class 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
).
What’s Here¶ ↑
First, what’s elsewhere. Class Object:
-
Inherits from class BasicObject.
-
Includes module Kernel.
Here, class Object provides methods for:
Querying¶ ↑
-
#!~: Returns
true
ifself
does not match the given object, otherwisefalse
. -
#<=>: Returns 0 if
self
and the given objectobject
are the same object, or ifself == object
; otherwise returnsnil
. -
===
: Implements case equality, effectively the same as calling==
. -
eql?
: Implements hash equality, effectively the same as calling==
. -
kind_of?
(aliased asis_a?
): Returns whether given argument is an ancestor of the singleton class ofself
. -
instance_of?
: Returns whetherself
is an instance of the given class. -
instance_variable_defined?
: Returns whether the given instance variable is defined inself
. -
method
: Returns theMethod
object for the given method inself
. -
methods
: Returns an array of symbol names of public and protected methods inself
. -
nil?
: Returnsfalse
. (Onlynil
respondstrue
to methodnil?
.) -
object_id
: Returns an integer corresponding toself
that is unique for the current process -
private_methods
: Returns an array of the symbol names of the private methods inself
. -
protected_methods
: Returns an array of the symbol names of the protected methods inself
. -
public_method
: Returns theMethod
object for the given public method inself
. -
public_methods
: Returns an array of the symbol names of the public methods inself
. -
respond_to?
: Returns whetherself
responds to the given method. -
singleton_class
: Returns the singleton class ofself
. -
singleton_method
: Returns theMethod
object for the given singleton method inself
. -
singleton_methods
: Returns an array of the symbol names of the singleton methods inself
. -
define_singleton_method
: Defines a singleton method inself
for the given symbol method-name and block or proc. -
extend
: Includes the given modules in the singleton class ofself
. -
public_send
: Calls the given public method inself
with the given argument. -
send
: Calls the given method inself
with the given argument.
Instance Variables¶ ↑
-
instance_variable_get
: Returns the value of the given instance variable inself
, ornil
if the instance variable is not set. -
instance_variable_set
: Sets the value of the given instance variable inself
to the given object. -
instance_variables
: Returns an array of the symbol names of the instance variables inself
. -
remove_instance_variable
: Removes the named instance variable fromself
.
Other¶ ↑
-
clone
: Returns a shallow copy ofself
, including singleton class and frozen state. -
define_singleton_method
: Defines a singleton method inself
for the given symbol method-name and block or proc. -
dup
: Returns a shallow unfrozen copy ofself
. -
enum_for
(aliased asto_enum
): Returns anEnumerator
forself
using the using the given method, arguments, and block. -
extend
: Includes the given modules in the singleton class ofself
. -
freeze
: Prevents further modifications toself
. -
hash
: Returns the integer hash value forself
. -
inspect
: Returns a human-readable string representation ofself
. -
itself
: Returnsself
. -
method_missing
:Method
called when an undefined method is called onself
. -
public_send
: Calls the given public method inself
with the given argument. -
send
: Calls the given method inself
with the given argument. -
to_s
: Returns a string representation ofself
.
Constants
- ARGF
ARGF
is a stream designed for use in scripts that process files given as command-line arguments or passed in viaSTDIN
.See
ARGF
(the class) for more details.- ARGV
ARGV
contains the command line arguments used to run ruby.A library like OptionParser can be used to process command-line arguments.
- DATA
DATA
is aFile
that contains the data section of the executed file. To create a data section use__END__
:$ cat t.rb puts DATA.gets __END__ hello world! $ ruby t.rb hello world!
- ENV
ENV is a Hash-like accessor for environment variables.
See
ENV
(the class) for more details.- RUBY_COPYRIGHT
The copyright string for ruby
- RUBY_DESCRIPTION
The full ruby version string, like
ruby -v
prints- RUBY_ENGINE
The engine or interpreter this ruby uses.
- RUBY_ENGINE_VERSION
The version of the engine or interpreter this ruby uses.
- RUBY_PATCHLEVEL
The patchlevel for this ruby. If this is a development build of ruby the patchlevel will be -1
- RUBY_PLATFORM
The platform for this ruby
- RUBY_RELEASE_DATE
The date this ruby was released
- RUBY_REVISION
The GIT commit hash for this ruby.
