PHP Service Classes

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  • 0:10
    PHP Service Classes with Leanna Pelham
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    It's time to put our new object- oriented skills into practice.
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    We're working on the same out-of-this-world project.
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    It has ships, you choose them, and they engage in epic battles!
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    In an editor far, far away,
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    you'll see a simple application that runs this.
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    Index.php is the home page,
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    and battle.php does the magic
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    and shows the results.
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    Last time, we created a single class called Ship,
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    which describes all its properties.
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    It's like a container for one ship's details.
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    We use these to replace these big associate of arrays.
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    Now we deal with cute ship objects.
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    Having a huge list of flat functions in functions.php
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    is not a good recipe for staying organized.
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    But in just a few minutes,
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    we'll use some new classes to give our app a whole new level of sophistication.
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    We'll get rid of battle first.
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    Look at Ship.
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    This is a class that basically just holds data.
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    Some people call that state, but I'll say data.
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    And I'm talking about the values on a ship object's properties.
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    So a ship object holds data,
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    but it doesn't really do any work.
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    Sure, it has some methods on it,
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    but these just return that data after doing some small logic at best.
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    Reason number one for creating a class is this:
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    we need some organized unit to hold data,
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    but there's a second big reason to create a class—
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    because you need to do some work.
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    For example, in functions.php,
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    the battle function does work.
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    We give it two ships, it does some calculations,
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    executes logic to see how different strengths affect each other,
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    and ultimately returns the result of that work.
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    And we're all familiar with creating functions like this.
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    Here's the secret for OO.
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    Whenever you get the urge to create a flat function like battle,
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    don't!
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    Instead, create a class with the method inside of it.
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    Let's do this!
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    Since this function is all about battling,
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    let's create a new class called BattleManager.
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    Be as creative as you want with naming.
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    I want to describe the methods in this class will do things related to battling.
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    Go copy and remove the flat battle function.
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    Paste it into BattleManager.
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    Put public in front of the function.
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    Remember, public means that code outside of this class
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    will be able to call this.
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    And yes, you don't have to add public,
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    functions default to public if you say nothing.
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    But let's keep things clear.
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    That's all you need to change.
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    Functions work the same inside or outside of a class.
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    They have arguments, they return stuff,
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    but we do need to change code where we call this function
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    in battle.php.
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    So how can we call this?
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    Well, when we want to call a method on Ship,
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    we need to have a ship object first.
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    The same is true here.
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    We need a BattleManager object first.
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    Start with a new variable called battleManager, and create a new BattleManager object.
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    And now say battleManager->battle.
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    Let's give this a shot.
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    Refresh battle.php.
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    Oh no! Class BattleManager not found!
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    Epic fail!
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    Not really!
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    At the top of functions.php, we have access to the Ship class
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    because we're requiring it.
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    Do the same for BattleManager.
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    There is a way where you can reference classes
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    like BattleManager without needing to worry about the require statements.
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    It's called auto loading.
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    It's really common, and you'll learn how to master it in a future episode.
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    But until then, if you have a class, require it.
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    Go back and refresh.
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    Cool! Totally working!
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    Now we have two reasons to create a class.
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    First, if you have some data
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    like properties that describe a ship,
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    creating a class for that is nice.
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    You'll create a Ship object whenever you have a set of that data.
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    In get_ships,
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    we create four ship objects.
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    These types of classes are sometimes called models
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    because they model something like a ship.
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    Second, if you need to make a function
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    that does some work, create a class and put a method in it
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    like BattleManager.
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    Or you may put multiple methods inside one class
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    as long as they're all thematically similar.
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    You'll create one of these objects like BattleManager
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    just one time before you need to call a method on it.
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    These are sometimes called service classes
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    because they perform work or a service.
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    Organizing your code to use service classes
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    can be tricky, but we'll learn all about that.
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PHP Service Classes

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In this series we're going to continue on from the Introduction to Object-Oriented PHP series. We're working on the same spaceship project: it has ships, you choose them, then they engage in epic battle!

In an editor, far far away, you'll see a simple application that runs this: index.php is the homepage and battle.php does the magic and shows the results. In the introduction series, we created a single class called Ship, which describes all its properties—it's like a container for one ship's details. In this tutorial we're going to replace our flat functions and create a BattleManager service class to provide the methods we'll need to do that.

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