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Blog Tutorial - Part 3

Create a Tree Category

Let’s continue our blog application and imagine we want to categorize our articles. We want the categories to be ordered, and for this, we will use the Tree behavior to help us organize the categories.

But first, we need to modify our tables.

Migrations Plugin

We will use the migrations plugin to create a table in our database. If you already have an articles table in your database, erase it.

Now open your application’s composer.json file. Normally you would see that the migrations plugin is already under require. If not, add it by executing:

composer require cakephp/migrations:~1.0

The migrations plugin will now be in your application’s plugins folder. Also, add $this->addPlugin('Migrations'); to your application’s bootstrap method.

Once the plugin is loaded, run the following command to create a migration file:

bin/cake bake migration CreateArticles title:string body:text category_id:integer created modified

A migration file will be generated in the /config/Migrations folder with the following:

<?php

use Migrations\AbstractMigration;

class CreateArticles extends AbstractMigration
{
    public function change()
    {
        $table = $this->table('articles');
        $table->addColumn('title', 'string', [
            'default' => null,
            'limit' => 255,
            'null' => false,
        ]);
        $table->addColumn('body', 'text', [
            'default' => null,
            'null' => false,
        ]);
        $table->addColumn('category_id', 'integer', [
            'default' => null,
            'limit' => 11,
            'null' => false,
        ]);
        $table->addColumn('created', 'datetime', [
            'default' => null,
            'null' => false,
        ]);
        $table->addColumn('modified', 'datetime', [
            'default' => null,
            'null' => false,
        ]);
        $table->create();
    }
}

Run another command to create a categories table. If you need to specify a field length, you can do it within brackets in the field type, ie:

bin/cake bake migration CreateCategories parent_id:integer lft:integer[10] rght:integer[10] name:string[100] description:string created modified

This will generate the following file in config/Migrations:

<?php

use Migrations\AbstractMigration;

class CreateCategories extends AbstractMigration
{
    public function change()
    {
        $table = $this->table('categories');
        $table->addColumn('parent_id', 'integer', [
            'default' => null,
            'limit' => 11,
            'null' => false,
        ]);
        $table->addColumn('lft', 'integer', [
            'default' => null,
            'limit' => 10,
            'null' => false,
        ]);
        $table->addColumn('rght', 'integer', [
            'default' => null,
            'limit' => 10,
            'null' => false,
        ]);
        $table->addColumn('name', 'string', [
            'default' => null,
            'limit' => 100,
            'null' => false,
        ]);
        $table->addColumn('description', 'string', [
            'default' => null,
            'limit' => 255,
            'null' => false,
        ]);
        $table->addColumn('created', 'datetime', [
            'default' => null,
            'null' => false,
        ]);
        $table->addColumn('modified', 'datetime', [
            'default' => null,
            'null' => false,
        ]);
        $table->create();
    }
}

Now that the migration files are created, you can edit them before creating your tables. We need to change the 'null' => false for the parent_id field with 'null' => true because a top-level category has a null parent_id.

Run the following command to create your tables:

bin/cake migrations migrate

Modifying the Tables

With our tables set up, we can now focus on categorizing our articles.

We suppose you already have the files (Tables, Controllers and Templates of Articles) from part 2. So we’ll just add the references to categories.

We need to associate the Articles and Categories tables together. Open the src/Model/Table/ArticlesTable.php file and add the following:

// src/Model/Table/ArticlesTable.php

namespace App\Model\Table;

use Cake\ORM\Table;

class ArticlesTable extends Table
{
    public function initialize(array $config)
    {
        $this->addBehavior('Timestamp');
        // Just add the belongsTo relation with CategoriesTable
        $this->belongsTo('Categories', [
            'foreignKey' => 'category_id',
        ]);
    }
}

Generate Skeleton Code for Categories

Create all files by launching bake commands:

bin/cake bake model Categories
bin/cake bake controller Categories
bin/cake bake template Categories

Alternatively, you can bake all with just one line:

bin/cake bake all Categories

The bake tool has created all your files in a snap. You can give them a quick read if you want re-familiarize yourself with how CakePHP works.

Note

If you are on Windows remember to use \ instead of /.

You’ll need to edit the following in src/Template/Categories/add.ctp and src/Template/Categories/edit.ctp:

echo $this->Form->control('parent_id', [
    'options' => $parentCategories,
    'empty' => 'No parent category'
]);

Attach TreeBehavior to CategoriesTable

The TreeBehavior helps you manage hierarchical Tree structures in database table. It uses the MPTT logic to manage the data. MPTT tree structures are optimized for reads, which often makes them a good fit for read heavy applications like blogs.

If you open the src/Model/Table/CategoriesTable.php file, you’ll see that the TreeBehavior has been attached to your CategoriesTable in the initialize() method. Bake adds this behavior to any Tables that contain lft and rght columns:

$this->addBehavior('Tree');

With the TreeBehavior attached you’ll be able to access some features like reordering the categories. We’ll see that in a moment.