- RUBY_VERSION
The running version of ruby
- STDERR
Holds the original stderr
- STDIN
Holds the original stdin
- STDOUT
Holds the original stdout
- TOPLEVEL_BINDING
The
Binding
of the top level scope
Public Instance Methods
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 rb_obj_not(result); }
Returns 0 if obj
and other
are the same object or obj == other
, otherwise nil.
The #<=> is used by various methods to compare objects, for example Enumerable#sort
, Enumerable#max
etc.
Your implementation of #<=> should return one of the following values: -1, 0, 1 or nil. -1 means self is smaller than other. 0 means self is equal to other. 1 means self is bigger than other. Nil means the two values could not be compared.
When you define #<=>, you can include Comparable
to gain the methods #<=, #<, ==
, #>=, #> and between?.
static VALUE rb_obj_cmp(VALUE obj1, VALUE obj2) { if (rb_equal(obj1, obj2)) return INT2FIX(0); return Qnil; }
Defines a public 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. If a block or a method has parameters, they’re used as method parameters.
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!" chris = "Chris" chris.define_singleton_method(:greet) {|greeting| "#{greeting}, I'm Chris!" } chris.greet("Hi") #=> "Hi, I'm Chris!"
static VALUE rb_obj_define_method(int argc, VALUE *argv, VALUE obj) { VALUE klass = rb_singleton_class(obj); const rb_scope_visibility_t scope_visi = {METHOD_VISI_PUBLIC, FALSE}; return rb_mod_define_method_with_visibility(argc, argv, klass, &scope_visi); }
Writes self
on the given port:
1.display "cat".display [ 4, 5, 6 ].display puts
Output:
1cat[4, 5, 6]
static VALUE rb_obj_display(int argc, VALUE *argv, VALUE self) { VALUE out; out = (!rb_check_arity(argc, 0, 1) ? rb_ractor_stdout() : argv[0]); 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.
This method may have class-specific behavior. If so, that behavior will be documented under the #initialize_copy
method of the class.
on dup vs 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.
When using dup
, any modules that the object has been extended with will not be copied.
class Klass attr_accessor :str end module Foo def foo; 'foo'; end end s1 = Klass.new #=> #<Klass:0x401b3a38> s1.extend(Foo) #=> #<Klass:0x401b3a38> s1.foo #=> "foo" s2 = s1.clone #=> #<Klass:0x401be280> s2.foo #=> "foo" s3 = s1.dup #=> #<Klass:0x401c1084> s3.foo #=> NoMethodError: undefined method `foo' for #<Klass:0x401c1084>
VALUE rb_obj_dup(VALUE obj) { VALUE dup; if (special_object_p(obj)) { return obj; } dup = rb_obj_alloc(rb_obj_class(obj)); return rb_obj_dup_setup(obj, dup); }
Creates a new Enumerator
which will enumerate by calling method
on obj
, passing args
if any. What was yielded by method becomes values of enumerator.
If a block is given, it will be used to calculate the size of the enumerator without the need to iterate it (see Enumerator#size
).
Examples¶ ↑
str = "xyz" enum = str.enum_for(:each_byte) enum.each { |b| puts b } # => 120 # => 121 # => 122 # protect an array from being modified by some_method a = [1, 2, 3] some_method(a.to_enum) # String#split in block form is more memory-effective: very_large_string.split("|") { |chunk| return chunk if chunk.include?('DATE') } # This could be rewritten more idiomatically with to_enum: very_large_string.to_enum(:split, "|").lazy.grep(/DATE/).first
It is typical to call to_enum
when defining methods for a generic Enumerable
, in case no block is passed.
