class UnboundMethod - ruby 4.1.0-preview1 documentation

Two unbound method objects are equal if they refer to the same method definition.

Array.instance_method(:each_slice) == Enumerable.instance_method(:each_slice)
#=> true

Array.instance_method(:sum) == Enumerable.instance_method(:sum)
#=> false, Array redefines the method for efficiency

#define unbound_method_eq method_eq

Also aliased as: eql?

arity → integer

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. Keyword arguments will be considered as a single additional argument, that argument being mandatory if any keyword argument is mandatory. 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
  def seven(a, b, x:0); end
  def eight(x:, y:); end
  def nine(x:, y:, **z); end
  def ten(*a, x:, y:); 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
c.method(:seven).arity   #=> -3
c.method(:eight).arity   #=> 1
c.method(:nine).arity    #=> 1
c.method(:ten).arity     #=> -2

"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(obj) → method

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)
{
    VALUE methclass, klass, iclass;
    const rb_method_entry_t *me;
    const struct METHOD *data;
    TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);
    convert_umethod_to_method_components(data, recv, &methclass, &klass, &iclass, &me, true);

    struct METHOD *bound;
    method = TypedData_Make_Struct(rb_cMethod, struct METHOD, &method_data_type, bound);
    RB_OBJ_WRITE(method, &bound->recv, recv);
    RB_OBJ_WRITE(method, &bound->klass, klass);
    RB_OBJ_WRITE(method, &bound->iclass, iclass);
    RB_OBJ_WRITE(method, &bound->owner, methclass);
    RB_OBJ_WRITE(method, &bound->me, me);

    return method;
}

bind_call(recv, args, ...) → obj

Bind umeth to recv and then invokes the method with the specified arguments. This is semantically equivalent to umeth.bind(recv).call(args, ...).

static VALUE
umethod_bind_call(int argc, VALUE *argv, VALUE method)
{
    rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);
    VALUE recv = argv[0];
    argc--;
    argv++;

    VALUE passed_procval = rb_block_given_p() ? rb_block_proc() : Qnil;
    rb_execution_context_t *ec = GET_EC();

    const struct METHOD *data;
    TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);

    const rb_callable_method_entry_t *cme = rb_callable_method_entry(CLASS_OF(recv), data->me->called_id);
    if (data->me == (const rb_method_entry_t *)cme) {
        vm_passed_block_handler_set(ec, proc_to_block_handler(passed_procval));
        return rb_vm_call_kw(ec, recv, cme->called_id, argc, argv, cme, RB_PASS_CALLED_KEYWORDS);
    }
    else {
        VALUE methclass, klass, iclass;
        const rb_method_entry_t *me;
        convert_umethod_to_method_components(data, recv, &methclass, &klass, &iclass, &me, false);
        struct METHOD bound = { recv, klass, 0, methclass, me };

        return call_method_data(ec, &bound, argc, argv, passed_procval, RB_PASS_CALLED_KEYWORDS);
    }
}

clone → new_method

Returns a clone of this method.

class A
  def foo
    return "bar"
  end
end

m = A.new.method(:foo)
m.call # => "bar"
n = m.clone.call # => "bar"

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(rb_obj_class(self), struct METHOD, &method_data_type, data);
    rb_obj_clone_setup(self, clone, Qnil);
    RB_OBJ_WRITE(clone, &data->recv, orig->recv);
    RB_OBJ_WRITE(clone, &data->klass, orig->klass);
    RB_OBJ_WRITE(clone, &data->iclass, orig->iclass);
    RB_OBJ_WRITE(clone, &data->owner, orig->owner);
    RB_OBJ_WRITE(clone, &data->me, rb_method_entry_clone(orig->me));
    return clone;
}

eql?(other_meth) → true or false

Two unbound method objects are equal if they refer to the same method definition.

Array.instance_method(:each_slice) == Enumerable.instance_method(:each_slice)
#=> true

Array.instance_method(:sum) == Enumerable.instance_method(:sum)
#=> false, Array redefines the method for efficiency

Alias for: ==

hash → integer

Returns a hash value corresponding to the method object.

