belongsTo on pivot table

[caiokawasaki]

Yesterday I spent a few hours trying to resolve this, I ended up with a solution but I didn't really like it.

I started developing a multi-tenancy application and came across an issue when resolving user relations.

Each user can only belong to one Tenant, when he creates his account he is automatically attached to the Tenant related to the domain. When any user is loaded, Tenant is automatically loaded so that the system can know the user's role, the only issue is that I couldn't bring in just one Tenant, I need to bring them all in and then filter.

These are my models:

class User extends Authenticatable
{
    protected $fillable = [
        'first_name',
        'last_email',
        'password',
    ];

    protected $hidden = [
        'password',
        'remember_token',
    ];

    protected $casts = [
        'email_verified_at' => 'datetime',
        'password' => 'hashed',
    ];

    protected $with = [
        'tenants',
    ];


    public function tenants(): BelongsToMany
    {
        return $this->belongsToMany(Tenant::class, 'tenant_user')
            ->using(TenantUser::class)
            ->withPivot(['role']);
    }
}

class Tenant extends Model
{
    protected $fillable = [
        'name',
        'domain',
    ];


    public function users(): BelongsToMany
    {
        return $this->belongsToMany(User::class, 'tenant_user')
            ->using(TenantUser::class)
            ->withPivot(['role']);
    }
}

My pivot class:

class TenantUser extends Pivot
{
    protected $table = 'tenant_user';

    protected $fillable = [
        'role'
    ];

    protected $hidden = [
        'tenant_id',
        'user_id',
    ];


    public function tenant(): BelongsTo
    {
        return $this->belongsTo(Tenant::class, 'tenant_id');
    }

    public function user(): BelongsTo
    {
        return $this->belongsTo(User::class, 'user_id');
    }
}

My solution was the following:

class User extends Authenticatable
{
    protected $fillable = [
        'first_name',
        'last_email',
        'password',
    ];

    protected $hidden = [
        'password',
        'remember_token',
    ];

    protected $casts = [
        'email_verified_at' => 'datetime',
        'password' => 'hashed',
    ];

    protected $with = [
        'tenants',
    ];

    protected $appends = [
        'role',
    ];
    
    
    public function tenants(): BelongsToMany
    {
        return $this->belongsToMany(Tenant::class, 'tenant_user')
            ->using(TenantUser::class)
            ->withPivot(['role']);
    }


    protected function role(): Attribute
    {
        return new Attribute(
            get: fn() => $this->tenants->first()->pivot->role
        );
    }
}

I would like to do something similar to this:

class User extends Authenticatable
{
    protected $fillable = [
        'first_name',
        'last_email',
        'password',
    ];

    protected $hidden = [
        'password',
        'remember_token',
    ];

    protected $casts = [
        'email_verified_at' => 'datetime',
        'password' => 'hashed',
    ];

    protected $with = [
        'tenant',
    ];

    protected $appends = [
        'role',
    ];


    public function tenant(): BelongsToMany
    {
        return $this->belongsTo(Tenant::class, 'tenant_user') // belongsTo is only accepted when in the same table
            ->using(TenantUser::class)
            ->withPivot(['role']);
    }


    protected function role(): Attribute
    {
        return new Attribute(
            get: fn() => $this->tenant->pivot->role
        );
    }
}

Is this possible?

Edit

I achieved something similar to what I want with the following relationship:

class User extends Authenticatable
{
	public function tenant()
    {
        return $this->hasOneThrough(
            Tenant::class,
            TenantUser::class,
            'tenant_id',
            'id',
            'id',
            'user_id'
        );
    }
}

However, this way I cannot access the other columns of the pivot table.

[haleyngonadi]

Since a user has just one tenant, should the users table have a tenent_id?

[caiokawasaki]

I want to use a separate table because user will have configurations related to the tenant, I don't want to keep it on the users table

[macropay-solutions]

@caiokawasaki You could create a new relation class that extends BelongsToMany and in it you should overwrite

 /**
 * Get the results of the relationship.
 *
 * @return mixed
 */
public function getResults()
{
    return ! is_null($this->parent->{$this->parentKey})
            ? $this->get()
            : $this->related->newCollection();
}

so you get first result. Maybe

return parent::getResults()->first();

Also unique on user_id from pivot.

in belongs to:

/**
 * Get the results of the relationship.
 *
 * @return mixed
 */
public function getResults()
{
    if (is_null($this->child->{$this->foreignKey})) {
        return $this->getDefaultFor($this->parent);
    }

    return $this->query->first() ?: $this->getDefaultFor($this->parent);
}