Tag Archives: clean code

An example of refactoring

As I have promised in my previous post, I would post an example of small refactorings in order to greatly improve the readability and understandability of code.

I own a little project called Dune II – The Maker, and I started writing it a little over 10 years ago. In those years I have learned a lot. I did not have much time in those days to apply my new knowledge to the project. You could say the software was rotting. In order to make it better I need to refactor a lot and I encounter the best examples to improve code without pointing fingers :). In any case I have experienced you have to make mistakes in order to get better. I hope you will learn from the mistakes I made.

So here is a little example I have just checked in the dune2themaker repository, I’ll give you the before (revision 411) and after (revision 412). Of course, I have taken smaller steps to get to the end result. First the original piece of code:

Revision 411 (before)
[sourcecode language=”cpp”]
void cGame::think_winlose() {
bool bSucces = false;
bool bFailed = true;

// determine if player is still alive
for (int i = 0; i < MAX_STRUCTURES; i++)
if (structure[i])
if (structure[i]->getOwner() == 0) {
bFailed = false; // no, we are not failing just yet
break;
}

// determine if any unit is found
if (bFailed) {
// check if any unit is ours, if not, we have a problem (airborn does not count)
for (int i = 0; i < MAX_UNITS; i++)
if (unit[i].isValid())
if (unit[i].iPlayer == 0) {
bFailed = false;
break;
}
}

// win by money quota
if (iWinQuota > 0) {
if (player[0].credits >= iWinQuota) {
// won!
bSucces = true;
}
} else {
// determine if any player (except sandworm) is dead
bool bAllDead = true;
for (int i = 0; i < MAX_STRUCTURES; i++)
if (structure[i])
if (structure[i]->getOwner() > 0 && structure[i]->getOwner()
!= AI_WORM) {
bAllDead = false;
break;
}

if (bAllDead) {
// check units now
for (int i = 0; i < MAX_UNITS; i++)
if (unit[i].isValid())
if (unit[i].iPlayer > 0 && unit[i].iPlayer != AI_WORM)
if (units[unit[i].iType].airborn == false) {
bAllDead = false;
break;
}

}

if (bAllDead)
bSucces = true;

}

// On succes…
if (bSucces) {
// <snip>

}

if (bFailed) {
// <snip>

}
}
[/sourcecode]

The intention of the think_winlose() function is to determine if the player has won or lost, and if so it transitions the game state. These transitions have been snipped.

So when does a player win or lose? It depends if there is a ‘win quota’, or not. The win quota is a number, whenever it is above zero it means the player has to collect at least that many of credits (spice) in order to win. If the win quota is not set, the default win rule : destroy everything of the enemy, will be used. (do you notice I need this much text for just a simple rule? Which I could have prevented If I had code that said this in the first place? At the bottom of this post you can see what I mean :))

Lets take a look at the code and point out what could be done better:

  • There are two booleans bSuccess and bFailed. Which is confusing and ambigious. What is succesfull? What did fail? Why aren’t they one boolean?
  • There are comments all over the place, meaning we could refactor these pieces to code so comments are not needed. (Comments are seen as clutter and should be removed)
  • The code formatting could be done better. If statements should start with { and end with }, even with one line.

And there are more things you will probably find yourself. What I’ll do is point out a few things that could be improved. If you just want to see the final result, just take a look below.

Lets start with the booleans bSuccess and bFailed. Why are there two booleans and whey are they called so vaguely? A little bit of searching in the code and we find out that bSuccess actually means “Mission is accomplished” (player has won), and bFailed means the player has no units and structures (which implicates the player has lost the game). They are not the same boolean, because a player could be alive and not have yet won the game of course. Now we know they are not actually the same boolean, but their naming was vague. A simple “rename variable” made things easier to understand!

[sourcecode language=”cpp”]
void cGame::think_winlose() {
bool bMissionAccomplished = false;
bool isPlayerAlive= true;
[/sourcecode]
(when posting this I realize the two booleans are named differently, consistency is also important to improve readability, so either both should start with “is” or both with a “b”, I prefer the first though)

Right after the booleans a few for loops are used just to find out if there is anything alive for the player. A little bit below we see such for loops again, but for the AI. This is duplicate code and should be removed. Extracting them into a method and make them return a boolean value is easy to do:

[sourcecode language=”cpp”]
bool cGame::playerHasAnyStructures(int iPlayerId) {
for (int i = 0; i < MAX_STRUCTURES; i++) {
if (structure[i]) {
if (structure[i]->getOwner() == iPlayerId) {
return true;
}
}
}
return false;
}
[/sourcecode]

(Again, while posting this I realize this could be even improved a bit more, the iPlayerId should be called ownerId (or the getOwner should be a getPlayerId), so it is obvious we match two of the same kind. Now it could confuse us: is an owner the same as the playerId? Since I know it is, why isn’t it called that way?… :))

Since we extract these for loops we can now set the isPlayerAlive boolean immidiately instead of setting a variable within the loop as it was done in the original example above. Reducing 24 lines into one!:

[sourcecode language=”cpp”]
bool isPlayerAlive = playerHasAnyStructures(HUMAN) || playerHasAnyGroundUnits(HUMAN);
[/sourcecode]

The final result of revision 412 is shown below. It will clearly show the major improvement regarding readability and understandability. Any other developer who comes to this code can see what it does and it is almost a no-brainer.

Result revision 412
[sourcecode language=”cpp”]
void cGame::think_winlose() {
bool bMissionAccomplished = false;
bool isPlayerAlive = playerHasAnyStructures(HUMAN) || playerHasAnyGroundUnits(HUMAN);

if (isWinQuotaSet()) {
bMissionAccomplished = playerHasMetQuota(HUMAN);
} else {
bool isAnyAIPlayerAlive = false;
for (int i = (HUMAN + 1); i < AI_WORM; i++ ) {
if (playerHasAnyStructures(i) || playerHasAnyGroundUnits(i)) {
isAnyAIPlayerAlive = true;
break;
}
}

bMissionAccomplished = !isAnyAIPlayerAlive;
}

if (bMissionAccomplished) {
// <snip>

} else if (!isPlayerAlive) {
// <snip>

}
}
[/sourcecode]