Projectionist

Method interception

class Module
  def intercept_method(method, temporary_result)
    original_method = "#{Time.now.to_i}_#{method}"
    alias_method original_method, method

    # Not enough room for a ternary ;_;
    t = if temporary_result.respond_to?(:to_proc)
      temporary_result.to_proc
    else
      Proc.new { temporary_result }
    end

    define_method(method, t)
    yield
    alias_method method, original_method
  end
end

class Duck; def quack; 'Quack!' end end

Duck.intercept_method(:quack, 'Honk!') do
  p Duck.new.quack
end
# => 'Honk!'
p Duck.new.quack
# => 'Quack!'