![• No rules about what is stored in the array…
• No rules about how to store/retrieve…
• Often public…
• No separation of concerns…
• Arrays are by default passed byValue…
• Array[‘Notation’]…
WHATS WRONG WITH ARRAYS?](https://image.slidesharecdn.com/phpbelfast-collectionclasses-170517185921/85/PHP-Belfast-Collection-Classes-3-320.jpg)
![// the old way
Class Artist {
public $albums = array();
private $name;
public function __construct($name) {
$this->name = $name;
}
}
$artist = new Artist('Prince');
$artist->albums[] = '1999';
$artist->albums[] = 'Purple Rain';](https://image.slidesharecdn.com/phpbelfast-collectionclasses-170517185921/85/PHP-Belfast-Collection-Classes-11-320.jpg)
![Class Artist {
private $albums = array();
private $name;
public function __construct($name) {
$this->name = $name;
}
public function addItem($item) {
$this->albums[] = $item;
}
}
$artist = new Artist('Prince');
$artist->addItem[] = 'Purple Rain';](https://image.slidesharecdn.com/phpbelfast-collectionclasses-170517185921/85/PHP-Belfast-Collection-Classes-12-320.jpg)
![Class Artist {
/**
* @var AlbumCollection
*/
private $albums;
public function setAlbums($albums)
{
$this->albums = $albums;
}
//...
}
Class AlbumCollection {
private $items = array();
public function addItem(Album $album) {
$this->items[] = $album;
}
}](https://image.slidesharecdn.com/phpbelfast-collectionclasses-170517185921/85/PHP-Belfast-Collection-Classes-13-320.jpg)
![Class AlbumCollection implements IteratorAggregate ,
Countable {
private $items = array();
public function addItem(Album $album) {
$this->items[] = $album;
}
// Implement Traversable (Iterator Aggregate)
// Interface
public function getIterator() {
return new ArrayIterator($this->items);
}
// Implement Countable Interface
public function count() {
return count($this->items);
}
}](https://image.slidesharecdn.com/phpbelfast-collectionclasses-170517185921/85/PHP-Belfast-Collection-Classes-16-320.jpg)
![// An Artist has many Albums
Class AlbumCollection extends BaseCollection {
private $items = array();
public function addItem(Album $album) {
$this->items[] = $album;
}
}
// Albums have many Songs
Class SongCollection extends BaseCollection {
private $items = array();
public function addItem(Song $song) {
$this->items[] = $song;
}
}](https://image.slidesharecdn.com/phpbelfast-collectionclasses-170517185921/85/PHP-Belfast-Collection-Classes-19-320.jpg)
![Class AlbumCollection extends BaseCollection {
//…
}
// we can create an array of Albums
// or foreach through a DB powered list
$Albums[] = new Album('Batman');
$Albums[] = new Album('Purple Rain’);
$Albums[] = new Album('Dirty Mind');
$Albums[] = new Album('Diamonds and Pearls');
// this wont work
$collection = new AlbumCollection($Albums);
// this WILL work, using ‘…’ to unpack the Array
$collection = new AlbumCollection(…$Albums);](https://image.slidesharecdn.com/phpbelfast-collectionclasses-170517185921/85/PHP-Belfast-Collection-Classes-26-320.jpg)
PHP Belfast | Collection Classes
- 1. May the 4th PHP CollectionsImage by statefarm
- 2. • Object Relationships… • Perfect for One-To-Many Joins… • Traditionally just arrays which were good… WHY?
- 3. • No rules about what is stored in the array… • No rules about how to store/retrieve… • Often public… • No separation of concerns… • Arrays are by default passed byValue… • Array[‘Notation’]… WHATS WRONG WITH ARRAYS?
- 4. • Easy to use… • Easy to add, access, remove items… • Easy to traverse/loop… • How many array_ functions are there?… WHAT WAS RIGHT WITH ARRAYS?
- 5. • It’s a “bucket” of objects • So, essentially, it’s a wrapper for an array… • But encapsulated with rules… • We can control the indexes… • We know more about the content types… • It can have non-member properties WHAT IS A COLLECTION CLASS?