Here is such an example, with parameter passing and a sizing block:
module Enumerable # a generic method to repeat the values of any enumerable def repeat(n) raise ArgumentError, "#{n} is negative!" if n < 0 unless block_given? return to_enum(__method__, n) do # __method__ is :repeat here sz = size # Call size and multiply by n... sz * n if sz # but return nil if size itself is nil end end each do |*val| n.times { yield *val } end end end %i[hello world].repeat(2) { |w| puts w } # => Prints 'hello', 'hello', 'world', 'world' enum = (1..14).repeat(3) # => returns an Enumerator when called without a block enum.first(4) # => [1, 1, 1, 2] enum.size # => 42
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
VALUE rb_obj_equal(VALUE obj1, VALUE obj2) { return RBOOL(obj1 == obj2); }
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; ID id_extend_object, id_extended; CONST_ID(id_extend_object, "extend_object"); CONST_ID(id_extended, "extended"); rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS); for (i = 0; i < argc; i++) { Check_Type(argv[i], T_MODULE); if (FL_TEST(argv[i], RMODULE_IS_REFINEMENT)) { rb_raise(rb_eTypeError, "Cannot extend object with refinement"); } } while (argc--) { rb_funcall(argv[argc], id_extend_object, 1, obj); rb_funcall(argv[argc], id_extended, 1, obj); } return obj; }
Prevents further modifications to obj. A FrozenError
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 (FrozenError) from prog.rb:3
Objects of the following classes are always frozen: Integer
, Float
, Symbol
.
VALUE rb_obj_freeze(VALUE obj) { if (!OBJ_FROZEN(obj)) { OBJ_FREEZE(obj); if (SPECIAL_CONST_P(obj)) { rb_bug("special consts should be frozen."); } } return obj; }
Generates an Integer
hash value for this object. This function must have the property that a.eql?(b)
implies a.hash == b.hash
.
The hash value is used along with eql?
by the Hash
class to determine if two objects reference the same hash key. Any hash value that exceeds the capacity of an Integer
will be truncated before being used.
The hash value for an object may not be identical across invocations or implementations of Ruby. If you need a stable identifier across Ruby invocations and implementations you will need to generate one with a custom method.
Certain core classes such as Integer
use built-in hash calculations and do not call the hash
method when used as a hash key.
When implementing your own hash
based on multiple values, the best practice is to combine the class and any values using the hash code of an array:
For example:
def hash [self.class, a, b, c].hash end
The reason for this is that the Array#hash
method already has logic for safely and efficiently combining multiple hash values.
VALUE rb_obj_hash(VALUE obj) { long hnum = any_hash(obj, objid_hash); return ST2FIX(hnum); }
Returns a string containing a human-readable representation of obj. The default inspect
shows the object’s class name, an encoding of its memory address, and a list of the instance variables and their values (by calling inspect
on each of them). User defined classes should override this method to provide a better representation of obj. When overriding this method, it should return a string whose encoding is compatible with the default external encoding.
[ 1, 2, 3..4, 'five' ].inspect #=> "[1, 2, 3..4, \"five\"]" Time.new.inspect #=> "2008-03-08 19:43:39 +0900" class Foo end Foo.new.inspect #=> "#<Foo:0x0300c868>" class Bar def initialize @bar = 1 end end Bar.new.inspect #=> "#<Bar:0x0300c868 @bar=1>"
static VALUE rb_obj_inspect(VALUE obj) { if (rb_ivar_count(obj) > 0) { VALUE str; VALUE c = rb_class_name(CLASS_OF(obj)); str = rb_sprintf("-<%"PRIsVALUE":%p", c, (void*)obj); return rb_exec_recursive(inspect_obj, obj, str); } else { return rb_any_to_s(obj); } }
Returns true
if obj is an instance of the given class. See also Object#kind_of?
.
class A; 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
VALUE rb_obj_is_instance_of(VALUE obj, VALUE c) { c = class_or_module_required(c); return RBOOL(rb_obj_class(obj) == c); }
Returns true
if the given instance variable is defined in obj. String
arguments are converted to symbols.
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 = id_for_var(obj, iv, instance); if (!id) { return Qfalse; } 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. String
arguments are converted to symbols.
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 = id_for_var(obj, iv, instance); if (!id) { return Qnil; } return rb_ivar_get(obj, id); }
Sets the instance variable named by symbol to the given object. This may circumvent the encapsulation intended by the author of the class, so it should be used with care. The variable does not have to exist prior to this call. If the instance variable name is passed as a string, that string is converted to a symbol.
