Question

In Ruby, a set can be initialized by Set[1,2,3]
So can an array: Array[1,2,3]

Is it possible to write some code to do the same thing to my own classes?
Or it’s just a language feature for only a few built-in classes?

Answer 1

In Ruby, foo[bar, baz] is just syntactic sugar for foo.[](bar, baz). All you need is a method named [].

By the way: you just need to look at the documentation, e.g. for Set:

[](*ary)

Creates a new set containing the given objects.

That’s the documentation right there.

Basically, all you need is

class Foo
  def self.[](*args, &block)
    new(*args, &block)
  end
end