See also Object#hash.

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->recv);
    hash = rb_hash_method_entry(hash, m->me);
    hash = rb_hash_end(hash);

    return ST2FIX(hash);
}

inspect → string

Returns a human-readable description of the underlying method.

"cat".method(:count).inspect   #=> "#<Method: String#count(*)>"
(1..3).method(:map).inspect    #=> "#<Method: Range(Enumerable)#map()>"

In the latter case, the method description includes the “owner” of the original method (Enumerable module, which is included into Range).

inspect also provides, when possible, method argument names (call sequence) and source location.

require 'net/http'
Net::HTTP.method(:get).inspect
#=> "#<Method: Net::HTTP.get(uri_or_host, path=..., port=...) <skip>/lib/ruby/2.7.0/net/http.rb:457>"

... in argument definition means argument is optional (has some default value).

For methods defined in C (language core and extensions), location and argument names can’t be extracted, and only generic information is provided in form of * (any number of arguments) or _ (some positional argument).

"cat".method(:count).inspect   #=> "#<Method: String#count(*)>"
"cat".method(:+).inspect       #=> "#<Method: String#+(_)>""

static VALUE
method_inspect(VALUE method)
{
    struct METHOD *data;
    VALUE str;
    const char *sharp = "#";
    VALUE mklass;
    VALUE defined_class;

    TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);
    str = rb_sprintf("#<% "PRIsVALUE": ", rb_obj_class(method));

    mklass = data->iclass;
    if (!mklass) mklass = data->klass;

    if (RB_TYPE_P(mklass, T_ICLASS)) {
        /* TODO: I'm not sure why mklass is T_ICLASS.
         * UnboundMethod#bind() can set it as T_ICLASS at convert_umethod_to_method_components()
         * but not sure it is needed.
         */
        mklass = RBASIC_CLASS(mklass);
    }

    if (data->me->def->type == VM_METHOD_TYPE_ALIAS) {
        defined_class = data->me->def->body.alias.original_me->owner;
    }
    else {
        defined_class = method_entry_defined_class(data->me);
    }

    if (RB_TYPE_P(defined_class, T_ICLASS)) {
        defined_class = RBASIC_CLASS(defined_class);
    }

    if (UNDEF_P(data->recv)) {
        // UnboundMethod
        rb_str_buf_append(str, rb_inspect(defined_class));
    }
    else if (RCLASS_SINGLETON_P(mklass)) {
        VALUE v = RCLASS_ATTACHED_OBJECT(mklass);

        if (UNDEF_P(data->recv)) {
            rb_str_buf_append(str, rb_inspect(mklass));
        }
        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 {
        mklass = data->klass;
        if (RB_TYPE_P(mklass, T_ICLASS)) {
            mklass = RBASIC_CLASS(mklass);
        }
        if (RCLASS_SINGLETON_P(mklass)) {
            VALUE v = RCLASS_ATTACHED_OBJECT(mklass);
            if (!(RB_TYPE_P(v, T_CLASS) || RB_TYPE_P(v, T_MODULE))) {
                do {
                   mklass = RCLASS_SUPER(mklass);
                } while (RB_TYPE_P(mklass, T_ICLASS));
            }
        }
        rb_str_buf_append(str, rb_inspect(mklass));
        if (defined_class != mklass) {
            rb_str_catf(str, "(% "PRIsVALUE")", defined_class);
        }
    }
    rb_str_buf_cat2(str, sharp);
    rb_str_append(str, rb_id2str(data->me->called_id));
    if (data->me->called_id != data->me->def->original_id) {
        rb_str_catf(str, "(%"PRIsVALUE")",
                    rb_id2str(data->me->def->original_id));
    }
    if (data->me->def->type == VM_METHOD_TYPE_NOTIMPLEMENTED) {
        rb_str_buf_cat2(str, " (not-implemented)");
    }

