[英]How to correctly use relationships with() in Laravel?
我只是想澄清使用表中的關系。 現在,我想從employees
表中的designation_id
中獲取designation names
的記錄。
<?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'); } }
這是我的編號 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'); } }
這是我的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); } }
我檢查了我的 api url, http://localhost:8000/api/employees 並得到了這個錯誤:
SQLSTATE[HY093]: Invalid parameter number (SQL: select * from
.
where
designations .id in (52))
你的關系參數是錯誤的。 它是
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');
}
如果您渴望加載超過 1 個關系,請使用數組表示法。
此外, $employees
將是Collection
的一個實例,因此您不能將它用作array_reverse
的參數。
您可以使用集合方法來獲得相同的結果,或者使用$employees->all()
來獲取底層數組。
<?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());
}
}
這是假設您的表具有如下結構:
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');
...
});
由於您使用的是increments
而不是id()
,因此代碼必須略有不同。
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');
...
});
我會建議你安裝 phpstorm,它會給你提示 function 參數,你不會再有這種問題了。
正確的格式是:
return $this->hasMany('App\Comment', 'foreign_key', 'local_key');
在您的指定 model 中:
public function DesignationNames() { return $this->hasMany(\App\Models\Employees::class, 'designation_id', 'id'); }
當您在 controller 中檢索它們時,您需要使用 with() 方法:
指定::with('DesignationNames')->get();
然后要訪問相關員工集合中的屬性,您需要:
$designation->DesignationNames->DesignationProperty
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