MethodCop

method_cop.rb

module MethodCop
  # guard methods that have side effects with a callback that fires before the method is invoked. If the callback returns a "falsey" value,
  # the method is halted and will not be called. The callback will return nil instead.
  # if the method does not have side effects or you depend on its return value, you should NOT use this on that method!
  def guard_method(guarded_method, guard=nil, &callback)
    # normalize guard
    guard = method(guard) if guard.is_a?(Symbol)
    guard = callback if callback

    raise ArgumentError, "You can only supply either a guard argument or a block" if block && guard
    raise ArgumentError, "guard argument must respond to call" unless guard.respond_to?(:guard)

    original = method(guarded_method)
    define_method(guarded_method) do |*args, &block|
      original.call(*args, &block) if guard.call(*args, &block)
    end
  end
end

class Testing
  extend MethodCop
  def some_method
    return "I'm about to do something horribly wrong."
  end
  def run_method?
    # block everything
    return false
  end

  guard_method :some_method, :run_method?
  guard_method :some_method do false end
end