A Module is a collection of methods and constants. The methods in a module may be instance methods or module methods. Instance methods appear as methods in a class when the module is included, module methods do not. Conversely, module methods may be called without creating an encapsulating object, while instance methods may not. (See Module#module_function)
In the descriptions that follow, the parameter sym refers to a symbol, which is either a quoted string or a Symbol (such as :name).
module Mod include Math CONST = 1 def meth # ... end end Mod.class #=> Module Mod.constants #=> [:CONST, :PI, :E] Mod.instance_methods #=> [:meth]
Returns an array of the names of all constants defined in the system. This list includes the names of all modules and classes.
p Module.constants.sort[1..5]
produces:
["ARGV", "ArgumentError", "Array", "Bignum", "Binding"]
static VALUE
rb_mod_s_constants(int argc, VALUE *argv, VALUE mod)
{
const NODE *cref = rb_vm_cref();
VALUE klass;
VALUE cbase = 0;
void *data = 0;
if (argc > 0) {
return rb_mod_constants(argc, argv, rb_cModule);
}
while (cref) {
klass = cref->nd_clss;
if (!NIL_P(klass)) {
data = rb_mod_const_at(cref->nd_clss, data);
if (!cbase) {
cbase = klass;
}
}
cref = cref->nd_next;
}
if (cbase) {
data = rb_mod_const_of(cbase, data);
}
return rb_const_list(data);
}
Returns the list of Modules nested at the point of call.
module M1 module M2 $a = Module.nesting end end $a #=> [M1::M2, M1] $a[0].name #=> "M1::M2"
static VALUE
rb_mod_nesting(void)
{
VALUE ary = rb_ary_new();
const NODE *cref = rb_vm_cref();
while (cref && cref->nd_next) {
VALUE klass = cref->nd_clss;
if (!(cref->flags & NODE_FL_CREF_PUSHED_BY_EVAL) &&
!NIL_P(klass)) {
rb_ary_push(ary, klass);
}
cref = cref->nd_next;
}
return ary;
}
Creates a new anonymous module. If a block is given, it is passed the module object, and the block is evaluated in the context of this module using module_eval.
Fred = Module.new do def meth1 "hello" end def meth2 "bye" end end a = "my string" a.extend(Fred) #=> "my string" a.meth1 #=> "hello" a.meth2 #=> "bye"
static VALUE
rb_mod_initialize(VALUE module)
{
extern VALUE rb_mod_module_exec(int argc, VALUE *argv, VALUE mod);
if (rb_block_given_p()) {
rb_mod_module_exec(1, &module, module);
}
return Qnil;
}
Returns true if mod is a subclass of other. Returns nil if there’s no relationship between the two. (Think of the relationship in terms of the class definition: “class A<B” implies “A<B”).
static VALUE
rb_mod_lt(VALUE mod, VALUE arg)
{
if (mod == arg) return Qfalse;
return rb_class_inherited_p(mod, arg);
}
Returns true if mod is a subclass of other or is the same as other. Returns nil if there’s no relationship between the two. (Think of the relationship in terms of the class definition: “class A<B” implies “A<B”).
VALUE
rb_class_inherited_p(VALUE mod, VALUE arg)
{
VALUE start = mod;
if (mod == arg) return Qtrue;
switch (TYPE(arg)) {
case T_MODULE:
case T_CLASS:
break;
default:
rb_raise(rb_eTypeError, "compared with non class/module");
}
while (mod) {
if (RCLASS_M_TBL(mod) == RCLASS_M_TBL(arg))
return Qtrue;
mod = RCLASS_SUPER(mod);
}
/* not mod < arg; check if mod > arg */
while (arg) {
if (RCLASS_M_TBL(arg) == RCLASS_M_TBL(start))
return Qfalse;
arg = RCLASS_SUPER(arg);
}
return Qnil;
}
Comparison—Returns -1 if mod includes other_mod, 0 if mod is the same as other_mod, and +1 if mod is included by other_mod. Returns nil if mod has no relationship with other_mod or if other_mod is not a module.