    // parameter information
    {
        VALUE params = rb_method_parameters(method);
        VALUE pair, name, kind;
        const VALUE req = ID2SYM(rb_intern("req"));
        const VALUE opt = ID2SYM(rb_intern("opt"));
        const VALUE keyreq = ID2SYM(rb_intern("keyreq"));
        const VALUE key = ID2SYM(rb_intern("key"));
        const VALUE rest = ID2SYM(rb_intern("rest"));
        const VALUE keyrest = ID2SYM(rb_intern("keyrest"));
        const VALUE block = ID2SYM(rb_intern("block"));
        const VALUE nokey = ID2SYM(rb_intern("nokey"));
        const VALUE noblock = ID2SYM(rb_intern("noblock"));
        int forwarding = 0;

        rb_str_buf_cat2(str, "(");

        if (RARRAY_LEN(params) == 3 &&
            RARRAY_AREF(RARRAY_AREF(params, 0), 0) == rest &&
            RARRAY_AREF(RARRAY_AREF(params, 0), 1) == ID2SYM('*') &&
            RARRAY_AREF(RARRAY_AREF(params, 1), 0) == keyrest &&
            RARRAY_AREF(RARRAY_AREF(params, 1), 1) == ID2SYM(idPow) &&
            RARRAY_AREF(RARRAY_AREF(params, 2), 0) == block &&
            RARRAY_AREF(RARRAY_AREF(params, 2), 1) == ID2SYM('&')) {
            forwarding = 1;
        }

        for (int i = 0; i < RARRAY_LEN(params); i++) {
            pair = RARRAY_AREF(params, i);
            kind = RARRAY_AREF(pair, 0);
            if (RARRAY_LEN(pair) > 1) {
                name = RARRAY_AREF(pair, 1);
            }
            else {
                name = Qnil;
            }

            if (kind == req) {
                append_param_name(str, name, "_");
            }
            else if (kind == opt) {
                rb_str_cat_cstr(append_param_name(str, name, "_"), "=...");
            }
            else if (kind == keyreq) {
                rb_str_cat_cstr(append_param_name(str, name, NULL), ":");
            }
            else if (kind == key) {
                rb_str_cat_cstr(append_param_name(str, name, NULL), ": ...");
            }
            else if (kind == rest) {
                rb_str_cat_cstr(str, forwarding ? "..." : "*");
                if (name != ID2SYM('*')) {
                    append_param_name(str, name, NULL);
                }
            }
            else if (kind == keyrest) {
                if (name != ID2SYM(idPow)) {
                    append_param_name(rb_str_cat_cstr(str, "**"), name, NULL);
                }
                else if (i > 0) {
                    rb_str_set_len(str, RSTRING_LEN(str) - 2);
                }
                else {
                    rb_str_cat_cstr(str, "**");
                }
            }
            else if (kind == block) {
                if (name == ID2SYM('&')) {
                    if (forwarding) {
                        rb_str_set_len(str, RSTRING_LEN(str) - 2);
                    }
                    else {
                        rb_str_cat_cstr(str, "...");
                    }
                }
                else {
                    append_param_name(rb_str_cat_cstr(str, "&"), name, NULL);
                }
            }
            else if (kind == nokey) {
                rb_str_buf_cat2(str, "**nil");
            }
            else if (kind == noblock) {
                rb_str_buf_cat2(str, "&nil");
            }

            if (i < RARRAY_LEN(params) - 1) {
                rb_str_buf_cat2(str, ", ");
            }
        }
        rb_str_buf_cat2(str, ")");
    }

    { // source location
        VALUE loc = rb_method_location(method);
        if (!NIL_P(loc)) {
            rb_str_catf(str, " %"PRIsVALUE":%"PRIsVALUE,
                        RARRAY_AREF(loc, 0), RARRAY_AREF(loc, 1));
        }
    }

    rb_str_buf_cat2(str, ">");

    return str;
}

Also aliased as: to_s

name → symbol

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->me->called_id);
}

original_name → symbol

Returns the original name of the method.

class C
  def foo; end
  alias bar foo
end
C.instance_method(:bar).original_name # => :foo

static VALUE
method_original_name(VALUE obj)
{
    struct METHOD *data;

    TypedData_Get_Struct(obj, struct METHOD, &method_data_type, data);
    return ID2SYM(data->me->def->original_id);
}

owner → class_or_module

Returns the class or module on which this method is defined. In other words,

meth.owner.instance_methods(false).include?(meth.name) # => true

holds as long as the method is not removed/undefined/replaced, (with private_instance_methods instead of instance_methods if the method is private).

