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I'm in the midst of refactoring a project. I've recently read Clean Code, and want to heed some of the advice within, with particular interest in Single Responsibility Principle (SRP).

Currently, there's a class called OrderProcessor in the context of a manufacturing product order system.

This class is currently performs the following routine every n minutes:

  • check database for newly submitted + unprocessed orders (via a Data Layer class already, phew!)
  • gather all the details of the orders
  • mark them as in-process
  • iterate through each to:

    • perform some integrity checking
    • call a web service on a 3rd party system to place the order
    • check status return value of the web service for success/fail
    • email somebody if web service returns fail
  • constantly log to a text file on each operation or possible fail point

I've started by breaking out this class into new classes like:

  • OrderService - poor name. This is the one that wakes up every n minutes
  • OrderGatherer - calls the DL to get the order from the database
  • OrderIterator (? seems too forced or poorly named) -
  • OrderPlacer - calls web service to place the order
  • EmailSender
  • Logger

I'm struggling to find good names for each class, and implementing SRP in a reasonable way.

How could this class be separated into new class with discrete responsibilities?

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Now that you have used SRP concept, how do you plan to pass messages between those classes? Would this affect your performance? –  Emmad Kareem Sep 29 '12 at 19:01

1 Answer 1

As a general rule I have 1 class for every object (often linked to a DB table) or process.

It can sometimes be difficult to define all your classes ahead of time, so I tend to create some bare-bones classes and start writing a rough version (often procedural) of what I want to do. This process of actually seeing how your code hangs together enables me to start spotting patterns and links. I can then quickly change my skeleton classes quickly, effectively creating the design and workflow iteratively until I arrive at something I'm happy with.

I'd start with:

  1. OrderChecker - thread class that checks every n minutes
  2. OrderProcessor - gets new order from DB (using DAL) and processes each one - this is where the bulk of the work will take place, including making calls to EmailSender and Logger.
  3. OrderSender - Sends emails based on status of order (descended from generic email sender class)
  4. OrderLogger - Logs info based on results of order processing (descended from generic logger class?)

I find the key is to keep everything fairly "loose" (often quick-and-dirty) until you're happy with your design and have accounted for all foreseeable issues/requirements.

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