How to initialise an instance other than the current class in Ruby?

Question

I want to initialize instances of different class based on the initial params. For example, I want to have different behavior for Hello.new(true) and Hello.new(false) . Be precise, I want them to create instance of different classes .

How could I achieve that in Ruby?

class Name1
end

class Name2
end

class Hello
  def initialize(opts)
    if opts
      Name1.new
    else
      Name2.new
    end
  end
end

Answer 1

What you are talking about is called Factory pattern (at least, a simple version). It's possible to split the new process invoking allocate and initialize manually, but I don't recommend it.

The main reason is because it totally counter-intuitive. You'll (almost) never find a Ruby library behaving like this.

Instead, I suggest you to use a different method. For example, #factory .

class Name1
end

class Name2
end

class Hello
  def self.factory(opts)
    klass = if opts
      Name1
    else
      Name2
    end
    klass.new
  end
end

Hello.factory(...)