- 6. • private $items = array(); // property… • traversable… • countable… • Other Interfaces? e.g. JsonSerializable() or toJSON() ATTRIBUTES OF A COLLECTION CLASS
- 7. • Arrays are mutable… • Collection Classes are often mutable… • mutability is a choice to be made early on… • The Immutable class is lightweight… MUTABILITY
- 8. • with function addItem(FixedType $item){}… • we now have type checking • adding individual elements MUTABILITY &TYPE CHECKING
- 9. • Only one way an object can be immutable… • __construct($items){ $this->items = $items } • It is fixed after instantiation, no setItems / addItems methods… IMMUTABILITY &TYPE CHECKING
- 10. SOME CODE
- 11. // the old way Class Artist { public $albums = array(); private $name; public function __construct($name) { $this->name = $name; } } $artist = new Artist('Prince'); $artist->albums[] = '1999'; $artist->albums[] = 'Purple Rain';
- 12. Class Artist { private $albums = array(); private $name; public function __construct($name) { $this->name = $name; } public function addItem($item) { $this->albums[] = $item; } } $artist = new Artist('Prince'); $artist->addItem[] = 'Purple Rain';
- 13. Class Artist { /** * @var AlbumCollection */ private $albums; public function setAlbums($albums) { $this->albums = $albums; } //... } Class AlbumCollection { private $items = array(); public function addItem(Album $album) { $this->items[] = $album; } }
- 14. // Using the Collection Class $artist = new Artist('Prince'); // Build The Album Collection $albums = new AlbumCollection(); // Note we add Album types $albums->addItem( new Album('1999') ); $albums->addItem( new Album(‘Purple Rain') ); $albums->addItem( new Album(‘Sign O The Times') ); // Set the Collection as an Artist property $artist->setAlbums($albums);
- 16. Class AlbumCollection implements IteratorAggregate , Countable { private $items = array(); public function addItem(Album $album) { $this->items[] = $album; } // Implement Traversable (Iterator Aggregate) // Interface public function getIterator() { return new ArrayIterator($this->items); } // Implement Countable Interface public function count() { return count($this->items); } }
- 17. • Our app will contain more than one collection… • Remember DRY principles… • Don’t copy/paste the interface implementations… ABSTRACT FOR PORTABLITY
- 18. abstract Class BaseCollection implements Countable, IteratorAggregate { private $items = array(); // Implement Traversable via // IteratorAggregate Interface public function getIterator() { return new ArrayIterator($this->items); } // Implement Countable Interface public function count() { return count($this->items); } }
- 19. // An Artist has many Albums Class AlbumCollection extends BaseCollection { private $items = array(); public function addItem(Album $album) { $this->items[] = $album; } } // Albums have many Songs Class SongCollection extends BaseCollection { private $items = array(); public function addItem(Song $song) { $this->items[] = $song; } }
- 20. class Artist { // @var AlbumCollection protected $albums; // @var SongCollection protected $songs; // @var TourCollection protected $concerts; // MetadataCollection protected $metadata; // GenreCollection; protected $genres; // Tags Collection protected $tags; }
- 21. COLLECTING THE DOTS… WHAT ABOUTTHE DOTS..?
- 23. • Pass an indeterminate number of parameters… • Can pack a list of arguments… • Can unpack an array to a list of arguments… • Can be used in the function call or definition… • So… PHP5.6+ HASTHE …TOKEN THEVARIABLE LENGTHTOKEN bit.ly/VarL3nT0k
- 24. WITH IT WE CAN CREATE STRONGLY TYPED ARRAYS
- 25. Class AlbumCollection extends BaseCollection { private $items = array(); // Strongly typed, unknown length // All items passed must be of type Album public function __construct(Album ...$albums) { $this->items = $albums; } } $batman = new Album('Batman'); $purple = new Album('Purple Rain’); // this works, but it’s messy $albums = new AlbumCollection($batman, $purple);
- 26. Class AlbumCollection extends BaseCollection { //… } // we can create an array of Albums // or foreach through a DB powered list $Albums[] = new Album('Batman'); $Albums[] = new Album('Purple Rain’); $Albums[] = new Album('Dirty Mind'); $Albums[] = new Album('Diamonds and Pearls'); // this wont work $collection = new AlbumCollection($Albums); // this WILL work, using ‘…’ to unpack the Array $collection = new AlbumCollection(…$Albums);
- 27. • We are now portable thanks to our abstract collection • We are strongly typed • We are decoupled, each type and collection can be independently tested PORTABLE &TESTABLE
- 28. • IteratorAggregate Interface as a minimum • extend ArrayObject implements IteratorAggregate,ArrayAccess, Serializable, Countable • Only implement the functionality that you will use/need USETHE SPL…
- 29. • Add commonly used functionlaity to your base class • e.g. findBy($property, $value) BUILD ONYOUR BASE public function findBy($property, $value) { // look for an accessor method e.g. getTitle() $method = “get" . ucwords($property); foreach ($this->items as $key => $obj) { if (method_exists($obj, $method) { if ($obj->{$method}() == $property) { return($obj); } } } }
- 30. BUILD ONYOUR CONCRETE CLASS Class SongCollection extends BaseCollection { protected $items; // each song has a duration, // collection has a total duration private $totalDuration; public function getTotalDuration() { $totalDuration= 0; foreach($this->items as $song) { $totalDuration += $song->duration; } } }
- 31. • Many Frameworks, especially ORM components have their own Collection implementations • If you use a Framework investigate the options Doctrine ArrayCollection, IlluminateSupportCollection • If you aren’t using a framework… …Learn from the Frameworks A FINAL WORD ON FRAMEWORKS
- 32. T H A N K Y O U