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Laravel – Custom Intermediate Table Models – eager loading

Here is my current setup:

<?php

namespace AppModels;

use Exception;
use IlluminateDatabaseEloquentModel;
use IlluminateDatabaseEloquentRelationsBelongsTo;
use IlluminateDatabaseEloquentRelationsBelongsToMany;

class Employee extends Model
{
    protected $table = 'employees';

    protected $fillable = [
        'first_name', 'last_name', 'gender',
        'birthdate', 'nationality_id', 'company_id',
    ];

    public function positions(): BelongsToMany
    {
        return $this->belongsToMany(Position::class)
            ->using(EmployeePosition::class);
    }
}


<?php

namespace AppModels;

use IlluminateDatabaseEloquentModel;
use IlluminateDatabaseEloquentRelationsBelongsToMany;

class Position extends Model
{
    protected $table = 'positions';

    protected $fillable = [
        'name',
    ];

    public function employees(): BelongsToMany
    {
        return $this->belongsToMany(Employee::class)
            ->using(EmployeePosition::class);
    }
}

These connect to each other through a Pivot table, which is configured as "Custom Intermediate Table Models" according to docs.

I’ve set the following cols:
| id | employee_id | position_id |

<?php

namespace AppModels;

use IlluminateDatabaseEloquentRelationsHasMany;
use IlluminateDatabaseEloquentRelationsHasManyThrough;
use IlluminateDatabaseEloquentRelationsPivot;

class EmployeePosition extends Pivot
{
    /**
     * Indicates if the IDs are auto-incrementing.
     *
     * @var bool
     */
    public    $incrementing = true;
    protected $table        = 'employee_position';
}

Having $employee, up to here it works fine:
$employee->load('positions')

Next, I also created a employee_position_technologies table:

<?php

namespace AppModels;

use IlluminateDatabaseEloquentModel;

class EmployeePositionTechnology extends Model
{
    protected $table = 'employee_position_technologies';

    protected $fillable = [
        'employee_position_id',
        'technology_id',
    ];
}

I want to assign many "technologies" to the "EmployeePosition".
I’ve also achieved that.

Now, what I am trying to achieve is load technologies to the Employee positions accordingly:
$employee->load('positions.technologies')

For this, I’ve modified the EmployeePosition class, adding the technologies() method like so:

    public function technologies()
    {
        return $this->hasManyThrough(
            Technology::class,
            EmployeePositionTechnology::class,
            'employee_position_id',
            'id',
            'position_id',
            'technology_id'
        );
    }

this does not work, as the technologies() method seems to be searched from the
Position Model.

I’ve found that to access the "Intermediate Table Models" we have to use something like:
$employee->position->pivot->technologies

so I tried:
$employee->load('positions.pivot.technologies');

which also does not seem to work, with error
Call to undefined relationship [pivot] on model [AppModelsPosition].

next, although I do not like it, I tried:

$employee->load('positions');

$employee->positions->each(function ($position) {
    $position->pivot->load('technologies');
});

This seems to work, and I can access the method, but the resulting technologies relation of the position is empty.

I tried to dump the query, and it seems correct:

select * from "technologies" 
inner join "employee_position_technologies" 
on "employee_position_technologies"."technology_id" = "technologies"."id" 
where "employee_position_technologies"."employee_position_id" = ?

what am I missing?

Tags:

2

Answers


  1. 0

    Have you tried using the with() method in place of load() method to eager load the relationship you are trying to load? You can achieve this using the with keyword as shown below where the relationship is passed as arguement to the with method

    $employee->positions()->with('technologies')->get();

    This will return all positions found for the employee along with the related technologies for each position if there are any. You can read more on using with method for eager loading from the Laravel official website

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  2. 0

    What You’re Missing:

    The root issue lies in how Laravel handles relationships defined on custom pivot models. Eloquent doesn’t automatically treat the pivot model (EmployeePosition) as a fully-fledged model with its own relationships when using eager loading ($employee->load('positions.pivot.technologies')). Here’s what you’re missing and why your current approaches fail:

    Why $employee->load('positions.pivot.technologies') Fails:

    1. Pivot Relationships Aren’t Auto-Resolved:
      Laravel doesn’t automatically recognize relationships (technologies) defined on a pivot model when eager-loading a BelongsToMany relationship. It treats the pivot data as raw attributes attached to the parent model (Position) and doesn’t dive into the pivot relationships.

    2. Accessing pivot with load() is Unsupported:
      When you try $employee->load('positions.pivot.technologies'), Laravel tries to find a pivot relationship on the Position model, which doesn’t exist. The pivot is not a direct relationship but an instance of your EmployeePosition model.

    Why $position->pivot->load('technologies') Returns Empty:

    The query itself might be correct, but you’re likely missing one of these:

    • employee_position_id in Pivot Table: Ensure the employee_position_id column exists in the employee_position_technologies table and contains valid references.
    • Pivot Data Is Not Loaded Automatically:
      When looping through $employee->positions, Laravel doesn’t automatically hydrate the pivot model with its relationships unless explicitly loaded.

    Complete Working Solution

    1. Define the Relationship on the Pivot Model

    Make sure your EmployeePosition model has the correct technologies() relationship:

    <?php

namespace AppModels;

use IlluminateDatabaseEloquentRelationsHasManyThrough;
use IlluminateDatabaseEloquentRelationsPivot;

class EmployeePosition extends Pivot
{
    protected $table = 'employee_position';

    public $incrementing = true;

    protected $fillable = [
        'employee_id', 'position_id',
    ];

    public function technologies(): HasManyThrough
    {
        return $this->hasManyThrough(
            Technology::class,
            EmployeePositionTechnology::class,
            'employee_position_id', // Foreign key on EmployeePositionTechnology
            'id',                   // Foreign key on Technology
            'id',                   // Local key on EmployeePosition
            'technology_id'         // Local key on EmployeePositionTechnology
        );
    }
}

    2. Update the Employee Model

    In the positions() method, ensure that the pivot data (id) is available using withPivot():

    public function positions(): BelongsToMany
{
    return $this->belongsToMany(Position::class)
        ->using(EmployeePosition::class)
        ->withPivot(['id']) // Ensure pivot ID is included
        ->withTimestamps();
}

    3. Eager Load Technologies on the Pivot

    Since Laravel doesn’t support eager loading directly through pivot relationships, manually load the technologies relationship like this:

    $employee = Employee::with('positions')->find($employeeId);

$employee->positions->each(function ($position) {
    if ($position->pivot instanceof EmployeePosition) {
        $position->pivot->load('technologies');
    }
});

    4. Access the Data

    After loading, you can access the technologies like this:

    foreach ($employee->positions as $position) {
    $technologies = $position->pivot->technologies;

    foreach ($technologies as $technology) {
        echo $technology->name; // Or process as needed
    }
}

    Alternative: Custom Scope for Cleaner Code

    If this pattern is frequent, define a custom scope to streamline the process.

    public function scopeWithTechnologies($query)
{
    $query->with(['positions' => function ($q) {
        $q->with(['pivot.technologies']);
    }]);
}

    Use it like this:

    $employee = Employee::withTechnologies()->find($employeeId);

    Key Insights:

    1. Pivot Models Need Manual Loading: Laravel doesn’t automatically load relationships on pivot models. You must manually call load() on the pivot.
    2. Ensure Proper Foreign Key Mapping: Double-check the keys in EmployeePositionTechnology and your pivot table setup.
    3. Eager Load Smartly: Use loops or scopes to manage eager loading cleanly.

    This ensures your technologies are properly loaded, adhering to Laravel’s best practices.

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