static VALUE
rb_mod_cmp(VALUE mod, VALUE arg)
{
VALUE cmp;
if (mod == arg) return INT2FIX(0);
switch (TYPE(arg)) {
case T_MODULE:
case T_CLASS:
break;
default:
return Qnil;
}
cmp = rb_class_inherited_p(mod, arg);
if (NIL_P(cmp)) return Qnil;
if (cmp) {
return INT2FIX(-1);
}
return INT2FIX(1);
}
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;
}
Case Equality—Returns true if anObject is an instance of mod or one of mod’s descendants. Of limited use for modules, but can be used in case statements to classify objects by class.
static VALUE
rb_mod_eqq(VALUE mod, VALUE arg)
{
return rb_obj_is_kind_of(arg, mod);
}
Returns true if mod is an ancestor of other. Returns nil if there’s no relationship between the two. (Think of the relationship in terms of the class definition: “class A<B” implies “B>A”).
static VALUE
rb_mod_gt(VALUE mod, VALUE arg)
{
if (mod == arg) return Qfalse;
return rb_mod_ge(mod, arg);
}
Returns true if mod is an ancestor of other, or the two modules are the same. Returns nil if there’s no relationship between the two. (Think of the relationship in terms of the class definition: “class A<B” implies “B>A”).
static VALUE
rb_mod_ge(VALUE mod, VALUE arg)
{
switch (TYPE(arg)) {
case T_MODULE:
case T_CLASS:
break;
default:
rb_raise(rb_eTypeError, "compared with non class/module");
}
return rb_class_inherited_p(arg, mod);
}
Returns a list of modules included in mod (including mod itself).
module Mod include Math include Comparable end Mod.ancestors #=> [Mod, Comparable, Math] Math.ancestors #=> [Math]
VALUE
rb_mod_ancestors(VALUE mod)
{
VALUE p, ary = rb_ary_new();
for (p = mod; p; p = RCLASS_SUPER(p)) {
if (FL_TEST(p, FL_SINGLETON))
continue;
if (BUILTIN_TYPE(p) == T_ICLASS) {
rb_ary_push(ary, RBASIC(p)->klass);
}
else {
rb_ary_push(ary, p);
}
}
return ary;
}
Registers filename to be loaded (using Kernel::require) the first time that module (which may be a String or a symbol) is accessed in the namespace of mod.
module A end A.autoload(:B, "b") A::B.doit # autoloads "b"
static VALUE
rb_mod_autoload(VALUE mod, VALUE sym, VALUE file)
{
ID id = rb_to_id(sym);
FilePathValue(file);
rb_autoload(mod, id, RSTRING_PTR(file));
return Qnil;
}
Returns filename to be loaded if name is registered as autoload in the namespace of mod.
module A end A.autoload(:B, "b") A.autoload?(:B) #=> "b"
static VALUE
rb_mod_autoload_p(VALUE mod, VALUE sym)
{
return rb_autoload_p(mod, rb_to_id(sym));
}
Evaluates the string or block in the context of mod. This can be used to add methods to a class. module_eval returns the result of evaluating its argument. The optional filename and lineno parameters set the text for error messages.
class Thing end a = %q{def hello() "Hello there!" end} Thing.module_eval(a) puts Thing.new.hello() Thing.module_eval("invalid code", "dummy", 123)
produces:
Hello there! dummy:123:in `module_eval': undefined local variable or method `code' for Thing:Class
VALUE
rb_mod_module_eval(int argc, VALUE *argv, VALUE mod)
{
return specific_eval(argc, argv, mod, mod);
}
Evaluates the given block in the context of the class/module. The method defined in the block will belong to the receiver.
class Thing end Thing.class_exec{ def hello() "Hello there!" end } puts Thing.new.hello()
produces:
Hello there!
