piątek, 26 grudnia 2014

Your code sucks - things you need to know about clean code and architecture

 Although the title is an exaggeration, all code I've seen in my (short) professional career did indeed suck. Because it's my first post, it'd be appropriate to talk about something very important to me: code quality

I want this post to be something of a quick collection of references for programmers on how can they recognize if their code sucks and how should they try to fix it. I'll avoid getting into details or code examples.

I'd like to say it's targeted to junior programmers, but I know for a fact that there are some senior programmers out there that didn't hear of such basic concepts as Dependency injection or Don't-Repeat-Yourself principle.

Clean up your code, would you ?

I wish I ruled the world and that's just for one selfish reason: force all programmers to read this book. If all developers followed the simple rules described in Clean Code by Robert C. Martin the IT world would be so much nicer.

It would most definitely prevent such classes as Start from being created. It's actually a pretty decent one compared to some other classes on the repo of Polish Electoral Calculator client, which is only... one of the most important programs in the country. 

There are a few basic rules a decent developer should follow:

  • Replace comments with meaningful method/variable names. 
    Code should comment itself
  • Methods should do one thing and one thing only
  • Methods should be very short 
    If a method is longer than 10-30 lines, consider dividing it into separate methods
  • Don't keep dead code - your repo is your history, not commented code
  • Don't use magic strings and magic numbers
    The only exception I use are log and error mesage strings. It would be tiresome to create a constant for every possible log.
  • If a class is very long, consider dividing it
  • Don't use snake expressions
    If one expression is long, divide it into several different expressions
  • Don't repeat yourself
    If you have two blocks of similiar looking code, it means it probably needs to be put in one method
And probably many more I missed. The point here is: if you didn't know about at least one of these rules, that's more the reason to browse through the book.

My two cents

I find comments and macros very useful when it comes to arranging insides of your file. 

I like to keep my private methods and public methods divided by comments/macros.

I also put comments before every method to put method/parameters/return information for documentation (check out automatic documentation generators for IDE you're using, to see what format to use) and put a clear sign that "this method starts here". When you open the DOOM 3 source files you immediately notice when methods start. Actually, DOOM3 source code is pretty good example of clean code, here's a good blog post about that:" The exceptional bueaty of DOOM 3`s source code".

“Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live.” - Someone

Design Patterns

If you're a developer and you've never heard of design patterns, well then better hurry: click.
Even if you find out that you don't like to use design patterns, you have to know them by heart. Why? It has an undeniable advantage: it's a universal language of software architecture.

You are the architect

Your classes are your blocks, your program is your city. The bigger the city, the better architect you have to be to prevent the city from falling apart.

Architecture is a huge chunk of computer software. It's not something you learn in a short blog post. It's also unique for every programming language or kind of program. But hey, we can always cover some basics, right ?

The most basic thing you need to follow is:

 Keep your program modular (loosely coupled)

It's easier to look at a program that's just simple modules talking to each other, than a growing spaghetti monster. It's also easier to switch stuff around.


Let's say you have a Client class that uses a SQLite Database object to write and read from that database. One day your project manager tells you that SQLite sucks and he wants to to write and read to a file instead.


How can we switch writing to database to writing to a file ? They seem like two very distant things. Yeah, but they have something in common, they're both writing to some local storage. Let's make an interface/protocol/abstract class LocalStorage. Make SQLiteImplementation, and FileReadWriteImplementation, conform to this interface and make the Client talk to LocalStorage object. It explains a one simple rule:

 Always separate your interface, from your concrete classes if you have more than one implementation.

It's done using a simple design pattern called Bridge, or Strategy. They're the same thing implementation-wise but have different uses. 


How can we tell the Client which implementation to use ? Doesn't the Client create his own LocalStorage objects ? Well, it does, if the code is tightly coupled. 

In a perfect scenario, something from outside tells the Client which local storage to use. It's called Inversion of Control and the most popular implementation of that principle is Dependency Injection. We inject (tell the Client) the dependencies (Client depends on the database) to the class. Which brings us to our next rule:

 Use Dependency Injection (IoC)

It makes code highly reusable, losely coupled, easy to test, plus it has a great advantage while creating Unit Tests.

A little extra: Using mocks in unit testing

How do you write unit tests for server calls? Calls to databases without actually connecting to one ? Or how do you unit test if you still haven't finished some modules ? It's easy if you're using Dependency Injection.

Let's say we want to test our Client but we don't have access to the database. Just create a class LocalStorageMockImplementation that extends the LocalStorage interface and inject that class into the Client. Now you can test your client properly. Here's a quick tutorial if you want to know more.

Let it sink in

In my opinion, these are the basics that every developer should know, before writing a single line of code. It's not a lot to take in, and by sticking to these rules, you create a readable, highly reusable, changeable code - a miracle I have yet to experience.