How to replace a string with hash in ruby, using .gsubs?

I just started learning Ruby and I need to create a template where it replace my strings with hashes that I write. What I need to add in my code?

This is my code, I write two methods for my task, help please with your suggestions

  def initialize(template_string, local_variables)
   @template_string = template_string
   @local_variables = local_variables
end 

  def compile()
  @template_string.gsub()
end
end



puts Template.new("I like %{x}", x:"coffee").compile # x = coffee
puts Template.new("x = %{x}", y:5).compile # unknown x
puts Template.new("x = %{x}", x:5, y:3).compile # x = 5, ignores y