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<?php |
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/** |
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* This script demonstrates how to keep entities in sync. |
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* Entities must have unique id, and the source and target must be ordered by this id. |
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* |
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* If entity is added into source then add callback is called |
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* If entity has been removed from source then remove callback is called |
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* If there is a change in entity data, then add and remove callbacks are called. |
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* |
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* It is not guaranteed that on update the remove callback is called before the add callback. |
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* The calling order depends on stringified source and target element comparison result. |
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* |
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* If it is important that on update the remove callback is called before the add callback |
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* (for example the id field index has unique constraints) then you have several options. |
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* |
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* One way is to gather all removals and additions into memory and process them later. |
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* This way you can detect if you need to insert, delete or update. |
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* |
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* Second one is to make add and remove callbacks more clever. |
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* |
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* Third one is to add last update date after the id in `__toString` method. But if you |
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* have already timestamp then you probably can use some better algorithm which does |
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* not require querying whole dataset ;) |
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* |
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* NB! Pay attention to the id in `__toString` method. The id is normalized so |
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* the stringified entities are ordered the same way as if they were |
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* ordered just by id. |
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*/ |
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require_once __DIR__ . '/../vendor/autoload.php'; |
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require_once __DIR__ . '/../tests/Stringable.php'; // polyfill for PHP 7 |
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/** |
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* An instance representing entity. |
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* This is what source and target iterator must return |
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* and add and remove callback will have as input. |
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*/ |
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class Entity implements Stringable |
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{ |
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public int $id; |
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public string $name; |
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public string $email; |
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/** |
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* @return string returns entity representation usable in strcmp function to compare with other entities. |
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*/ |
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public function __toString(): string |
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{ |
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// NB! NB! NB! The id must be in equal length! This way it is avoided |
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// that the lists order and entity order are not matching. |
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// For example, let's have two entities: id=1,name=B and id=10,name=A. |
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// After stringifing them we get "1B" and "10A". |
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// The next expression is valid and "10A" < "1B". |
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// But in iterator the 1 is before 10 and therefore the B is before the A. |
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$normalizedId = str_pad(strval($this->id), 5, "0", STR_PAD_RIGHT); |
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return $normalizedId |
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. $this->name |
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. $this->email; |
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} |
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public function __construct(int $id, string $name, string $email) |
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{ |
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$this->id = $id; |
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$this->name = $name; |
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$this->email = $email; |
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} |
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} |
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$synchronization = new \Raigu\OrderedListsSynchronization\Synchronization(); |
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$synchronization( |
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$source = new ArrayIterator([ |
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new Entity(1, 'John Doe', '[email protected]'), |
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new Entity(2, 'Jane Doe', '[email protected]'), |
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]), |
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$source = new ArrayIterator([ |
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new Entity(1, 'John Doe', '[email protected]'), |
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new Entity(2, 'Jane Doe', '[email protected]'), |
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]), |
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$add = function (Entity $element) { |
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echo "ADD: {$element->id} {$element->name} {$element->email}" . PHP_EOL; |
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}, |
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$remove = function (Entity $element) { |
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echo "REMOVE: {$element->id} {$element->name} {$element->email}" . PHP_EOL; |
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} |
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); |
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raigu /
ordered-lists-sync
