Using Laravel Eloquent's hasMany to develop Infinitus classification

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In online shopping malls, we can often see multi-level classifications, sub-categories, and even Infinitus classifications. This article will show you how to elegantly implement it with Laravel Eloquent.

We will create a micro project to display the classification of children's stores, with a total of 5 levels, as follows:

Database migration

Simple data table structure:

Schema::create('categories', function (Blueprint $table) {
    $table->bigIncrements('id');
    $table->string('name');
    $table->unsignedBigInteger('category_id')->nullable();
    $table->foreign('category_id')->references('id')->on('categories');
    $table->timestamps();
});

There is only one name field, related to itself. Therefore, most parent categories category_id = NULL, and each subcategory has a parent_id

The data table data is as follows:

##Eloquent model And the relationship

First, create a simple hasMany() method in app/Category.php. The category may have its own self-categorization:

class Category extends Model
{
    public function categories()
    {
        return $this->hasMany(Category::class);
    }
}

The show starts with the best part of this article" plan". Did you know that you can describe a recursive relationship like this? As follows:

public function childrenCategories()
{
    return $this->hasMany(Category::class)->with('categories');
}

Therefore, if you call Category::with(‘categories’), you will get the lower-level “subcategories”, but Category::with(‘childrenCategories’) will help you achieve infinity.

Routes and Controller Methods

Now, let us try to display all categories and subcategories as shown in the above example.

In routes/web.php, we add the following:

Route::get('categories', 'CategoryController@index');

app/Http/CategoryController.php as shown below:

public function index()
{
    $categories = Category::whereNull('category_id')
        ->with('childrenCategories')
        ->get();
    return view('categories', compact('categories'));
}

We only load the parent category and add Subcategories as relationships. Simple right?

Views and recursive subviews

Finally, render to the page. In the resources/views/categories.blade.php file:

<ul>
    @foreach ($categories as $category)
        <li>{{ $category->name }}</li>
        <ul>
        @foreach ($category->childrenCategories as $childCategory)
            @include(&#39;child_category&#39;, [&#39;child_category&#39; => $childCategory])
        @endforeach
        </ul>
    @endforeach
</ul>

We first traverse the top-level parent category, then traverse out the subcategories of the parent class, and then use @include to load the subcategories of the subcategory.. ....

The best part is that resources/views/admin/child_category.blade.php will load itself recursively. Look at the code:

<li>{{ $child_category->name }}</li>
@if ($child_category->categories)
    <ul>
        @foreach ($child_category->categories as $childCategory)
            @include(&#39;child_category&#39;, [&#39;child_category&#39; => $childCategory])
        @endforeach
    </ul>
@endif

Inside child_category.blade.php, we include @include(‘child_category’), so the template will recursively load subcategories as long as there are categories in the current subcategory.

That's it! We have unlimited levels of subcategories - whether in databases or relationships or views

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