A Ruby Struct, but with a keyword argument constructor, allowing for optional parameters

kwarg_struct.rb

class KwargsStruct < Struct
  def initialize(*args, **kwargs)
    # assumes the keyword argument takes priority
    super *members.each_with_index.map { |k, i| kwargs[k] || args[i] }
  end
end

> KS = KwargsStruct.new(:a, :b, :c)
=> KS

# kwargs-only
> KS.new(a: 1, c: 3)
=> #<struct KS a=1, b=nil, c=3>

# combined args and kwargs
> ks = KS.new(2, 5, c: 3)
=> #<struct KS a=2, b=5, c=3>

# combined args and kwargs, with keyword priority
> ks = KS.new(2, a: 1, c: 3)
=> #<struct KS a=1, b=nil, c=3>

nevermind, I just learned about Struct's keyword_init:

KS = Struct.new(:a, :b, :c, keyword_init: true)

> KS.new(a: 1, c: 3)
=> #<struct KS a=1, b=nil, c=3>