How to correctly use relationships with() in Laravel? - laravel

Question

I just wanted to clarify using the relationship in tables. Right now, I wanted to fetch records of designation names from designation_id in employees table.
<?php
namespace App\Models;
use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;
use App\Models\{
Designations,
Positions
};
class Employees extends Model
{
use HasFactory;
protected $table = 'employees';
protected $primaryKey = 'id';
public $timestamps = true;
protected $casts = [
'designation_id' => 'array',
'position_id' => 'array',
'basic_pay' => 'decimal:2',
];
protected $dates = ['created_at', 'updated_at'];
protected $fillable = [
'first_name',
'last_name',
'designation_id',
'position_id',
'basic_pay',
];
public function designations()
{
return $this->hasMany(Designations::class, 'id', 'designation_id');
}
public function positions()
{
return $this->hasMany(Positions::class, 'id', 'position_id');
}
}
Here's my designation model:
<?php
namespace App\Models;
use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;
use App\Models\Employees;
class Designations extends Model
{
use HasFactory;
protected $table = 'designations';
protected $primaryKey = 'id';
public $timestamps = true;
protected $dates = ['created_at', 'updated_at'];
protected $fillable = [
'name',
'description'
];
public function employees()
{
return $this->belongsTo(Employees::class, 'designation_id');
}
}
Here's my EmployeeController.php:
<?php
namespace App\Http\Controllers;
use Illuminate\Http\Request;
use App\Models\{
Employees,
Designations
};
class EmployeesController extends Controller
{
public function index()
{
$employees = Employees::with('designations', 'positions')->get();
return array_reverse($employees);
}
}
I checked my api url, http://localhost:8000/api/employees and got this error:
SQLSTATE[HY093]: Invalid parameter number (SQL: select * from designationswheredesignations.id in (52))

Answer 1

I would recommend you to install phpstorm, it gives you hints of function parameters and you won't have this kind of issues anymore.
correct format is:
return $this->hasMany('App\Comment', 'foreign_key', 'local_key');
in your designations model:
public function DesignationNames()
{
return $this->hasMany(\App\Models\Employees::class, 'designation_id', 'id');
}
When you retrieve them in your controller you need to use the with() method as:
Designations::with('DesignationNames')->get();
And then to access properties in the related employee collection you would need to:
$designation->DesignationNames->DesignationProperty

Answer 2

Your relationships parameters are wrong. It's
hasMany(class, foreignKey, relatedPrimaryKey)
# Employee
public function designations()
{
return $this->hasMany(Designations::class, 'employee_id', 'id');
}
public function positions()
{
return $this->hasMany(Positions::class, 'employee_id', 'id');
}
If you're eager loading more than 1 relationship, use array notation.
Also, $employees will be an instance of a Collection, so you can't use it as an argument to array_reverse.
You can either use collection methods to achieve the same result, or use $employees->all() to get the underlying array.
<?php
namespace App\Http\Controllers;
use Illuminate\Http\Request;
use App\Models\Employees;
class EmployeesController extends Controller
{
public function index()
{
$employees = Employees::with(['designations', 'positions'])->get();
return $employees->reverse()->values()->all();
// OR
return array_reverse($employees->all());
}
}
This is assuming your tables have a structure like this:
Schema::create('employees', function (Blueprint $table) {
$table->id();
...
});
Schema::create('designations', function (Blueprint $table) {
$table->id();
$table->foreignId('employee_id')->constained('employees');
...
});
Schema::create('positions', function (Blueprint $table){
$table->id();
$table->foreignId('employee_id')->constained('employees');
...
});
Since you're using increments instead of id(), the code has to be a little different.
Schema::create('employees', function (Blueprint $table) {
$table->increments('id')->unique();
...
});
Schema::create('designations', function (Blueprint $table) {
$table->increments('id')->unique();
$table->unsignedInteger('employee_id');
$table->foreign('employee_id')->references('id')->on('employees');
...
});
Schema::create('positions', function (Blueprint $table){
$table->increments('id')->unique();
$table->unsignedInteger('employee_id');
$table->foreign('employee_id')->references('id')->on('employees');
...
});