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Class: Method

Relationships & Source Files
Inherits: Object
Defined in: proc.c,
proc.c

Overview

Method objects are created by Object#method, and are associated with a particular object (not just with a class). They may be used to invoke the method within the object, and as a block associated with an iterator. They may also be unbound from one object (creating an ::UnboundMethod) and bound to another.

class Thing
  def square(n)
    n*n
  end
end
thing = Thing.new
meth  = thing.method(:square)

meth.call(9)                 #=> 81
[ 1, 2, 3 ].collect(&meth)   #=> [1, 4, 9]

[ 1, 2, 3 ].each(&method(:puts)) #=> prints 1, 2, 3

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)>]

Instance Method Summary

Instance Method Details

#<<(g) ⇒ Proc

Returns a proc that is the composition of this method and the given g. The returned proc takes a variable number of arguments, calls g with them then calls this method with the result.

def f(x)
  x * x
end

f = self.method(:f)
g = proc {|x| x + x }
p (f << g).call(2) #=> 16
[ GitHub ] 

  


# File 'proc.c', line 3839



static VALUE
rb_method_compose_to_left(VALUE self, VALUE g)
{
    g = to_callable(g);
    self = method_to_proc(self);
    return proc_compose_to_left(self, g);
}


  








  

    

      #eql?(other_meth)  ⇒ Boolean 
      #==(other_meth)  ⇒ Boolean 
    

    Also known as: #eql?
  



  

    

Two method objects are equal if they are bound to the same object and refer to the same method definition and the classes defining the methods are the same class or module.


  





  


  [ GitHub ]


  

  


# File 'proc.c', line 1788



static VALUE
method_eq(VALUE method, VALUE other)
{
    struct METHOD *m1, *m2;
    VALUE klass1, klass2;

    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 *)RTYPEDDATA_GET_DATA(method);
    m2 = (struct METHOD *)RTYPEDDATA_GET_DATA(other);

    klass1 = method_entry_defined_class(m1->me);
    klass2 = method_entry_defined_class(m2->me);

    if (!rb_method_entry_eq(m1->me, m2->me) ||
        klass1 != klass2 ||
        m1->klass != m2->klass ||
        m1->recv != m2->recv) {
        return Qfalse;
    }

    return Qtrue;
}


  








  

    

      #[](args, ...)  ⇒ Object 
      #===(args, ...)  ⇒ Object 
    

  



  

    

Alias for #[]. Invokes the method with obj as the parameter like #call. This allows a method object to be the target of a when clause in a case statement.



require 'prime'

case 1373
when Prime.method(:prime?)
  # ...
end


  





  








  

    #>>(g)  ⇒ Proc   



  

    

Returns a proc that is the composition of this method and the given g. The returned proc takes a variable number of arguments, calls this method with them then calls g with the result.



def f(x)
  x * x
end

f = self.method(:f)
g = proc {|x| x + x }
p (f >> g).call(2) #=> 8


  



  [ GitHub ]


  

  


# File 'proc.c', line 3863



static VALUE
rb_method_compose_to_right(VALUE self, VALUE g)
{
    g = to_callable(g);
    self = method_to_proc(self);
    return proc_compose_to_right(self, g);
}


  








  

    #[](args, ...)  ⇒ Object     Also known as: #call, #===
  



  

    

Invokes the meth with the specified arguments, returning the method’s return value.



m = 12.method("+")
m.call(3)    #=> 15
m.call(20)   #=> 32


  



  [ GitHub ]


  

  


# File 'proc.c', line 2474



static VALUE
rb_method_call_pass_called_kw(int argc, const VALUE *argv, VALUE method)
{
    return rb_method_call_kw(argc, argv, method, RB_PASS_CALLED_KEYWORDS);
}


  








  

    #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


  



  [ GitHub ]


  

  


# File 'proc.c', line 2852



static VALUE
method_arity_m(VALUE method)
{
    int n = method_arity(method);
    return INT2FIX(n);
}


  








  

    

      #[](args, ...)  ⇒ Object 
      #call(args, ...)  ⇒ Object 
    

  



  

    

Alias for #[].


  





  








  

    #clone  ⇒ 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"


  



  [ GitHub ]


  

  


# File 'proc.c', line 2396



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);
    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;
}


  








  

    

      #curry  ⇒ Proc 
      #curry(arity)  ⇒ Proc 
    

  



  

    

Returns a curried proc based on the method. When the proc is called with a number of arguments that is lower than the method’s arity, then another curried proc is returned. Only when enough arguments have been supplied to satisfy the method signature, will the method actually be called.



The optional arity argument should be supplied when currying methods with variable arguments to determine how many arguments are needed before the method is called.



def foo(a,b,c)
  [a, b, c]
end

proc  = self.method(:foo).curry
proc2 = proc.call(1, 2)          #=> #<Proc>
proc2.call(3)                    #=> [1,2,3]

def vararg(*args)
  args
end

proc = self.method(:vararg).curry(4)
proc2 = proc.call(:x)      #=> #<Proc>
proc3 = proc2.call(:y, :z) #=> #<Proc>
proc3.call(:a)             #=> [:x, :y, :z, :a]


  





  


  [ GitHub ]


  

  


# File 'proc.c', line 3683



static VALUE
rb_method_curry(int argc, const VALUE *argv, VALUE self)
{
    VALUE proc = method_to_proc(self);
    return proc_curry(argc, argv, proc);
}


  








  

    #dup  
  

  

    This method is for internal use only.
  

