Ruby supports two forms of objectified methods. Class Method is used to represent methods that are associated with a particular object: these method objects are bound to that object. Bound method objects for an object can be created using Object#method.
Ruby also supports unbound methods; methods objects that are not associated with a particular object. These can be created either by calling Module#instance_method or by calling unbind on a bound method object. The result of both of these is an UnboundMethod object.
Unbound methods can only be called after they are bound to an object. That object must be be a kind_of? the method’s original class.
class Square def area @side * @side end def initialize(side) @side = side end end area_un = Square.instance_method(:area) s = Square.new(12) area = area_un.bind(s) area.call #=> 144
Unbound methods are a reference to the method at the time it was objectified: subsequent changes to the underlying class will not affect the unbound method.
class Test def test :original end end um = Test.instance_method(:test) class Test def test :modified end end t = Test.new t.test #=> :modified um.bind(t).call #=> :original
Two method objects are equal if they are bound to the same object and refer to the same method definition.
static VALUE
method_eq(VALUE method, VALUE other)
{
struct METHOD *m1, *m2;
extern int rb_method_entry_eq(rb_method_entry_t *m1, rb_method_entry_t *m2);
if (!rb_obj_is_method(other))
return Qfalse;
if (CLASS_OF(method) != CLASS_OF(other))
return Qfalse;
Check_TypedStruct(method, &method_data_type);
m1 = (struct METHOD *)DATA_PTR(method);
m2 = (struct METHOD *)DATA_PTR(other);
if (!rb_method_entry_eq(&m1->me, &m2->me) ||
m1->rclass != m2->rclass ||
m1->recv != m2->recv) {
return Qfalse;
}
return Qtrue;
}
Returns an indication of the number of arguments accepted by a method. Returns a nonnegative integer for methods that take a fixed number of arguments. For Ruby methods that take a variable number of arguments, returns -n-1, where n is the number of required arguments. For methods written in C, returns -1 if the call takes a variable number of arguments.
class C def one; end def two(a); end def three(*a); end def four(a, b); end def five(a, b, *c); end def six(a, b, *c, &d); end end c = C.new c.method(:one).arity #=> 0 c.method(:two).arity #=> 1 c.method(:three).arity #=> -1 c.method(:four).arity #=> 2 c.method(:five).arity #=> -3 c.method(:six).arity #=> -3 "cat".method(:size).arity #=> 0 "cat".method(:replace).arity #=> 1 "cat".method(:squeeze).arity #=> -1 "cat".method(:count).arity #=> -1
static VALUE
method_arity_m(VALUE method)
{
int n = method_arity(method);
return INT2FIX(n);
}
Bind umeth to obj. If Klass was the class from which umeth was obtained, obj.kind_of?(Klass) must be true.
class A def test puts "In test, class = #{self.class}" end end class B < A end class C < B end um = B.instance_method(:test) bm = um.bind(C.new) bm.call bm = um.bind(B.new) bm.call bm = um.bind(A.new) bm.call
produces:
In test, class = C In test, class = B prog.rb:16:in `bind': bind argument must be an instance of B (TypeError) from prog.rb:16
static VALUE
umethod_bind(VALUE method, VALUE recv)
{
struct METHOD *data, *bound;
TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);
if (data->rclass != CLASS_OF(recv) && !rb_obj_is_kind_of(recv, data->rclass)) {
if (FL_TEST(data->rclass, FL_SINGLETON)) {
rb_raise(rb_eTypeError,
"singleton method called for a different object");
}
else {
rb_raise(rb_eTypeError, "bind argument must be an instance of %s",
rb_class2name(data->rclass));
}
}
method = TypedData_Make_Struct(rb_cMethod, struct METHOD, &method_data_type, bound);
*bound = *data;
if (bound->me.def) bound->me.def->alias_count++;
bound->recv = recv;
bound->rclass = CLASS_OF(recv);
return method;
}
MISSING: documentation
static VALUE
method_clone(VALUE self)
{
VALUE clone;
struct METHOD *orig, *data;
TypedData_Get_Struct(self, struct METHOD, &method_data_type, orig);
clone = TypedData_Make_Struct(CLASS_OF(self), struct METHOD, &method_data_type, data);
CLONESETUP(clone, self);
*data = *orig;
if (data->me.def) data->me.def->alias_count++;
return clone;
}
Two method objects are equal if they are bound to the same object and refer to the same method definition.
static VALUE
method_eq(VALUE method, VALUE other)
{
struct METHOD *m1, *m2;
extern int rb_method_entry_eq(rb_method_entry_t *m1, rb_method_entry_t *m2);
if (!rb_obj_is_method(other))
return Qfalse;
if (CLASS_OF(method) != CLASS_OF(other))
return Qfalse;
Check_TypedStruct(method, &method_data_type);
m1 = (struct METHOD *)DATA_PTR(method);
m2 = (struct METHOD *)DATA_PTR(other);
if (!rb_method_entry_eq(&m1->me, &m2->me) ||
m1->rclass != m2->rclass ||
m1->recv != m2->recv) {
return Qfalse;
}
return Qtrue;
}
Return a hash value corresponding to the method object.
static VALUE
method_hash(VALUE method)
{
struct METHOD *m;
st_index_t hash;
TypedData_Get_Struct(method, struct METHOD, &method_data_type, m);
hash = rb_hash_start((st_index_t)m->rclass);
hash = rb_hash_uint(hash, (st_index_t)m->recv);
hash = rb_hash_uint(hash, (st_index_t)m->me.def);
hash = rb_hash_end(hash);
return INT2FIX(hash);
}
Show the name of the underlying method.