See also Method#receiver.

(1..3).method(:map).owner #=> Enumerable

static VALUE
method_owner(VALUE obj)
{
    struct METHOD *data;
    TypedData_Get_Struct(obj, struct METHOD, &method_data_type, data);
    return data->owner;
}

parameters → array

Returns the parameter information of this method.

def foo(bar); end
method(:foo).parameters #=> [[:req, :bar]]

def foo(bar, baz, bat, &blk); end
method(:foo).parameters #=> [[:req, :bar], [:req, :baz], [:req, :bat], [:block, :blk]]

def foo(bar, *args); end
method(:foo).parameters #=> [[:req, :bar], [:rest, :args]]

def foo(bar, baz, *args, &blk); end
method(:foo).parameters #=> [[:req, :bar], [:req, :baz], [:rest, :args], [:block, :blk]]

static VALUE
rb_method_parameters(VALUE method)
{
    return method_def_parameters(rb_method_def(method));
}

source_location → location

Returns a two-element array containing the Ruby source filename as a string and the line number integer where self is defined:

def greeting = "hello"
method(:greeting).source_location # => ["test.rb", 1]

Returns nil if self is not a method defined in Ruby (i.e. defined using native code):

Kernel.method(:puts).source_location # => nil

VALUE
rb_method_location(VALUE method)
{
    return method_def_location(rb_method_def(method));
}

source_range → Ruby::SourceRange or nil

Returns a Ruby::SourceRange for this method, or nil if this method was not defined in Ruby (i.e. native) or has no source path.

The returned Ruby::SourceRange includes the source path, absolute path when available, and the start and end line and byte-column coordinates.

See github.com/ruby/spec/blob/master/core/method/shared/source_range.rb for the location of start/end line/column in various cases.

static VALUE
rb_method_source_range(VALUE method)
{
    return method_def_source_range(rb_method_def(method));
}

super_method → method

Returns a Method of superclass which would be called when super is used or nil if there is no method on superclass.

static VALUE
method_super_method(VALUE method)
{
    const struct METHOD *data;
    VALUE super_class, iclass;
    ID mid;
    const rb_method_entry_t *me;

    TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);
    iclass = data->iclass;
    if (!iclass) return Qnil;
    bool is_refinement_method = refinement_module_p(data->me->owner);
    if (data->me->def->type == VM_METHOD_TYPE_ALIAS && data->me->defined_class) {
        super_class = RCLASS_SUPER(rb_find_defined_class_by_owner(data->me->defined_class,
            data->me->def->body.alias.original_me->owner));
        mid = data->me->def->body.alias.original_me->def->original_id;
    }
    else if (is_refinement_method) {
        if (RICLASS_FOR_REFINEMENT_P(iclass)) {
            do {
                super_class = RCLASS_SUPER(iclass);
                iclass = super_class;
            } while (RICLASS_FOR_REFINEMENT_P(super_class));
        }
        else {
            super_class = find_refined_target_ancestor(iclass, rb_refinement_module_get_refined_class(data->me->owner));
            if (!super_class) {
                super_class = RCLASS_SUPER(data->me->owner);
            }
        }
        mid = data->me->def->original_id;
    }
    else {
        VALUE klass = iclass;
        if (RICLASS_FOR_REFINEMENT_P(klass)) {
            // Refined methods need this check before superclass determination
            klass = RBASIC(klass)->klass;
        }
        super_class = RCLASS_SUPER(RCLASS_ORIGIN(klass));
        mid = data->me->def->original_id;
    }
    if (!super_class) return Qnil;

    // For refined methods, skip refinements for the same definition, but consider
    // refinements for superclass methods
    const rb_method_definition_t *skip_def = is_refinement_method ? data->me->def : NULL;

