# Relationships

We provide "basic" support for all relationship types. This gives you the ability to associate models with other models, be it a 1 to 1 relationship, or many to many.

# Associating Relationships

It's best to explicitly define your relationships to make sure they update correctly - which you can do e.g.

public function __construct()
{
    $this->panel->setRelationships([
        'tags' => 'tags',
        'category_id' => 'category',
    ])
}

The structure above represents a mapping between a form input name, and the relationship method name.

If you have an HTML form with an input with the name of category_id e.g. $_POST['category_id'] and you want it to update the category relationship, you would have

[ 'category_id' => 'category' ]

For the UI components for relationships you'll want to either use a Select input or the Transfer input.

# Updating Associated Models

If you have a relationship such as a hasOne connecting entities like meta data to a post or page you can do so via a mixture of dot notation and relationship mapping.

class Page extends Model
{
    public function meta()
    {
        return $this->hasOne(MetaData::class);
    }
}

class MetaData extends Model
{
    protected $fillable = [
        'description',
    ];
    
    public function page()
    {
        return $this->belongsTo(Page::class);
    }
}

You can access the field data via dot notation within your forms e.g. relationshipMethod.attributeName

@include('maelstrom::inputs.text', [
    'name' => 'meta.description',
])

Once your relationship is defined you can map it via setRelationships.

Laravel converts dot notation requests into underscores, this means:

meta.description becomes meta_description.

You can use the meta_ prefix to define a group of related fields e.g. meta_description and meta_keywords e.g.

$this->panel->setRelationships([
    'meta_' => 'meta',
])

Any post data that starts with meta_ will get assigned on the meta relationship e.g.

meta_description will get assigned to $entry->meta->description.

# Eager Loading

When loading your entries, you might want to load all the relationships in one go for performance reasons, if this is the case you can do so by defining the names of the relationships to eager load.

So if you have the following relationships on your model:

class Page extends Model
{
    public function category()
    {
        return $this->belongsTo(Category::class);
    }
    
    public function tags()
    {
        return $this->>belongsToMany(Tag::class);
    }
}

You can eager load them via passing an array with the method name of the relationship

public function __construct()
{
    $this->panel->setEagerLoad(['category', 'tags']);
}