VALUE
rb_mod_module_exec(int argc, VALUE *argv, VALUE mod)
{
return yield_under(mod, mod, rb_ary_new4(argc, argv));
}
Returns true if the given class variable is defined in obj.
class Fred @@foo = 99 end Fred.class_variable_defined?(:@@foo) #=> true Fred.class_variable_defined?(:@@bar) #=> false
static VALUE
rb_mod_cvar_defined(VALUE obj, VALUE iv)
{
ID id = rb_to_id(iv);
if (!rb_is_class_id(id)) {
rb_name_error(id, "`%s' is not allowed as a class variable name", rb_id2name(id));
}
return rb_cvar_defined(obj, id);
}
Returns the value of the given class variable (or throws a NameError exception). The @@ part of the variable name should be included for regular class variables
class Fred @@foo = 99 end Fred.class_variable_get(:@@foo) #=> 99
static VALUE
rb_mod_cvar_get(VALUE obj, VALUE iv)
{
ID id = rb_to_id(iv);
if (!rb_is_class_id(id)) {
rb_name_error(id, "`%s' is not allowed as a class variable name", rb_id2name(id));
}
return rb_cvar_get(obj, id);
}
Sets the class variable names by symbol to object.
class Fred @@foo = 99 def foo @@foo end end Fred.class_variable_set(:@@foo, 101) #=> 101 Fred.new.foo #=> 101
static VALUE
rb_mod_cvar_set(VALUE obj, VALUE iv, VALUE val)
{
ID id = rb_to_id(iv);
if (!rb_is_class_id(id)) {
rb_name_error(id, "`%s' is not allowed as a class variable name", rb_id2name(id));
}
rb_cvar_set(obj, id, val);
return val;
}
Returns an array of the names of class variables in mod.
class One @@var1 = 1 end class Two < One @@var2 = 2 end One.class_variables #=> [:@@var1] Two.class_variables #=> [:@@var2]
VALUE
rb_mod_class_variables(VALUE obj)
{
VALUE ary = rb_ary_new();
if (RCLASS_IV_TBL(obj)) {
st_foreach_safe(RCLASS_IV_TBL(obj), cv_i, ary);
}
return ary;
}
Returns true if a constant with the given name is defined by mod, or its ancestors if inherit is not false.
Math.const_defined? "PI" #=> true IO.const_defined? "SYNC" #=> true IO.const_defined? "SYNC", false #=> false
static VALUE
rb_mod_const_defined(int argc, VALUE *argv, VALUE mod)
{
VALUE name, recur;
ID id;
if (argc == 1) {
name = argv[0];
recur = Qtrue;
}
else {
rb_scan_args(argc, argv, "11", &name, &recur);
}
id = rb_to_id(name);
if (!rb_is_const_id(id)) {
rb_name_error(id, "wrong constant name %s", rb_id2name(id));
}
return RTEST(recur) ? rb_const_defined(mod, id) : rb_const_defined_at(mod, id);
}
Returns the value of the named constant in mod.
Math.const_get(:PI) #=> 3.14159265358979
If the constant is not defined or is defined by the ancestors and inherit is false, NameError will be raised.
static VALUE
rb_mod_const_get(int argc, VALUE *argv, VALUE mod)
{
VALUE name, recur;
ID id;
if (argc == 1) {
name = argv[0];
recur = Qtrue;
}
else {
rb_scan_args(argc, argv, "11", &name, &recur);
}
id = rb_to_id(name);
if (!rb_is_const_id(id)) {
rb_name_error(id, "wrong constant name %s", rb_id2name(id));
}
return RTEST(recur) ? rb_const_get(mod, id) : rb_const_get_at(mod, id);
}
Invoked when a reference is made to an undefined constant in mod. It is passed a symbol for the undefined constant, and returns a value to be used for that constant. The following code is a (very bad) example: if reference is made to an undefined constant, it attempts to load a file whose name is the lowercase version of the constant (thus class Fred is assumed to be in file fred.rb). If found, it returns the value of the loaded class. It therefore implements a perverse kind of autoload facility.
