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Code to Multiple Interfaces
4:04Often when working with interfaces, you will be using existing interfaces such as the built-in Iterator interface. By combining multiple interfaces we can build powerful components that can be easily understood by the rest of our application.
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Now that we have some data to work with,
we want to create a collection that we can
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use for loops and
perform some additional functionalities.
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For the looping capabilities,
PHP offers us an iterator interface, so
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we don't need to create our own.
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Often, when working with interfaces,
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you will use existing interfaces
such as the iterator.
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Besides the interfaces
that are built into PHP,
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most frameworks include
their own interfaces.
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These interfaces work as a kind
of guaranteed documentation for
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using individual components.
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By combining multiple interfaces,
we can build powerful components
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that can be easily understood
by the rest of our application.
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Let's go back into our collection file.
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We are going to use implements Iterator.
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This implements the built
in iterator interface.
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This implements keyword is
how we specify that our class
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will meet the contract
of a given interface.
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We add the name of the interface and
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then it's up to us to implement
the details of that interface's methods.
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Somewhere in this class, I mentioned
that we can combine interfaces together
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to give our class more and
more capabilities.
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We can do that by adding more
interface names separated by comma.
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So for this example, we also want
the collection to be countable, so
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we can add a comma and
then the built-in Countable.
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We'll use two properties,
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protected $repo; and
a public $collection;.
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Then we'll set up a construct.
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On construct,
we're going to pass the $repo and
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optionally the ID and
field if we want to limit our collection.
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We don't care where the data is coming
from, but we do need to know that we can
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access the find and all methods that
we set up in our repository interface.
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Type declarations,
also called type hinting,
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allows us to require a specific
type of parameter on a method call.
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Type hinting for classes and
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interfaces was added in PHP5
along with arrays and callable.
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PHP7 added scaler type hints.
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These are the basic variable types of
Boolean, float, integer and string.
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To specify that our first parameter must
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implement the repository interface,
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we specify the name of
the interface before the parameter,
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public function __construct(
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RepositoryInterface, and then $repo,
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then we can add our optional parameters,
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$id = null, $field = 'id').
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On construct,
we first set the local $repo,
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then we populate our collection $this ->
repo = $repo; if the ID is not empty.
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Then we're going to say $this ->
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collection = $this->repo-> find(.
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We're going to past posts,
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the ID and the field.
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Else.
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$this->collection = $this->
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repo->all('posts');.
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Now we need to implement the methods from
the iterator and countable interfaces.
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