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_m(VALUE obj, VALUE iv, VALUE val) { ID id = id_for_var(obj, iv, instance); if (!id) id = rb_intern_str(iv); 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.is_a? A #=> true b.is_a? B #=> true b.is_a? C #=> false b.is_a? M #=> true b.kind_of? A #=> true b.kind_of? B #=> true b.kind_of? C #=> false b.kind_of? M #=> true
Returns the receiver.
string = "my string" string.itself.object_id == string.object_id #=> true
static VALUE rb_obj_itself(VALUE obj) { return obj; }
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.is_a? A #=> true b.is_a? B #=> true b.is_a? C #=> false b.is_a? M #=> true 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); RUBY_ASSERT(RB_TYPE_P(cl, T_CLASS)); // Fastest path: If the object's class is an exact match we know `c` is a // class without checking type and can return immediately. if (cl == c) return Qtrue; // Note: YJIT needs this function to never allocate and never raise when // `c` is a class or a module. if (LIKELY(RB_TYPE_P(c, T_CLASS))) { // Fast path: Both are T_CLASS return class_search_class_ancestor(cl, c); } else if (RB_TYPE_P(c, T_ICLASS)) { // First check if we inherit the includer // If we do we can return true immediately VALUE includer = RCLASS_INCLUDER(c); if (cl == includer) return Qtrue; // Usually includer is a T_CLASS here, except when including into an // already included Module. // If it is a class, attempt the fast class-to-class check and return // true if there is a match. if (RB_TYPE_P(includer, T_CLASS) && class_search_class_ancestor(cl, includer)) return Qtrue; // We don't include the ICLASS directly, so must check if we inherit // the module via another include return RBOOL(class_search_ancestor(cl, RCLASS_ORIGIN(c))); } else if (RB_TYPE_P(c, T_MODULE)) { // Slow path: check each ancestor in the linked list and its method table return RBOOL(class_search_ancestor(cl, RCLASS_ORIGIN(c))); } else { rb_raise(rb_eTypeError, "class or module required"); UNREACHABLE_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"
Note that Method
implements to_proc
method, which means it can be used with iterators.
[ 1, 2, 3 ].each(&method(:puts)) # => prints 3 lines to stdout out = File.open('test.txt', 'w') [ 1, 2, 3 ].each(&out.method(:puts)) # => prints 3 lines to file require 'date' %w[2017-03-01 2017-03-02].collect(&Date.method(:parse)) #=> [#<Date: 2017-03-01 ((2457814j,0s,0n),+0s,2299161j)>, #<Date: 2017-03-02 ((2457815j,0s,0n),+0s,2299161j)>]
VALUE rb_obj_method(VALUE obj, VALUE vid) { return obj_method(obj, vid, FALSE); }
Returns a list of the names of public and protected methods of obj. This will include all the methods accessible in obj’s ancestors. If the optional parameter is false
, it returns an array of obj’s public and protected singleton methods, the array will not include methods in modules included in obj.
class Klass def klass_method() end end k = Klass.new k.methods[0..9] #=> [:klass_method, :nil?, :===, # :==~, :!, :eql? # :hash, :<=>, :class, :singleton_class] k.methods.length #=> 56 k.methods(false) #=> [] def k.singleton_method; end k.methods(false) #=> [:singleton_method] module M123; def m123; end end k.extend M123 k.methods(false) #=> [:singleton_method]
VALUE rb_obj_methods(int argc, const VALUE *argv, VALUE obj) { rb_check_arity(argc, 0, 1); if (argc > 0 && !RTEST(argv[0])) { return rb_obj_singleton_methods(argc, argv, obj); } return class_instance_method_list(argc, argv, CLASS_OF(obj), 1, ins_methods_i); }
Only the object nil responds true
to nil?
.
Object.new.nil? #=> false nil.nil? #=> true
VALUE rb_false(VALUE obj) { return Qfalse; }
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
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); }
Returns the list of private methods accessible to obj. If the all parameter is set to false
, only those methods in the receiver will be listed.
VALUE rb_obj_private_methods(int argc, const VALUE *argv, VALUE obj) { return class_instance_method_list(argc, argv, CLASS_OF(obj), 1, ins_methods_priv_i); }
Returns the list of protected methods accessible to obj. If the all parameter is set to false
, only those methods in the receiver will be listed.