def Object.const_missing(name) @looked_for ||= {} str_name = name.to_s raise "Class not found: #{name}" if @looked_for[str_name] @looked_for[str_name] = 1 file = str_name.downcase require file klass = const_get(name) return klass if klass raise "Class not found: #{name}" end
VALUE
rb_mod_const_missing(VALUE klass, VALUE name)
{
rb_frame_pop(); /* pop frame for "const_missing" */
uninitialized_constant(klass, rb_to_id(name));
return Qnil; /* not reached */
}
Sets the named constant to the given object, returning that object. Creates a new constant if no constant with the given name previously existed.
Math.const_set("HIGH_SCHOOL_PI", 22.0/7.0) #=> 3.14285714285714 Math::HIGH_SCHOOL_PI - Math::PI #=> 0.00126448926734968
static VALUE
rb_mod_const_set(VALUE mod, VALUE name, VALUE value)
{
ID id = rb_to_id(name);
if (!rb_is_const_id(id)) {
rb_name_error(id, "wrong constant name %s", rb_id2name(id));
}
rb_const_set(mod, id, value);
return value;
}
Returns an array of the names of the constants accessible in mod. This includes the names of constants in any included modules (example at start of section), unless the all parameter is set to false.
IO.constants.include?(:SYNC) #=> true IO.constants(false).include?(:SYNC) #=> false
Also see Module::const_defined?.
VALUE
rb_mod_constants(int argc, VALUE *argv, VALUE mod)
{
VALUE inherit;
st_table *tbl;
if (argc == 0) {
inherit = Qtrue;
}
else {
rb_scan_args(argc, argv, "01", &inherit);
}
if (RTEST(inherit)) {
tbl = rb_mod_const_of(mod, 0);
}
else {
tbl = rb_mod_const_at(mod, 0);
}
return rb_const_list(tbl);
}
Prevents further modifications to mod.
This method returns self.
static VALUE
rb_mod_freeze(VALUE mod)
{
rb_class_name(mod);
return rb_obj_freeze(mod);
}
Returns true if module is included in mod or one of mod’s ancestors.
module A end class B include A end class C < B end B.include?(A) #=> true C.include?(A) #=> true A.include?(A) #=> false
VALUE
rb_mod_include_p(VALUE mod, VALUE mod2)
{
VALUE p;
Check_Type(mod2, T_MODULE);
for (p = RCLASS_SUPER(mod); p; p = RCLASS_SUPER(p)) {
if (BUILTIN_TYPE(p) == T_ICLASS) {
if (RBASIC(p)->klass == mod2) return Qtrue;
}
}
return Qfalse;
}
Returns the list of modules included in mod.
module Mixin end module Outer include Mixin end Mixin.included_modules #=> [] Outer.included_modules #=> [Mixin]
VALUE
rb_mod_included_modules(VALUE mod)
{
VALUE ary = rb_ary_new();
VALUE p;
for (p = RCLASS_SUPER(mod); p; p = RCLASS_SUPER(p)) {
if (BUILTIN_TYPE(p) == T_ICLASS) {
rb_ary_push(ary, RBASIC(p)->klass);
}
}
return ary;
}
Returns an UnboundMethod representing the given instance method in mod.
class Interpreter def do_a() print "there, "; end def do_d() print "Hello "; end def do_e() print "!\n"; end def do_v() print "Dave"; end Dispatcher = { "a" => instance_method(:do_a), "d" => instance_method(:do_d), "e" => instance_method(:do_e), "v" => instance_method(:do_v) } def interpret(string) string.each_char {|b| Dispatcher[b].bind(self).call } end end interpreter = Interpreter.new interpreter.interpret('dave')
produces:
Hello there, Dave!