    // Use the CREF of the Method/UnboundMethod, not the CREF of the caller of super_method.
    // We must avoid the use of rb_callable_method_entry_with_refinements, as that will
    // implicitly use the refinements activated in of the caller of super_method.
    const rb_cref_t *cref = NULL;
    switch (data->me->def->type) {
      case VM_METHOD_TYPE_ISEQ:
        cref = data->me->def->body.iseq.cref;
        break;
      case VM_METHOD_TYPE_BMETHOD: {
        const rb_proc_t *proc;
        GetProcPtr(data->me->def->body.bmethod.proc, proc);
        const struct rb_block *block = &proc->block;
        if (vm_block_type(block) == block_type_iseq)
            cref = rb_vm_get_cref(block->as.captured.ep);
        break;
      }
      default:
        break;
    }
    VALUE klass = super_class;
    me = NULL;
    while (klass) {
        const rb_callable_method_entry_t *cme = rb_callable_method_entry(klass, mid);
        if (!cme) break;
        if (cme->def->type != VM_METHOD_TYPE_REFINED) {
            me = (rb_method_entry_t *)cme;
            iclass = cme->defined_class;
            break;
        }
        // Look through all CREF scopes for a refinement for cme->owner, mirroring
        // the loop in search_refined_method.
        const rb_cref_t *c;
        for (c = cref; c; c = CREF_NEXT(c)) {
            VALUE refs = CREF_REFINEMENTS(c);
            if (NIL_P(refs)) continue;
            VALUE r = rb_hash_lookup(refs, cme->owner);
            if (NIL_P(r)) continue;
            r = rb_vm_refinement_iclass_for_cme(r, cme);
            const rb_callable_method_entry_t *ref_cme = rb_callable_method_entry(r, mid);
            if (!ref_cme) break;
            if (ref_cme->def->type == VM_METHOD_TYPE_REFINED) continue;
            if (skip_def && rb_method_definition_eq(ref_cme->def, skip_def)) continue;
            me = (rb_method_entry_t *)ref_cme;
            iclass = ref_cme->defined_class;
            break;
        }
        if (me) break;
        // No refined method found. Use orig_me if available, or normal method lookup
        // in superclass otherwise.
        const rb_method_entry_t *orig_me = cme->def->body.refined.orig_me;
        if (orig_me) {
            me = (rb_method_entry_t *)orig_me;
            iclass = cme->defined_class;
            break;
        }
        klass = RCLASS_SUPER(cme->defined_class);
    }
    if (!me) return Qnil;
    return mnew_internal(me, me->owner, iclass, data->recv, mid, rb_obj_class(method), FALSE, FALSE);
}

syntax_tree → Ruby::Prism::Node | RubyVM::AbstractSyntaxTree::Node | nil

Returns the AST node that this method was compiled from. Returns nil for methods not written in Ruby. See RubyVM::InstructionSequence#syntax_tree for other cases where nil is returned.

This method is experimental and might change without notice.

# File ast.rb, line 458
def syntax_tree
  RubyVM::InstructionSequence.of(self)&.syntax_tree
end

to_s → string

Returns a human-readable description of the underlying method.

"cat".method(:count).inspect   #=> "#<Method: String#count(*)>"
(1..3).method(:map).inspect    #=> "#<Method: Range(Enumerable)#map()>"

In the latter case, the method description includes the “owner” of the original method (Enumerable module, which is included into Range).

inspect also provides, when possible, method argument names (call sequence) and source location.

require 'net/http'
Net::HTTP.method(:get).inspect
#=> "#<Method: Net::HTTP.get(uri_or_host, path=..., port=...) <skip>/lib/ruby/2.7.0/net/http.rb:457>"

... in argument definition means argument is optional (has some default value).

For methods defined in C (language core and extensions), location and argument names can’t be extracted, and only generic information is provided in form of * (any number of arguments) or _ (some positional argument).

"cat".method(:count).inspect   #=> "#<Method: String#count(*)>"
"cat".method(:+).inspect       #=> "#<Method: String#+(_)>""

Alias for: inspect