class Method

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)>]

Public Instance Methods

meth << g → a_proc click to toggle source

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

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);
}

meth == other_meth → true or false click to toggle source

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.

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;
}

Also aliased as: eql?

===(*args)

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

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

Alias for: call

meth >> g → a_proc click to toggle source

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

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)

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

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

Alias for: call

arity → integer click to toggle source

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(*