But for now, you have to remove the following controls in your Categories add and edit template files:

echo $this->Form->control('lft');
echo $this->Form->control('rght');

In addition you should disable or remove the requirePresence from the validator for both the lft and rght columns in your CategoriesTable model:

public function validationDefault(Validator $validator)
{
    $validator
        ->add('id', 'valid', ['rule' => 'numeric'])
        ->allowEmptyString('id', 'create');

    $validator
        ->add('lft', 'valid', ['rule' => 'numeric'])
    //    ->requirePresence('lft', 'create')
        ->notEmpty('lft');

    $validator
        ->add('rght', 'valid', ['rule' => 'numeric'])
    //    ->requirePresence('rght', 'create')
        ->notEmpty('rght');
}

These fields are automatically managed by the TreeBehavior when a category is saved.

Using your web browser, add some new categories using the /yoursite/categories/add controller action.

Reordering Categories with TreeBehavior

In your categories index template file, you can list the categories and re-order them.

Let’s modify the index method in your CategoriesController.php and add moveUp() and moveDown() methods to be able to reorder the categories in the tree:

class CategoriesController extends AppController
{
    public function index()
    {
        $categories = $this->Categories->find()
            ->order(['lft' => 'ASC']);
        $this->set(compact('categories'));
        $this->set('_serialize', ['categories']);
    }

    public function moveUp($id = null)
    {
        $this->request->allowMethod(['post', 'put']);
        $category = $this->Categories->get($id);
        if ($this->Categories->moveUp($category)) {
            $this->Flash->success('The category has been moved Up.');
        } else {
            $this->Flash->error('The category could not be moved up. Please, try again.');
        }
        return $this->redirect($this->referer(['action' => 'index']));
    }

    public function moveDown($id = null)
    {
        $this->request->allowMethod(['post', 'put']);
        $category = $this->Categories->get($id);
        if ($this->Categories->moveDown($category)) {
            $this->Flash->success('The category has been moved down.');
        } else {
            $this->Flash->error('The category could not be moved down. Please, try again.');
        }
        return $this->redirect($this->referer(['action' => 'index']));
    }
}

In src/Template/Categories/index.ctp replace the existing content with:

<div class="actions large-2 medium-3 columns">
    <h3><?= __('Actions') ?></h3>
    <ul class="side-nav">
        <li><?= $this->Html->link(__('New Category'), ['action' => 'add']) ?></li>
    </ul>
</div>
<div class="categories index large-10 medium-9 columns">
    <table cellpadding="0" cellspacing="0">
    <thead>
        <tr>
            <th>Id</th>
            <th>Parent Id</th>
            <th>Lft</th>
            <th>Rght</th>
            <th>Name</th>
            <th>Description</th>
            <th>Created</th>
            <th class="actions"><?= __('Actions') ?></th>
        </tr>
    </thead>
    <tbody>
    <?php foreach ($categories as $category): ?>
        <tr>
            <td><?= $category->id ?></td>
            <td><?= $category->parent_id ?></td>
            <td><?= $category->lft ?></td>
            <td><?= $category->rght ?></td>
            <td><?= h($category->name) ?></td>
            <td><?= h($category->description) ?></td>
            <td><?= h($category->created) ?></td>
            <td class="actions">
                <?= $this->Html->link(__('View'), ['action' => 'view', $category->id]) ?>
                <?= $this->Html->link(__('Edit'), ['action' => 'edit', $category->id]) ?>
                <?= $this->Form->postLink(__('Delete'), ['action' => 'delete', $category->id], ['confirm' => __('Are you sure you want to delete # {0}?', $category->id)]) ?>
                <?= $this->Form->postLink(__('Move down'), ['action' => 'moveDown', $category->id], ['confirm' => __('Are you sure you want to move down # {0}?', $category->id)]) ?>
                <?= $this->Form->postLink(__('Move up'), ['action' => 'moveUp', $category->id], ['confirm' => __('Are you sure you want to move up # {0}?', $category->id)]) ?>
            </td>
        </tr>
    <?php endforeach; ?>
    </tbody>
    </table>
</div>

Modifying the ArticlesController

In our ArticlesController, we’ll get the list of all the categories. This will allow us to choose a category for an Article when creating or editing it:

// src/Controller/ArticlesController.php

namespace App\Controller;

// Prior to 3.6 use Cake\Network\Exception\NotFoundException
use Cake\Http\Exception\NotFoundException;

class ArticlesController extends AppController
{
    // ...

    public function add()
    {
        $article = $this->Articles->newEntity();
        if ($this->request->is('post')) {
            // Prior to 3.4.0 $this->request->data() was used.
            $article = $this->Articles->patchEntity($article, $this->request->getData());
            if ($this->Articles->save($article)) {
                $this->Flash->success(__('Your article has been saved.'));
                return $this->redirect(['action' => 'index']);
            }
            $this->Flash->error(__('Unable to add your article.'));
        }
        $this->set('article', $article);

        // Just added the categories list to be able to choose
        // one category for an article
        $categories = $this->Articles->Categories->find('treeList');
        $this->set(compact('categories'));
    }
}

Modifying the Articles Templates

The article add file should look something like this:

<!-- File: src/Template/Articles/add.ctp -->

<h1>Add Article</h1>
<?php
echo $this->Form->create($article);
// just added the categories control
echo $this->Form->control('category_id');
echo $this->Form->control('title');
echo $this->Form->control('body', ['rows' => '3']);
echo $this->Form->button(__('Save Article'));
echo $this->Form->end();

When you go to the address /yoursite/categories/add you should see a list of categories to choose.