Setting Defaults in Laravel Eloquent Models: 5 Powerful Techniques

Introduction

When working with Laravel Eloquent Models, setting default values for various attributes can be an essential requirement. In this post, we'll explore five different ways to set default values in a Laravel 10 Eloquent Model, each with unique characteristics and use cases.

1. Use of the $attributes Array
   The simplest and most straightforward way to set default values for your Eloquent model's attributes. Only accepts scalar defaults and applies only to the initial object.
2. Using Accessors
   Allows considering other attributes of the Model and applies dynamically throughout the lifecycle of the Model. It enables manipulation of attribute values dynamically.
3. Using Database Defaults
   Best for attributes that have little to do with data retrieved by the application, like timestamps and IDs. It may also be used as a last resort in some cases.
4. Use of Protected static function boot()
   Allows using a method or service to set a default value at initialization. Useful when scalar defaults are not sufficient.
5. Using CastsAttributes
   Casting allows converting attribute values and setting defaults through custom casting. Requires that the attribute already be set when retrieving and may require setting an initial value (typically null) in the $attributes array.

Example: Product Model

Let's create a Product model that utilizes all the mentioned techniques on different fields:

use Illuminate\Database\Eloquent\CastsAttributes;

class Product extends Model
{
    protected $attributes = [
        'status' => 'active',
        'metadata' => null, // Initial value for custom cast
    ];

    protected $casts = [
        'metadata' => MetadataCast::class, // Custom cast for metadata
    ];

    protected static function boot()
    {
        parent::boot();

        static::creating(function ($model) {
            $model->slug = Str::slug($model->name);
        });
    }

    public function getPriceAttribute($value)
    {
        // Apply a discount or format the price based on other attributes
        return $value * 0.9; // Example: 10% discount
    }

    public function getStatusAttribute($value)
    {
        return $value ?: 'active';
    }
}

class MetadataCast implements CastsAttributes
{
    public function get($model, $key, $value, $attributes)
    {
        return json_decode($value) ?: ['default_key' => 'default_value'];
    }

    public function set($model, $key, $value, $attributes)
    {
        return json_encode($value);
    }
}

// Migration example for database defaults
Schema::create('products', function (Blueprint $table) {
    $table->id();
    $table->string('name');
    $table->string('slug');
    $table->decimal('price');
    $table->string('status')->default('active');
    $table->timestamps(); // created_at will be set by default
});

In this example, different attributes of a product are handled using different techniques, demonstrating the flexibility and power of Laravel's Eloquent.

Conclusion

Setting default values in Laravel Eloquent Models can be achieved in various ways, each with its own strengths and use cases. From the simplest $attributes array to more complex boot methods and custom casting, Laravel provides a rich set of tools for managing default values. The provided example illustrates how these can be combined in a cohesive manner to create a robust and flexible model.

I hope this has been helpful in understanding the different techniques available. If you have any questions or need further clarification on any of the methods discussed, please feel free to leave a comment below. Additionally, if you have discovered or utilized other ways to set default values in Laravel that were not covered in this post, we encourage you to share them with the community. Your insights and contributions can help others in their development journey.