VALUE rb_obj_protected_methods(int argc, const VALUE *argv, VALUE obj) { return class_instance_method_list(argc, argv, CLASS_OF(obj), 1, ins_methods_prot_i); }
Similar to method, searches public method only.
VALUE rb_obj_public_method(VALUE obj, VALUE vid) { return obj_method(obj, vid, TRUE); }
Returns the list of public methods accessible to obj. If the all parameter is set to false
, only those methods in the receiver will be listed.
VALUE rb_obj_public_methods(int argc, const VALUE *argv, VALUE obj) { return class_instance_method_list(argc, argv, CLASS_OF(obj), 1, ins_methods_pub_i); }
Invokes the method identified by symbol, passing it any arguments specified. Unlike send, public_send
calls public methods only. When the method is identified by a string, the string is converted to a symbol.
1.public_send(:puts, "hello") # causes NoMethodError
static VALUE rb_f_public_send(int argc, VALUE *argv, VALUE recv) { return send_internal_kw(argc, argv, recv, CALL_PUBLIC); }
Removes the named instance variable from obj, returning that variable’s value. String
arguments are converted to symbols.
class Dummy attr_reader :var def initialize @var = 99 end def remove remove_instance_variable(:@var) end end d = Dummy.new d.var #=> 99 d.remove #=> 99 d.var #=> nil
VALUE rb_obj_remove_instance_variable(VALUE obj, VALUE name) { const ID id = id_for_var(obj, name, an, instance); // Frozen check comes here because it's expected that we raise a // NameError (from the id_for_var check) before we raise a FrozenError rb_check_frozen(obj); if (id) { VALUE val = rb_ivar_delete(obj, id, Qundef); if (val != Qundef) return val; } rb_name_err_raise("instance variable %1$s not defined", obj, name); UNREACHABLE_RETURN(Qnil); }
Returns true
if obj responds to the given method. Private and protected 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.
When the method name parameter is given as a string, the string is converted to a symbol.
static VALUE obj_respond_to(int argc, VALUE *argv, VALUE obj) { VALUE mid, priv; ID id; rb_execution_context_t *ec = GET_EC(); rb_scan_args(argc, argv, "11", &mid, &priv); if (!(id = rb_check_id(&mid))) { VALUE ret = basic_obj_respond_to_missing(ec, CLASS_OF(obj), obj, rb_to_symbol(mid), priv); if (UNDEF_P(ret)) ret = Qfalse; return ret; } return RBOOL(basic_obj_respond_to(ec, obj, id, !RTEST(priv))); }
DO NOT USE THIS DIRECTLY.
Hook method to return whether the obj can respond to id method or not.
When the method name parameter is given as a string, the string is converted to a symbol.
See respond_to?
, and the example of BasicObject
.
static VALUE obj_respond_to_missing(VALUE obj, VALUE mid, VALUE priv) { return Qfalse; }
Invokes the method identified by symbol, passing it any arguments specified. When the method is identified by a string, the string is converted to a symbol.
BasicObject
implements +__send__+, Kernel
implements send
. __send__
is safer than send
when obj has the same method name like Socket
. See also public_send
.
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_kw(argc, argv, recv, CALL_FCALL); }
Returns the singleton class of obj. This method creates a new singleton class if obj does not have one.
If obj is nil
, true
, or false
, it returns NilClass
, TrueClass
, or FalseClass
, respectively. If obj is an Integer
, a Float
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); }
Similar to method, searches singleton method only.
