confident_code.txt

Confident Code
Avdi Grimm
slides: http://avdi.org/talks/confident-code-railsconf-2011/

Look at Code Complete book.

um.

Narrative Structure:
  1. Gather Input
  2. Perform Work
  3. Deliver Results
  4. Handle Failure

Fewer branches and easier to understand, but NOT SHORTER. You know? That's okay.


GATHER INPUT
  Must be sure of your inputs.

  Switching (case) on the type of an object is a code smell (nil checks and
  try() count).

  With uncertain nput: coerce, reject or ignore.

  Coerce:
    to_s, to_i, to_sym, Array(), to_your_mom, etc.

    Look:
      Array([1, 2, 3]) #=> [1, 2, 3]
      Array("foo") #=> ["foo"]
      Array(nil) #=> []
      # woah!

    No consistent interface? Grab the Decorator pattern.

  Reject:
    Define an assert method that raises Exception.

    github.com/avdi/failfast

  Ignore:
    guard clause: return '' if input.nil?

    Special case? Make an object about it.
      def check_shit(status=$?)
        status ||= OpenScruct.new(:exitstatus => 0)

        unless [0, 172].include?(status.exitstatus)
          raise ArgumentError, "Command exited with status #{status.exitstatus}"
        end
      end

    Null Object: Returns self for any method call.
    Maybe(foo).bar.baz + buz # if foo.nil? this returns nil

    class Nothing
      def method_missing(*)
        self
      end

      def nil?; true; end
    end

    Maybe(value)
      value.nil? Nothing : value
    end

    use collection.fetch(key) { fallback_action }


PERFORM WORK
  Don't get distracted.

  Code what you mean.

  Conditionals raise cognative complexity; relegate them to business logic.

  Single object operations are inherantly 1-or-fail.

  Collection object operations are inherently 0-or-more.


DELIVER RESULTS
  Help your callers be confident (return NothingObject or special case object)


HANDLE FAILURE
  Put optimal path first; error handling at the end.

  bouncer method:
    def check_child_exit_status
      result = yield
      status = ? ... look for slides?
    end

  checked method:
    def checked_popen(command, mode, fail_action)
      check_child_ex... look for slides?
    end