Method: Object#dup

Defined in:

object.c

#dup ⇒ Object

Produces a shallow copy of obj—the instance variables of obj are copied, but not the objects they reference.

This method may have class-specific behavior. If so, that behavior will be documented under the #initialize_copy method of the class.

on dup vs clone

In general, #clone and #dup may have different semantics in descendant classes. While #clone is used to duplicate an object, including its internal state, #dup typically uses the class of the descendant object to create the new instance.

When using #dup, any modules that the object has been extended with will not be copied.

class Klass

attr_accessor :str

end

module Foo

def foo; 'foo'; end

end

s1 = Klass.new #=> #<Klass:0x401b3a38> s1.extend(Foo) #=> #<Klass:0x401b3a38> s1.foo #=> “foo”

s2 = s1.clone #=> #<Klass:0x401be280> s2.foo #=> “foo”

s3 = s1.dup #=> #<Klass:0x401c1084> s3.foo #=> NoMethodError: undefined method ‘foo’ for #<Klass:0x401c1084>

Returns:

• (Object)

# File 'object.c', line 558

VALUE
rb_obj_dup(VALUE obj)
{
    VALUE dup;

    if (special_object_p(obj)) {
	return obj;
    }
    dup = rb_obj_alloc(rb_obj_class(obj));
    init_copy(dup, obj);
    rb_funcall(dup, id_init_dup, 1, obj);

    return dup;
}