class Demo def initialize(n) @iv = n end def hello() "Hello, @iv = #{@iv}" end end k = Demo.new(99) def k.hi "Hi, @iv = #{@iv}" end m = k.singleton_method(:hi) m.call #=> "Hi, @iv = 99" m = k.singleton_method(:hello) #=> NameError
VALUE rb_obj_singleton_method(VALUE obj, VALUE vid) { VALUE klass = rb_singleton_class_get(obj); ID id = rb_check_id(&vid); if (NIL_P(klass) || NIL_P(klass = RCLASS_ORIGIN(klass)) || !NIL_P(rb_special_singleton_class(obj))) { /* goto undef; */ } else if (! id) { VALUE m = mnew_missing_by_name(klass, obj, &vid, FALSE, rb_cMethod); if (m) return m; /* else goto undef; */ } else { const rb_method_entry_t *me = rb_method_entry_at(klass, id); vid = ID2SYM(id); if (UNDEFINED_METHOD_ENTRY_P(me)) { /* goto undef; */ } else if (UNDEFINED_REFINED_METHOD_P(me->def)) { /* goto undef; */ } else { return mnew_from_me(me, klass, klass, obj, id, rb_cMethod, FALSE); } } /* undef: */ rb_name_err_raise("undefined singleton method `%1$s' for `%2$s'", obj, vid); UNREACHABLE_RETURN(Qundef); }
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, const VALUE *argv, VALUE obj) { VALUE ary, klass, origin; struct method_entry_arg me_arg; struct rb_id_table *mtbl; int recur = TRUE; if (rb_check_arity(argc, 0, 1)) recur = RTEST(argv[0]); if (RB_TYPE_P(obj, T_CLASS) && FL_TEST(obj, FL_SINGLETON)) { rb_singleton_class(obj); } klass = CLASS_OF(obj); origin = RCLASS_ORIGIN(klass); me_arg.list = st_init_numtable(); me_arg.recur = recur; if (klass && FL_TEST(klass, FL_SINGLETON)) { if ((mtbl = RCLASS_M_TBL(origin)) != 0) rb_id_table_foreach(mtbl, method_entry_i, &me_arg); klass = RCLASS_SUPER(klass); } if (recur) { while (klass && (FL_TEST(klass, FL_SINGLETON) || RB_TYPE_P(klass, T_ICLASS))) { if (klass != origin && (mtbl = RCLASS_M_TBL(klass)) != 0) rb_id_table_foreach(mtbl, method_entry_i, &me_arg); klass = RCLASS_SUPER(klass); } } ary = rb_ary_new2(me_arg.list->num_entries); st_foreach(me_arg.list, ins_methods_i, ary); st_free_table(me_arg.list); return ary; }
Creates a new Enumerator
which will enumerate by calling method
on obj
, passing args
if any. What was yielded by method becomes values of enumerator.
If a block is given, it will be used to calculate the size of the enumerator without the need to iterate it (see Enumerator#size
).
Examples¶ ↑
str = "xyz" enum = str.enum_for(:each_byte) enum.each { |b| puts b } # => 120 # => 121 # => 122 # protect an array from being modified by some_method a = [1, 2, 3] some_method(a.to_enum) # String#split in block form is more memory-effective: very_large_string.split("|") { |chunk| return chunk if chunk.include?('DATE') } # This could be rewritten more idiomatically with to_enum: very_large_string.to_enum(:split, "|").lazy.grep(/DATE/).first
It is typical to call to_enum
when defining methods for a generic Enumerable
, in case no block is passed.
Here is such an example, with parameter passing and a sizing block:
module Enumerable # a generic method to repeat the values of any enumerable def repeat(n) raise ArgumentError, "#{n} is negative!" if n < 0 unless block_given? return to_enum(__method__, n) do # __method__ is :repeat here sz = size # Call size and multiply by n... sz * n if sz # but return nil if size itself is nil end end each do |*val| n.times { yield *val } end end end %i[hello world].repeat(2) { |w| puts w } # => Prints 'hello', 'hello', 'world', 'world' enum = (1..14).repeat(3) # => returns an Enumerator when called without a block enum.first(4) # => [1, 1, 1, 2] enum.size # => 42
static VALUE obj_to_enum(int argc, VALUE *argv, VALUE obj) { VALUE enumerator, meth = sym_each; if (argc > 0) { --argc; meth = *argv++; } enumerator = rb_enumeratorize_with_size(obj, meth, argc, argv, 0); if (rb_block_given_p()) { RB_OBJ_WRITE(enumerator, &enumerator_ptr(enumerator)->size, rb_block_proc()); } return enumerator; }
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) { VALUE str; VALUE cname = rb_class_name(CLASS_OF(obj)); str = rb_sprintf("#<%"PRIsVALUE":%p>", cname, (void*)obj); return str; }