Is there simpler (one-line) syntax to alias one class method?

Question

I know I can do the following, and it's just 3 lines:

class << self
  alias :generate :new
end

But out of curiosity, is there a simpler way (without semicolons) like:

class_alias :generate, :new

Fun fact: `def self.generate; new; end` and `class_alias :generate, :new` are the same number of characters. — Amit Kumar Gupta, Feb 28 '13 at 08:52
@AmitKumarGupta That’s cheating, because `def self.generate; new; end` adds a redundant call on stack (not thta really matters, but to be as accurate as possible.) — Aleksei Matiushkin, Feb 28 '13 at 08:55
@AmitKumarGupta It also doesn't work if you need `new` to take any arguments. — Ajedi32, Aug 17 '13 at 22:42
IMHO your 3 lines read better than the 1 line accepted answer. — akostadinov, Jul 14 '15 at 09:06
The beauty of ruby is that its pretty easy to create your own dsl for anything. What's wrong with coding your `class_alias` I like it. — Michael K Madison, Sep 11 '19 at 17:47

Konrad Reiche · Accepted Answer · 2015-07-15T16:54:21.943

75

Since Ruby 1.9 you can use the singleton_class method to access the singleton object of a class. This way you can also access the alias_method method. The method itself is private so you need to invoke it with send. Here is your one liner:

singleton_class.send(:alias_method, :generate, :new)

Keep in mind though, that alias will not work here.

edited Jul 15 '15 at 16:54

answered Oct 10 '13 at 13:35

Konrad Reiche

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Small correction -- there is no need to prefix with `self.` – jaustin Jul 15 '15 at 16:39
@jaustin Thanks! Didn't realize, after all it's defined on `Object` – Konrad Reiche Jul 15 '15 at 16:54
Great solution! – Alexander Nov 11 '16 at 19:26
Beware: [alias and alias_method are not the same](https://github.com/rubocop-hq/ruby-style-guide#alias-method-lexically) – Jared Beck Dec 08 '18 at 02:48
1

That's neat!, thanks @KonradReiche I was using this way ``` class << self alias_method :open, :new end ``` – KING SABRI Dec 19 '18 at 21:11

score 7 · Answer 2 · answered Dec 12 '15 at 06:26

I am pasting some alias method examples

class Test
  def simple_method
    puts "I am inside 'simple_method' method"
  end

  def parameter_instance_method(param1)
    puts param1
  end

  def self.class_simple_method
    puts "I am inside 'class_simple_method'"
  end

  def self.parameter_class_method(arg)
    puts arg
  end


  alias_method :simple_method_new, :simple_method

  alias_method :parameter_instance_method_new, :parameter_instance_method

  singleton_class.send(:alias_method, :class_simple_method_new, :class_simple_method)
  singleton_class.send(:alias_method, :parameter_class_method_new, :parameter_class_method)
end

Test.new.simple_method_new
Test.new.parameter_instance_method_new("I am parameter_instance_method")

Test.class_simple_method_new
Test.parameter_class_method_new(" I am parameter_class_method")

OUTPUT

I am inside 'simple_method' method
I am parameter_instance_method
I am inside 'class_simple_method'
I am parameter_class_method

score 3 · Answer 3 · answered Aug 20 '13 at 07:41

I don't believe there is any class-specific version of alias. I usually use it as you have previously demonstrated.

However you may want to investigate the difference between alias and alias_method. This is one of those tricky areas of ruby that can be a bit counter-intuitive. In particular the behavior of alias with regard to descendants is probably not what you expect.

Hope this helps!

Is there simpler (one-line) syntax to alias one class method?

3 Answers3