static VALUE
rb_mod_instance_method(VALUE mod, VALUE vid)
{
return mnew(mod, Qundef, rb_to_id(vid), rb_cUnboundMethod, FALSE);
}
Returns an array containing the names of the public and protected instance methods in the receiver. For a module, these are the public and protected methods; for a class, they are the instance (not singleton) methods. With no argument, or with an argument that is false, the instance methods in mod are returned, otherwise the methods in mod and mod’s superclasses are returned.
module A def method1() end end class B def method2() end end class C < B def method3() end end A.instance_methods #=> [:method1] B.instance_methods(false) #=> [:method2] C.instance_methods(false) #=> [:method3] C.instance_methods(true).length #=> 43
VALUE
rb_class_instance_methods(int argc, VALUE *argv, VALUE mod)
{
return class_instance_method_list(argc, argv, mod, 0, ins_methods_i);
}
Returns true if the named method is defined by mod (or its included modules and, if mod is a class, its ancestors). Public and protected methods are matched.
module A def method1() end end class B def method2() end end class C < B include A def method3() end end A.method_defined? :method1 #=> true C.method_defined? "method1" #=> true C.method_defined? "method2" #=> true C.method_defined? "method3" #=> true C.method_defined? "method4" #=> false
static VALUE
rb_mod_method_defined(VALUE mod, VALUE mid)
{
if (!rb_method_boundp(mod, rb_to_id(mid), 1)) {
return Qfalse;
}
return Qtrue;
}
Evaluates the string or block in the context of mod. This can be used to add methods to a class. module_eval returns the result of evaluating its argument. The optional filename and lineno parameters set the text for error messages.
class Thing end a = %q{def hello() "Hello there!" end} Thing.module_eval(a) puts Thing.new.hello() Thing.module_eval("invalid code", "dummy", 123)
produces:
Hello there! dummy:123:in `module_eval': undefined local variable or method `code' for Thing:Class
VALUE
rb_mod_module_eval(int argc, VALUE *argv, VALUE mod)
{
return specific_eval(argc, argv, mod, mod);
}
Evaluates the given block in the context of the class/module. The method defined in the block will belong to the receiver.
class Thing end Thing.class_exec{ def hello() "Hello there!" end } puts Thing.new.hello()
produces:
Hello there!
VALUE
rb_mod_module_exec(int argc, VALUE *argv, VALUE mod)
{
return yield_under(mod, mod, rb_ary_new4(argc, argv));
}
Returns the name of the module mod. Returns nil for anonymous modules.
VALUE
rb_mod_name(VALUE mod)
{
VALUE path = classname(mod);
if (!NIL_P(path)) return rb_str_dup(path);
return path;
}
Makes existing class methods private. Often used to hide the default constructor new.
class SimpleSingleton # Not thread safe private_class_method :new def SimpleSingleton.create(*args, &block) @me = new(*args, &block) if ! @me @me end end
static VALUE
rb_mod_private_method(int argc, VALUE *argv, VALUE obj)
{
set_method_visibility(CLASS_OF(obj), argc, argv, NOEX_PRIVATE);
return obj;
}
Returns a list of the private instance methods defined in mod. If the optional parameter is not false, the methods of any ancestors are included.
module Mod def method1() end private :method1 def method2() end end Mod.instance_methods #=> [:method2] Mod.private_instance_methods #=> [:method1]
VALUE
rb_class_private_instance_methods(int argc, VALUE *argv, VALUE mod)
{
return class_instance_method_list(argc, argv, mod, 0, ins_methods_priv_i);
}
Returns true if the named private method is defined by _ mod_ (or its included modules and, if mod is a class, its ancestors).
module A def method1() end end class B private def method2() end end class C < B include A def method3() end end A.method_defined? :method1 #=> true C.private_method_defined? "method1" #=> false C.private_method_defined? "method2" #=> true C.method_defined? "method2" #=> false
static VALUE
rb_mod_private_method_defined(VALUE mod, VALUE mid)
{
return check_definition(mod, rb_to_id(mid), NOEX_PRIVATE);
}
Returns a list of the protected instance methods defined in mod. If the optional parameter is not false, the methods of any ancestors are included.
