Record implementation in ruby

main.rb

relative_require "record"

class Record
  record :a, :b
end

a = Record.new(a: 10, b: 20)
a = a.merge(b: 10)
p a

record.rb

def record(*attrs)
  define_method('initialize') do |**args|
    attrs.each {|key| instance_variable_set("@#{key}", args[key])}
  end

  define_method('merge') do |**args|
    self.class.new **(instance_variables.map {|key| [key.slice(1).to_sym, instance_variable_get(key)]}.to_h.merge(args))
  end

  define_method('inspect') do ||
    data_format = instance_variables.map {|key| "#{key} = #{instance_variable_get(key)}"}.join(", ")
    "#{self.class.name}(#{data_format})"
  end

  attr_reader *attrs
end