> "#<Fred:0x401b3da8 @a=\"dog\", @b=99, @c=\"cat\">"
static VALUE
rb_obj_ivar_set(VALUE obj, VALUE iv, VALUE val)
{
ID id = rb_to_id(iv);
if (!rb_is_instance_id(id)) {
rb_name_error(id, "`%s' is not allowed as an instance variable name", rb_id2name(id));
}
return rb_ivar_set(obj, id, val);
}
Returns an array of instance variable names for the receiver. Note that simply defining an accessor does not create the corresponding instance variable.
class Fred attr_accessor :a1 def initialize @iv = 3 end end Fred.new.instance_variables #=> [:@iv]
VALUE
rb_obj_instance_variables(VALUE obj)
{
VALUE ary;
ary = rb_ary_new();
rb_ivar_foreach(obj, ivar_i, ary);
return ary;
}
Returns true if class is the class of obj, or if class is one of the superclasses of obj or modules included in obj.
module M; end class A include M end class B < A; end class C < B; end b = B.new b.instance_of? A #=> false b.instance_of? B #=> true b.instance_of? C #=> false b.instance_of? M #=> false b.kind_of? A #=> true b.kind_of? B #=> true b.kind_of? C #=> false b.kind_of? M #=> true
VALUE
rb_obj_is_kind_of(VALUE obj, VALUE c)
{
VALUE cl = CLASS_OF(obj);
switch (TYPE(c)) {
case T_MODULE:
case T_CLASS:
case T_ICLASS:
break;
default:
rb_raise(rb_eTypeError, "class or module required");
}
while (cl) {
if (cl == c || RCLASS_M_TBL(cl) == RCLASS_M_TBL(c))
return Qtrue;
cl = RCLASS_SUPER(cl);
}
return Qfalse;
}
Returns true if class is the class of obj, or if class is one of the superclasses of obj or modules included in obj.
module M; end class A include M end class B < A; end class C < B; end b = B.new b.instance_of? A #=> false b.instance_of? B #=> true b.instance_of? C #=> false b.instance_of? M #=> false b.kind_of? A #=> true b.kind_of? B #=> true b.kind_of? C #=> false b.kind_of? M #=> true
VALUE
rb_obj_is_kind_of(VALUE obj, VALUE c)
{
VALUE cl = CLASS_OF(obj);
switch (TYPE(c)) {
case T_MODULE:
case T_CLASS:
case T_ICLASS:
break;
default:
rb_raise(rb_eTypeError, "class or module required");
}
while (cl) {
if (cl == c || RCLASS_M_TBL(cl) == RCLASS_M_TBL(c))
return Qtrue;
cl = RCLASS_SUPER(cl);
}
return Qfalse;
}
Looks up the named method as a receiver in obj, returning a Method object (or raising NameError). The Method object acts as a closure in obj’s object instance, so instance variables and the value of self remain available.
class Demo def initialize(n) @iv = n end def hello() "Hello, @iv = #{@iv}" end end k = Demo.new(99) m = k.method(:hello) m.call #=> "Hello, @iv = 99" l = Demo.new('Fred') m = l.method("hello") m.call #=> "Hello, @iv = Fred"
VALUE
rb_obj_method(VALUE obj, VALUE vid)
{
return mnew(CLASS_OF(obj), obj, rb_to_id(vid), rb_cMethod, FALSE);
}
call_seq:
nil.nil? -> true <anything_else>.nil? -> false
Only the object nil responds true to nil?.
static VALUE
rb_false(VALUE obj)
{
return Qfalse;
}
Returns an integer identifier for obj. The same number will be returned on all calls to id for a given object, and no two active objects will share an id. Object#object_id is a different concept from the :name notation, which returns the symbol id of name. Replaces the deprecated 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 (TYPE(obj) == T_SYMBOL) {
return (SYM2ID(obj) * sizeof(RVALUE) + (4 << 2)) | FIXNUM_FLAG;
}
if (SPECIAL_CONST_P(obj)) {
return LONG2NUM((SIGNED_VALUE)obj);
}
return (VALUE)((SIGNED_VALUE)obj|FIXNUM_FLAG);
}
Similar to method, searches public method only.
VALUE
rb_obj_public_method(VALUE obj, VALUE vid)
{
return mnew(CLASS_OF(obj), obj, rb_to_id(vid), rb_cMethod, TRUE);
}
Invokes the method identified by symbol, passing it any arguments specified. Unlike send, public_send calls public methods only.
1.public_send(:puts, "hello") # causes NoMethodError
VALUE
rb_f_public_send(int argc, VALUE *argv, VALUE recv)
{
return send_internal(argc, argv, recv, CALL_PUBLIC);
}
Returns true if obj responds to the given method. Private methods are included in the search only if the optional second parameter evaluates to true.
If the method is not implemented, as Process.fork on Windows, File.lchmod on GNU/Linux, etc., false is returned.
If the method is not defined, respond_to_missing? method is called and the result is returned.
static VALUE
obj_respond_to(int argc, VALUE *argv, VALUE obj)
{
VALUE mid, priv;
ID id;
rb_scan_args(argc, argv, "11", &mid, &priv);
id = rb_to_id(mid);
if (basic_obj_respond_to(obj, id, !RTEST(priv)))
return Qtrue;
return Qfalse;
}
Hook method to return whether the obj can respond to id method or not.
