PHP design pattern series-Iterator pattern (Iterator)

PHP design pattern series-Iterator pattern (Iterator) 1. Pattern Definition

The Iterator mode is also called the Cursor mode. Provides a method to access each element in a Container object without exposing the internal details of the object.

When you need to access an aggregate object and traverse all these objects, you should consider using the iterator mode. In addition, you can consider using the iterator mode when multiple aggregation methods are required. The iterator mode provides unified interfaces for traversing different clustering structures, such as start, next, end, and current.

The PHP Standard Library (SPL) provides the Iterator interface Iterator. to implement the Iterator mode, you can implement this interface.

2. UML class diagram

3. sample code Book. php

 author = $author;        $this->title = $title;    }    public function getAuthor()    {        return $this->author;    }    public function getTitle()    {        return $this->title;    }    public function getAuthorAndTitle()    {        return $this->getTitle() . ' by ' . $this->getAuthor();    }}

BookList. php

 books[$bookNumberToGet])) {            return $this->books[$bookNumberToGet];        }        return null;    }    public function addBook(Book $book)    {        $this->books[] = $book;    }    public function removeBook(Book $bookToRemove)    {        foreach ($this->books as $key => $book) {            /** @var Book $book */            if ($book->getAuthorAndTitle() === $bookToRemove->getAuthorAndTitle()) {                unset($this->books[$key]);            }        }    }    public function count()    {        return count($this->books);    }}

BookListIterator. php

 bookList = $bookList;    }    /**     * Return the current book     * @link http://php.net/manual/en/iterator.current.php     * @return Book Can return any type.     */    public function current()    {        return $this->bookList->getBook($this->currentBook);    }    /**     * (PHP 5 >= 5.0.0)
     * Move forward to next element     * @link http://php.net/manual/en/iterator.next.php     * @return void Any returned value is ignored.     */    public function next()    {        $this->currentBook++;    }    /**     * (PHP 5 >= 5.0.0)
     * Return the key of the current element     * @link http://php.net/manual/en/iterator.key.php     * @return mixed scalar on success, or null on failure.     */    public function key()    {        return $this->currentBook;    }    /**     * (PHP 5 >= 5.0.0)
     * Checks if current position is valid     * @link http://php.net/manual/en/iterator.valid.php     * @return boolean The return value will be casted to boolean and then evaluated.     *       Returns true on success or false on failure.     */    public function valid()    {        return null !== $this->bookList->getBook($this->currentBook);    }    /**     * (PHP 5 >= 5.0.0)
     * Rewind the Iterator to the first element     * @link http://php.net/manual/en/iterator.rewind.php     * @return void Any returned value is ignored.     */    public function rewind()    {        $this->currentBook = 0;    }}

BookListReverseIterator. php

 bookList = $bookList;        $this->currentBook = $this->bookList->count() - 1;    }    /**     * Return the current book     * @link http://php.net/manual/en/iterator.current.php     * @return Book Can return any type.     */    public function current()    {        return $this->bookList->getBook($this->currentBook);    }    /**     * (PHP 5 >= 5.0.0)
     * Move forward to next element     * @link http://php.net/manual/en/iterator.next.php     * @return void Any returned value is ignored.     */    public function next()    {        $this->currentBook--;    }    /**     * (PHP 5 >= 5.0.0)
     * Return the key of the current element     * @link http://php.net/manual/en/iterator.key.php     * @return mixed scalar on success, or null on failure.     */    public function key()    {        return $this->currentBook;    }    /**     * (PHP 5 >= 5.0.0)
     * Checks if current position is valid     * @link http://php.net/manual/en/iterator.valid.php     * @return boolean The return value will be casted to boolean and then evaluated.     *       Returns true on success or false on failure.     */    public function valid()    {        return null !== $this->bookList->getBook($this->currentBook);    }    /**     * (PHP 5 >= 5.0.0)
     * Rewind the Iterator to the first element     * @link http://php.net/manual/en/iterator.rewind.php     * @return void Any returned value is ignored.     */    public function rewind()    {        $this->currentBook = $this->bookList->count() - 1;    }}

4. test code Tests/IteratorTest. php

 bookList = new BookList();        $this->bookList->addBook(new Book('Learning PHP Design Patterns', 'William Sanders'));        $this->bookList->addBook(new Book('Professional Php Design Patterns', 'Aaron Saray'));        $this->bookList->addBook(new Book('Clean Code', 'Robert C. Martin'));    }    public function expectedAuthors()    {        return array(            array(                array(                    'Learning PHP Design Patterns by William Sanders',                    'Professional Php Design Patterns by Aaron Saray',                    'Clean Code by Robert C. Martin'                )            ),        );    }    /**     * @dataProvider expectedAuthors     */    public function testUseAIteratorAndValidateAuthors($expected)    {        $iterator = new BookListIterator($this->bookList);        while ($iterator->valid()) {            $expectedBook = array_shift($expected);            $this->assertEquals($expectedBook, $iterator->current()->getAuthorAndTitle());            $iterator->next();        }    }    /**     * @dataProvider expectedAuthors     */    public function testUseAReverseIteratorAndValidateAuthors($expected)    {        $iterator = new BookListReverseIterator($this->bookList);        while ($iterator->valid()) {            $expectedBook = array_pop($expected);            $this->assertEquals($expectedBook, $iterator->current()->getAuthorAndTitle());            $iterator->next();        }    }    /**     * Test BookList Remove     */    public function testBookRemove()    {        $this->bookList->removeBook($this->bookList->getBook(0));        $this->assertEquals($this->bookList->count(), 2);    }}