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<?php |
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/* |
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* Copyright (c) 2013 Janos Szurovecz |
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* |
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* Permission is hereby granted, free of charge, to any person obtaining a copy of |
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* this software and associated documentation files (the "Software"), to deal in |
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* the Software without restriction, including without limitation the rights to |
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* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies |
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* of the Software, and to permit persons to whom the Software is furnished to do |
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* so, subject to the following conditions: |
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* |
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* The above copyright notice and this permission notice shall be included in all |
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* copies or substantial portions of the Software. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE |
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* SOFTWARE. |
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*/ |
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namespace predaddy\presentation; |
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use ArrayIterator; |
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use IteratorAggregate; |
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use precore\lang\Object; |
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use precore\lang\ObjectInterface; |
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use precore\util\Objects; |
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/** |
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* Default Page implementation. |
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* |
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* @author Janos Szurovecz <[email protected]> |
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*/ |
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class PageImpl extends Object implements IteratorAggregate, Page |
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{ |
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private $content = []; |
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/** |
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* @var Pageable |
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*/ |
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private $pageable; |
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/** |
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* @var int |
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*/ |
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private $total; |
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/** |
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* @param array $content |
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* @param Pageable $pageable |
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* @param int $total Total number of all elements (not just the current page's) |
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*/ |
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public function __construct(array $content, Pageable $pageable = null, $total = null) |
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{ |
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$this->content = array_merge($this->content, $content); |
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$this->total = $total === null ? count($content) : $total; |
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$this->pageable = $pageable; |
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} |
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/** |
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* @return array of the records in the current page |
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*/ |
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public function getContent() |
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{ |
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return $this->content; |
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} |
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/** |
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* @return int The page number |
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*/ |
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public function getNumber() |
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{ |
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return $this->pageable === null |
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? 0 |
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: $this->pageable->getPageNumber(); |
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} |
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/** |
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* @return int size of the content |
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*/ |
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public function getSize() |
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{ |
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return $this->pageable === null |
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? 0 |
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: $this->pageable->getPageSize(); |
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} |
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public function getSort() |
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{ |
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return $this->pageable === null |
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? null |
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: $this->pageable->getSort(); |
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} |
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public function getTotalElements() |
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{ |
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return $this->total; |
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} |
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public function getTotalPages() |
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{ |
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return $this->getSize() == 0 |
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? 1 |
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: ceil($this->total / $this->getSize()); |
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} |
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public function hasContent() |
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{ |
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return count($this->content) !== 0; |
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} |
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public function hasNextPage() |
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{ |
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return $this->getNumber() + 1 < $this->getTotalPages(); |
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} |
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public function hasPreviousPage() |
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{ |
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return 0 < $this->getNumber(); |
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} |
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public function isFirstPage() |
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{ |
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return !$this->hasPreviousPage(); |
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} |
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public function isLastPage() |
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{ |
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return !$this->hasNextPage(); |
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} |
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/** |
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* Create a Pageable object to be able to obtain the next page. |
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* |
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* @return Pageable |
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*/ |
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public function nextPageable() |
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{ |
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return $this->hasNextPage() |
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? $this->pageable->next() |
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: null; |
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} |
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/** |
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* Create a Pageable object to be able to obtain the previous page. |
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* |
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* @return Pageable |
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*/ |
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public function previousPageable() |
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{ |
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return $this->hasPreviousPage() |
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? $this->pageable->previousOrFirst() |
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: null; |
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} |
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/** |
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* @return ArrayIterator|\Traversable |
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*/ |
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public function getIterator() |
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{ |
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return new ArrayIterator($this->content); |
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} |
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public function equals(ObjectInterface $object = null) |
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{ |
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if ($object === $this) { |
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return true; |
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} |
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/* @var $object PageImpl */ |
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return $object !== null |
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&& $this->getClassName() === $object->getClassName() |
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&& Objects::equal($this->total, $object->total) |
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&& Objects::equal($this->content, $object->content) |
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&& Objects::equal($this->pageable, $object->pageable); |
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} |
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public function toString() |
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{ |
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return Objects::toStringHelper($this) |
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->add('total', $this->total) |
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->add('pageable', $this->pageable) |
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->toString(); |
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} |
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} |
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If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_function
expects aPost
object, and outputs the author of the post. The base classPost
returns a simple string and outputting a simple string will work just fine. However, the child classBlogPost
which is a sub-type ofPost
instead decided to return anobject
, and is therefore violating the SOLID principles. If aBlogPost
were passed tomy_function
, PHP would not complain, but ultimately fail when executing thestrtoupper
call in its body.