See respond_to?.
static VALUE
obj_respond_to_missing(VALUE obj, VALUE priv)
{
return Qfalse;
}
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.
class Klass def hello(*args) "Hello " + args.join(' ') end end k = Klass.new k.send :hello, "gentle", "readers" #=> "Hello gentle readers"
VALUE
rb_f_send(int argc, VALUE *argv, VALUE recv)
{
return send_internal(argc, argv, recv, CALL_FCALL);
}
Returns the singleton class of obj. This method creates a new singleton class if obj does not have it.
If obj is nil, true, or false, it returns NilClass, TrueClass, or FalseClass, respectively. If obj is a Fixnum or a Symbol, it raises a TypeError.
Object.new.singleton_class #=> #<Class:#<Object:0xb7ce1e24>> String.singleton_class #=> #<Class:String> nil.singleton_class #=> NilClass
static VALUE
rb_obj_singleton_class(VALUE obj)
{
return rb_singleton_class(obj);
}
Returns an array of the names of singleton methods for obj. If the optional all parameter is true, the list will include methods in modules included in obj. Only public and protected singleton methods are returned.
module Other def three() end end class Single def Single.four() end end a = Single.new def a.one() end class << a include Other def two() end end Single.singleton_methods #=> [:four] a.singleton_methods(false) #=> [:two, :one] a.singleton_methods #=> [:two, :one, :three]
VALUE
rb_obj_singleton_methods(int argc, VALUE *argv, VALUE obj)
{
VALUE recur, ary, klass;
st_table *list;
if (argc == 0) {
recur = Qtrue;
}
else {
rb_scan_args(argc, argv, "01", &recur);
}
klass = CLASS_OF(obj);
list = st_init_numtable();
if (klass && FL_TEST(klass, FL_SINGLETON)) {
st_foreach(RCLASS_M_TBL(klass), method_entry, (st_data_t)list);
klass = RCLASS_SUPER(klass);
}
if (RTEST(recur)) {
while (klass && (FL_TEST(klass, FL_SINGLETON) || TYPE(klass) == T_ICLASS)) {
st_foreach(RCLASS_M_TBL(klass), method_entry, (st_data_t)list);
klass = RCLASS_SUPER(klass);
}
}
ary = rb_ary_new();
st_foreach(list, ins_methods_i, ary);
st_free_table(list);
return ary;
}
Marks obj as tainted—if the $SAFE level is set appropriately, many method calls which might alter the running programs environment will refuse to accept tainted strings.
VALUE
rb_obj_taint(VALUE obj)
{
rb_secure(4);
if (!OBJ_TAINTED(obj)) {
if (OBJ_FROZEN(obj)) {
rb_error_frozen("object");
}
OBJ_TAINT(obj);
}
return obj;
}
Returns true if the object is tainted.
VALUE
rb_obj_tainted(VALUE obj)
{
if (OBJ_TAINTED(obj))
return Qtrue;
return Qfalse;
}
Yields x to the block, and then returns x. The primary purpose of this method is to “tap into” a method chain, in order to perform operations on intermediate results within the chain.
(1..10) .tap {|x| puts "original: #{x.inspect}"} .to_a .tap {|x| puts "array: #{x.inspect}"} .select {|x| x%2==0} .tap {|x| puts "evens: #{x.inspect}"} .map { |x| x*x } .tap {|x| puts "squares: #{x.inspect}"}
VALUE
rb_obj_tap(VALUE obj)
{
rb_yield(obj);
return obj;
}
Returns Enumerator.new(self, method, *args).
e.g.:
str = "xyz" enum = str.enum_for(:each_byte) a = enum.map {|b| '%02x' % b } #=> ["78", "79", "7a"] # protects an array from being modified a = [1, 2, 3] some_method(a.to_enum)
static VALUE
obj_to_enum(int argc, VALUE *argv, VALUE obj)
{
VALUE meth = sym_each;
if (argc > 0) {
--argc;
meth = *argv++;
}
return rb_enumeratorize(obj, meth, argc, argv);
}
Returns a string representing obj. The default to_s prints the object’s class and an encoding of the object id. As a special case, the top-level object that is the initial execution context of Ruby programs returns “main.”
VALUE
rb_any_to_s(VALUE obj)
{
const char *cname = rb_obj_classname(obj);
VALUE str;
str = rb_sprintf("#<%s:%p>", cname, (void*)obj);
OBJ_INFECT(str, obj);
return str;
}
Removes the untrusted mark from obj.
VALUE
rb_obj_trust(VALUE obj)
{
rb_secure(3);
if (OBJ_UNTRUSTED(obj)) {
if (OBJ_FROZEN(obj)) {
rb_error_frozen("object");
}
FL_UNSET(obj, FL_UNTRUSTED);
}
return obj;
}
Removes the taint from obj.
VALUE
rb_obj_untaint(VALUE obj)
{
rb_secure(3);
if (OBJ_TAINTED(obj)) {
if (OBJ_FROZEN(obj)) {
rb_error_frozen("object");
}
FL_UNSET(obj, FL_TAINT);
}
return obj;
}