"cat".method(:count).inspect #=> "#<Method: String#count>"
static VALUE
method_inspect(VALUE method)
{
struct METHOD *data;
VALUE str;
const char *s;
const char *sharp = "#";
TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);
str = rb_str_buf_new2("#<");
s = rb_obj_classname(method);
rb_str_buf_cat2(str, s);
rb_str_buf_cat2(str, ": ");
if (FL_TEST(data->me.klass, FL_SINGLETON)) {
VALUE v = rb_iv_get(data->me.klass, "__attached__");
if (data->recv == Qundef) {
rb_str_buf_append(str, rb_inspect(data->me.klass));
}
else if (data->recv == v) {
rb_str_buf_append(str, rb_inspect(v));
sharp = ".";
}
else {
rb_str_buf_append(str, rb_inspect(data->recv));
rb_str_buf_cat2(str, "(");
rb_str_buf_append(str, rb_inspect(v));
rb_str_buf_cat2(str, ")");
sharp = ".";
}
}
else {
rb_str_buf_cat2(str, rb_class2name(data->rclass));
if (data->rclass != data->me.klass) {
rb_str_buf_cat2(str, "(");
rb_str_buf_cat2(str, rb_class2name(data->me.klass));
rb_str_buf_cat2(str, ")");
}
}
rb_str_buf_cat2(str, sharp);
rb_str_append(str, rb_id2str(data->me.def->original_id));
if (data->me.def->type == VM_METHOD_TYPE_NOTIMPLEMENTED) {
rb_str_buf_cat2(str, " (not-implemented)");
}
rb_str_buf_cat2(str, ">");
return str;
}
Returns the name of the method.
static VALUE
method_name(VALUE obj)
{
struct METHOD *data;
TypedData_Get_Struct(obj, struct METHOD, &method_data_type, data);
return ID2SYM(data->id);
}
Returns the class or module that defines the method.
static VALUE
method_owner(VALUE obj)
{
struct METHOD *data;
TypedData_Get_Struct(obj, struct METHOD, &method_data_type, data);
return data->me.klass;
}
returns the parameter information of this method
static VALUE
rb_method_parameters(VALUE method)
{
rb_iseq_t *iseq = rb_method_get_iseq(method);
if (!iseq) {
return unnamed_parameters(method_arity(method));
}
return rb_iseq_parameters(iseq, 0);
}
returns the ruby source filename and line number containing this method or nil if this method was not defined in ruby (i.e. native)
VALUE
rb_method_location(VALUE method)
{
rb_method_definition_t *def = method_get_def(method);
if (def->type == VM_METHOD_TYPE_ATTRSET || def->type == VM_METHOD_TYPE_IVAR) {
if (!def->body.attr.location)
return Qnil;
return rb_ary_dup(def->body.attr.location);
}
return iseq_location(method_get_iseq(def));
}
Show the name of the underlying method.
"cat".method(:count).inspect #=> "#<Method: String#count>"
static VALUE
method_inspect(VALUE method)
{
struct METHOD *data;
VALUE str;
const char *s;
const char *sharp = "#";
TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);
str = rb_str_buf_new2("#<");
s = rb_obj_classname(method);
rb_str_buf_cat2(str, s);
rb_str_buf_cat2(str, ": ");
if (FL_TEST(data->me.klass, FL_SINGLETON)) {
VALUE v = rb_iv_get(data->me.klass, "__attached__");
if (data->recv == Qundef) {
rb_str_buf_append(str, rb_inspect(data->me.klass));
}
else if (data->recv == v) {
rb_str_buf_append(str, rb_inspect(v));
sharp = ".";
}
else {
rb_str_buf_append(str, rb_inspect(data->recv));
rb_str_buf_cat2(str, "(");
rb_str_buf_append(str, rb_inspect(v));
rb_str_buf_cat2(str, ")");
sharp = ".";
}
}
else {
rb_str_buf_cat2(str, rb_class2name(data->rclass));
if (data->rclass != data->me.klass) {
rb_str_buf_cat2(str, "(");
rb_str_buf_cat2(str, rb_class2name(data->me.klass));
rb_str_buf_cat2(str, ")");
}
}
rb_str_buf_cat2(str, sharp);
rb_str_append(str, rb_id2str(data->me.def->original_id));
if (data->me.def->type == VM_METHOD_TYPE_NOTIMPLEMENTED) {
rb_str_buf_cat2(str, " (not-implemented)");
}
rb_str_buf_cat2(str, ">");
return str;
}