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instance method

Module#alias_method

(::interned new_name, ::interned old_name) -> ::Symbol

alias_method(new_name, old_name) → symbol

static VALUE
rb_mod_alias_method(VALUE mod, VALUE newname, VALUE oldname)
{
    ID oldid = rb_check_id(&oldname);
    if (!oldid) {
        rb_print_undef_str(mod, oldname);
    }
    VALUE id = rb_to_id(newname);
    rb_alias(mod, id, oldid);
    return ID2SYM(id);
}

Makes new_name a new copy of the method old_name. This can be used to retain access to methods that are overridden.

Example

class Greeter
  def hello
    "hello"
  end
  alias_method :orig_hello, :hello #=> :orig_hello
  def hello
    "#{orig_hello}, world"
  end
end
Greeter.new.hello #=> "hello, world"

In a module, old_name must be a method of the module or its ancestors. Aliasing a method found only through the fallback to Object is deprecated, and will raise a NameError in Ruby 4.3.

Ruby version changes

3.0
- Module#alias_method now returns the defined alias as a symbol. [Feature #17314]

See also #>= #ancestors #> #append_features also in 4.0 · 3.4 · 3.3 · 3.2 · 3.1 · 3.0

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