  [ GitHub ]


  

  


# File 'proc.c', line 2414



static VALUE
method_dup(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);
    rb_obj_dup_setup(self, clone);
    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)  ⇒ Boolean 
      #==(other_meth)  ⇒ Boolean 
    

  



  

    

Alias for #==.


  





  








  

    #hash  ⇒ Integer   



  

    

Returns a hash value corresponding to the method object.



See also Object#hash.


  



  [ GitHub ]


  

  


# File 'proc.c', line 1841



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);
}


  








  

    

      #to_s  ⇒ String 
      #inspect  ⇒ String 
    

  



  

    

Alias for #to_s.


  





  








  

    #name  ⇒ Symbol   



  

    

Returns the name of the method.


  



  [ GitHub ]


  

  


# File 'proc.c', line 1907



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


  



  [ GitHub ]


  

  


# File 'proc.c', line 1929



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 #receiver.



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


  



  [ GitHub ]


  

  


# File 'proc.c', line 1956



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]]


  



  [ GitHub ]


  

  


# File 'proc.c', line 3090



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


  








  

    #receiver  ⇒ Object   



  

    

Returns the bound receiver of the method object.



(1..3).method(:map).receiver # => 1..3


  



  [ GitHub ]


  

  


# File 'proc.c', line 1891



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

    TypedData_Get_Struct(obj, struct METHOD, &method_data_type, data);
    return data->recv;
}


  








  

    #source_location  ⇒ Array, Integer   



  

    

Returns the Ruby source filename and line number containing this method or nil if this method was not defined in Ruby (i.e. native).


  



  [ GitHub ]


  

  


# File 'proc.c', line 3002



VALUE
rb_method_location(VALUE method)
{
    return method_def_location(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.


  



  [ GitHub ]


  

  


# File 'proc.c', line 3378



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;
    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 {
        super_class = RCLASS_SUPER(RCLASS_ORIGIN(iclass));
        mid = data->me->def->original_id;
    }
    if (!super_class) return Qnil;
    me = (rb_method_entry_t *)rb_callable_method_entry_with_refinements(super_class, mid, &iclass);
    if (!me) return Qnil;
    return mnew_internal(me, me->owner, iclass, data->recv, mid, rb_obj_class(method), FALSE, FALSE);
}


  








  

    #to_proc  ⇒ Proc   



  

    

Returns a ::Proc object corresponding to this method.


  



  [ GitHub ]


  

  


# File 'proc.c', line 3347



static VALUE
method_to_proc(VALUE method)
{
    VALUE procval;
    rb_proc_t *proc;

    /*
     * class Method
     *   def to_proc
     *     lambda{|*args|
     *       self.call(*args)
     *     }
     *   end
     * end
     */
    procval = rb_block_call(rb_mRubyVMFrozenCore, idLambda, 0, 0, bmcall, method);
    GetProcPtr(procval, proc);
    proc->is_from_method = 1;
    return procval;
}


  








  

    

      #to_s  ⇒ String 
      #inspect  ⇒ String 
    

    Also known as: #inspect
  



  

    

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#+(_)>""


  





  


  [ GitHub ]


  

  


# File 'proc.c', line 3129



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 (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"));
        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);
            name = RARRAY_AREF(pair, 1);
            // FIXME: in tests it turns out that kind, name = [:req] produces name to be false. Why?..
            if (NIL_P(name) || name == Qfalse) {
                // FIXME: can it be reduced to switch/case?
                if (kind == req || kind == opt) {
                    name = rb_str_new2("_");
                }
                else if (kind == rest || kind == keyrest) {
                    name = rb_str_new2("");
                }
                else if (kind == block) {
                    name = rb_str_new2("block");
                }
                else if (kind == nokey) {
                    name = rb_str_new2("nil");
                }
            }

            if (kind == req) {
                rb_str_catf(str, "%"PRIsVALUE, name);
            }
            else if (kind == opt) {
                rb_str_catf(str, "%"PRIsVALUE"=...", name);
            }
            else if (kind == keyreq) {
                rb_str_catf(str, "%"PRIsVALUE":", name);
            }
            else if (kind == key) {
                rb_str_catf(str, "%"PRIsVALUE": ...", name);
            }
            else if (kind == rest) {
                if (name == ID2SYM('*')) {
                    rb_str_cat_cstr(str, forwarding ? "..." : "*");
                }
                else {
                    rb_str_catf(str, "*%"PRIsVALUE, name);
                }
            }
            else if (kind == keyrest) {
                if (name != ID2SYM(idPow)) {
                    rb_str_catf(str, "**%"PRIsVALUE, name);
                }
                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 {
                    rb_str_catf(str, "&%"PRIsVALUE, name);
                }
            }
            else if (kind == nokey) {
                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;
}


  








  

    #unbind  ⇒ Method   



  

    

Dissociates meth from its current receiver. The resulting ::UnboundMethod can subsequently be bound to a new object of the same class (see ::UnboundMethod).


  



  [ GitHub ]


  

  


# File 'proc.c', line 1864



static VALUE
method_unbind(VALUE obj)
{
    VALUE method;
    struct METHOD *orig, *data;

    TypedData_Get_Struct(obj, struct METHOD, &method_data_type, orig);
    method = TypedData_Make_Struct(rb_cUnboundMethod, struct METHOD,
                                   &method_data_type, data);
    RB_OBJ_WRITE(method, &data->recv, Qundef);
    RB_OBJ_WRITE(method, &data->klass, Qundef);
    RB_OBJ_WRITE(method, &data->iclass, orig->iclass);
    RB_OBJ_WRITE(method, &data->owner, orig->me->owner);
    RB_OBJ_WRITE(method, &data->me, rb_method_entry_clone(orig->me));

    return method;
}