Programming Ruby 3.3

A Metaprogramming Example

Let’s bring together all the metaprogramming topics we’ve discussed in a final example by writing a module that allows us to trace the execution of methods in any class that mixes the module in. This would let us write the following:

metaprogramming/trace_calls_example.rb

require_relative "trace_calls"

class Example
  def one(arg)
    puts "One called with #{arg}"
  end
end

ex1 = Example.new
ex1.one("Hello") # no tracing from this call

class Example
  include TraceCalls
  def two(arg1, arg2)
    arg1 + arg2
  end
end

ex1.one("Goodbye") # but we see tracing from these two
puts ex1.two(4, 5)

Produces:

One called with Hello
==> calling one with ["Goodbye"]