too long

Right now I try this query with eloquent:

'MentorId'  => $employee->intern(true)->mentor(true)->MentorId,

And in my employee and intern model I've got this:

Intern

  /**
     * @return mixed
     */
    public function intern($withTrashed = false)
    {
        if($withTrashed == true)
        {
            return $this->belongsTo(internModel::class, 'InternId')->withTrashed();
        }

        return $this->belongsTo(internModel::class,'InternId');
    }

Mentor

 /**
     * @return mixed
     */
    public function mentor($withTrashed = false)
    {
        if($withTrashed == true)
        {
            return $this->belongsTo(mentorModel::class, 'MentorId')->withTrashed();
        }

        return $this->belongsTo(mentorModel::class,'MentorId');
    }

But it crashes:

BadMethodCallException in Builder.php line 2148:
Call to undefined method Illuminate\Database\Query\Builder::mentor()

How could I fix this?

--EDIT--

Employee

<?php

namespace App\src\employee;

use Illuminate\Foundation\Auth\User as Authenticatable;
use App\src\department\Department as departmentModel;
use App\src\employee\Employee as employeeModel;
use Illuminate\Database\Eloquent\SoftDeletes;
use App\src\intern\Intern as internModel;
use App\src\mentor\Mentor as mentorModel;
use App\src\employee\Role as roleModel;

class Employee extends Authenticatable
{
    use SoftDeletes;
    use EmployeeServiceTrait;

    /**
     * table name
     */
    protected $table = 'employee';

    /**
     * Mass assignment fields
     */
    protected $fillable = ['RoleId', 'DepartmentId', 'InternId', 'FirstName', 'LastName', 'Bio','api_token', 'email', 'LinkedIn', 'password', 'Address', 'Zip', 'City', 'ProfilePicture', 'BirthDate', 'StartDate', 'EndDate', 'Suspended','LinkedIn'];

    /**
     * Primarykey
     */
    protected $primaryKey = 'EmployeeId';

    /**
     * Deleted_at
     */
    protected $dates = ['deleted_at'];

    /**
     * @return mixed
     */
    public function role()
    {
        return $this->belongsTo(roleModel::class,'RoleId');
    }

    /**
     * @return mixed
     */
    public function intern($withTrashed = false)
    {
        if($withTrashed == true)
        {
            return $this->belongsTo(internModel::class, 'InternId')->withTrashed();
        }

        return $this->belongsTo(internModel::class,'InternId');
    }

    /**
     * @return mixed
     */
    public function department()
    {
        return $this->belongsTo(departmentModel::class,'DepartmentId');
    }

    /**
     * @return mixed
     */
    public function mentor()
    {
        return $this->belongsTo(mentorModel::class,'MentorId');
    }

    /**
     * @return mixed
     */
    public function employees()
    {
        return $this->hasManyThrough(employeeModel::class,departmentModel::class,'CompanyId','DepartmentId');
    }

    /**
     * @param $role
     * @return bool
     */
    public function hasRole($role)
    {
        if(strtolower($this->role->RoleName) == strtolower($role))
        {
            return true;
        }
        return false;
    }
}

The problem you have is that any Eloquent relationship object is actually an instance of Relation. This means when you create relationships you actually return a collection (instance of Builder); Hense your error:

BadMethodCallException in Builder.php line 2148: Call to undefined method Illuminate\Database\Query\Builder::mentor()

The simple solution, without any modification to your code would be something like:

'MentorId'  => $employee->intern(true)->first()->mentor(true)->first()->MentorId;

However, you could use overloading like the following:

'MentorId'  => $employee->intern->mentor->MentorId;

Although this will NOT include your withTrashed. You can however tweak your relationship to something like:

public function intern($withTrashed = false)
{
    $relation = $this->belongsTo(internModel::class, 'InternId');

    if($withTrashed == true)
    {
        return $relation->withTrashed()->first();
    }

    return $relation->first();
}

But I wouldn't advise this because later on if you try using things like WhereHas you will get errors. That said, another way would be to do something along the following lines:

public function intern()
{
    return $this->belongsTo(internModel::class, 'InternId');
}

Then get trashed like:

'MentorId' => $employee->intern()->withTrashed()->first()->mentor()->withTrashed()->first()->MentorId;

Try as below as per laravel guide. Keep in mind that parent model must have hasOne/hasMany method and child model must have belongsTo method.

Intern

/**
 * @return mixed
 */
public function intern($withTrashed = false)
{
    if($withTrashed == true)
    {
        return $this->hasOne('App\Intern', 'InternId')->withTrashed();
    }

    return $this->hasOne('App\Intern','InternId');
}  

Employee

/**
 * @return mixed
 */
public function intern($withTrashed = false)
{
    if($withTrashed == true)
    {
        return $this->belongsTo('App\Intern', 'InternId')->withTrashed();
    }

    return $this->belongsTo('App\Intern','InternId');
}

Note: Same for all other models.