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03.

Static or Non-Static Methods?

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In index.php, the three battle types are hard coded right in the HTML:

138 lines | index.php
// ... lines 1 - 29
<html>
// ... lines 31 - 55
<body>
<div class="container">
// ... lines 58 - 92
<div class="battle-box center-block border">
<div>
<form method="POST" action="/battle.php">
// ... lines 96 - 119
<div class="text-center">
<label for="battle_type">Battle Type</label>
<select name="battle_type" id="battle_type" class="form-control drp-dwn-width center-block">
<option value="<?php echo BattleManager::TYPE_NORMAL ?>">Normal</option>
<option value="<?php echo BattleManager::TYPE_NO_JEDI ?>">No Jedi Powers</option>
<option value="<?php echo BattleManager::TYPE_ONLY_JEDI ?>">Only Jedi Powers</option>
</select>
</div>
// ... lines 128 - 131
</form>
</div>
</div>
</div>
</body>
</html>

So what happens if we decide to add a fourth battle type to BattleManager. No problem: add a new constant, then update the battle() method logic for whatever cool thing this new type does.

But surprise! If we forget to also add the new type to index.php, then nobody's going to be able to use it. Really, I'd prefer BattleManager to be completely in charge of the battle types so that it's the only file I need to touch when something changes.

Using a Normal, Non-Static Method

To do that, create a new function in BattleManager that will return all of the types and their descriptions: call it public function getAllBattleTypesWithDescription():

92 lines | lib/Service/BattleManager.php
// ... lines 1 - 2
class BattleManager
{
// ... lines 5 - 75
public function getAllBattleTypesWithDescriptions()
{
// ... lines 78 - 82
}
// ... lines 84 - 90
}

Here, return an array with the type as the key and the description that should be used in the drop-down as the value:

92 lines | lib/Service/BattleManager.php
// ... lines 1 - 2
class BattleManager
{
// ... lines 5 - 75
public function getAllBattleTypesWithDescriptions()
{
return array(
self::TYPE_NORMAL => 'Normal',
self::TYPE_NO_JEDI => 'No Jedi Powers',
self::TYPE_ONLY_JEDI => 'Only Jedi Powers'
);
}
// ... lines 84 - 90
}

Awesome! Next, if we call this method in index.php, we can remove the hardcoded values there. Of course, this method is non-static. That means that we need to call this method on a BattleManager object. Create a new one by saying $battleManager = $container->getBattleManager():

141 lines | index.php
// ... lines 1 - 11
$battleManager = $container->getBattleManager();
// ... lines 13 - 141

Now add $battleTypes = $battleManager->getAllBattleTypesWithDescription():

141 lines | index.php
// ... lines 1 - 11
$battleManager = $container->getBattleManager();
$battleTypes = $battleManager->getAllBattleTypesWithDescriptions();
// ... lines 14 - 141

Finally, scroll down. In place of the hardcoded values, foreach over $battleTypes as $battleType => $typeText. End the foreach and make the option dynamic by printing $battleType and <?php echo $typeText; ?>:

141 lines | index.php
// ... lines 1 - 32
<html>
// ... lines 34 - 58
<body>
<div class="container">
// ... lines 61 - 95
<div class="battle-box center-block border">
<div>
<form method="POST" action="/battle.php">
// ... lines 99 - 122
<div class="text-center">
<label for="battle_type">Battle Type</label>
<select name="battle_type" id="battle_type" class="form-control drp-dwn-width center-block">
<?php foreach ($battleTypes as $battleType => $typeText): ?>
<option value="<?php echo $battleType ?>"><?php echo $typeText; ?></option>
<?php endforeach; ?>
</select>
</div>
// ... lines 131 - 134
</form>
</div>
</div>
</div>
</body>
</html>

Ok! Give it a try! Click the "Battle Again" link. And yes! The drop-down has the same three values as before.

Why not make the Method Static?

Here's where things get interesting! We made getAllBattleTypesWithDescription() non-static. Could we make it static instead?

To know, ask yourself these two questions:

  1. Does it make sense - philosphically - for the getAllBattleTypesWithDescription() method to be attached to the class instead an object? I would say yes: the battle types and descriptions will not be different for different BattleManager objects; these are global to the class.

  2. Does the method need the $this variable? If you need to reference non-static properties using $this, then the method must be non-static. But we're not using $this.

So let's make this method static by saying public static function:

92 lines | lib/Service/BattleManager.php
// ... lines 1 - 2
class BattleManager
{
// ... lines 5 - 75
public static function getAllBattleTypesWithDescriptions()
{
// ... lines 78 - 82
}
// ... lines 84 - 90
}

The only thing that changes now is how we call our method. First, we don't need a BattleManager object at all. Instead, just say BattleManager::getAllBattleTypesWithDescription():

140 lines | index.php
// ... lines 1 - 11
$battleTypes = BattleManager::getAllBattleTypesWithDescriptions();
// ... lines 13 - 140

Ok, try it out! It works!

When to use Static versus Non-Static

So look, this static versus non-static stuff can be tough. And in a lot of other tutorials, you'll see this taught in reverse: they'll show you static stuff first, because it's a little easier. Then they'll teach non-static properties and methods.

But guess what: that's not how good programmers code in the real world: they make most things non-static. And to start, I want you guys to also make everything not static. Then, as you get more comfortable, you will start to see different situations where it's okay to make some things static. It's actually much easier to change things from non-static to static than the other way around. And when you make things non-static, it forces you to build better code. And isn't that why we're here?