VALUE
rb_class_protected_instance_methods(int argc, VALUE *argv, VALUE mod)
{
return class_instance_method_list(argc, argv, mod, 0, ins_methods_prot_i);
}
Returns true if the named protected method is defined by mod (or its included modules and, if mod is a class, its ancestors).
module A def method1() end end class B protected def method2() end end class C < B include A def method3() end end A.method_defined? :method1 #=> true C.protected_method_defined? "method1" #=> false C.protected_method_defined? "method2" #=> true C.method_defined? "method2" #=> true
static VALUE
rb_mod_protected_method_defined(VALUE mod, VALUE mid)
{
return check_definition(mod, rb_to_id(mid), NOEX_PROTECTED);
}
Makes a list of existing class methods public.
static VALUE
rb_mod_public_method(int argc, VALUE *argv, VALUE obj)
{
set_method_visibility(CLASS_OF(obj), argc, argv, NOEX_PUBLIC);
return obj;
}
Similar to instance_method, searches public method only.
static VALUE
rb_mod_public_instance_method(VALUE mod, VALUE vid)
{
return mnew(mod, Qundef, rb_to_id(vid), rb_cUnboundMethod, TRUE);
}
Returns a list of the public instance methods defined in mod. If the optional parameter is not false, the methods of any ancestors are included.
VALUE
rb_class_public_instance_methods(int argc, VALUE *argv, VALUE mod)
{
return class_instance_method_list(argc, argv, mod, 0, ins_methods_pub_i);
}
Returns true if the named public method is defined by mod (or its included modules and, if mod is a class, its ancestors).
module A def method1() end end class B protected def method2() end end class C < B include A def method3() end end A.method_defined? :method1 #=> true C.public_method_defined? "method1" #=> true C.public_method_defined? "method2" #=> false C.method_defined? "method2" #=> true
static VALUE
rb_mod_public_method_defined(VALUE mod, VALUE mid)
{
return check_definition(mod, rb_to_id(mid), NOEX_PUBLIC);
}
Removes the definition of the sym, returning that constant’s value.
class Dummy @@var = 99 puts @@var remove_class_variable(:@@var) p(defined? @@var) end
produces:
99 nil
VALUE
rb_mod_remove_cvar(VALUE mod, VALUE name)
{
const ID id = rb_to_id(name);
st_data_t val, n = id;
if (!rb_is_class_id(id)) {
rb_name_error(id, "wrong class variable name %s", rb_id2name(id));
}
if (!OBJ_UNTRUSTED(mod) && rb_safe_level() >= 4)
rb_raise(rb_eSecurityError, "Insecure: can't remove class variable");
if (OBJ_FROZEN(mod)) rb_error_frozen("class/module");
if (RCLASS_IV_TBL(mod) && st_delete(RCLASS_IV_TBL(mod), &n, &val)) {
return (VALUE)val;
}
if (rb_cvar_defined(mod, id)) {
rb_name_error(id, "cannot remove %s for %s",
rb_id2name(id), rb_class2name(mod));
}
rb_name_error(id, "class variable %s not defined for %s",
rb_id2name(id), rb_class2name(mod));
return Qnil; /* not reached */
}
Return a string representing this module or class. For basic classes and modules, this is the name. For singletons, we show information on the thing we’re attached to as well.
static VALUE
rb_mod_to_s(VALUE klass)
{
if (FL_TEST(klass, FL_SINGLETON)) {
VALUE s = rb_usascii_str_new2("#<");
VALUE v = rb_iv_get(klass, "__attached__");
rb_str_cat2(s, "Class:");
switch (TYPE(v)) {
case T_CLASS: case T_MODULE:
rb_str_append(s, rb_inspect(v));
break;
default:
rb_str_append(s, rb_any_to_s(v));
break;
}
rb_str_cat2(s, ">");
return s;
}
return rb_str_dup(rb_class_name(klass));
}