Method: UnboundMethod#bind

Defined in:

proc.c

#bind(obj) ⇒ Object

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

# File 'proc.c', line 2710

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;
}