如何在Laravel中获取三级关联模型数据

要在现有接口中获取第三级表EducationalAward的award字段，只需利用Eloquent的嵌套关联预加载功能，修改控制器方法即可：

public function getEducationalBackground($id) 
{
    $educationalBackground = EducationalBackground::with(['user', 'educationalAwards'])
        ->where('user_id', $id)
        ->get();

    return response()->json($educationalBackground, 200);
}

可选：仅返回指定字段 #

如果只需要EducationalAward中的award字段（而非所有字段），可以在预加载时指定字段列表（注意必须包含关联外键educational_background_id，否则无法正确关联数据）：

public function getEducationalBackground($id) 
{
    $educationalBackground = EducationalBackground::with([
            'user',
            'educationalAwards:id,educational_background_id,award'
        ])
        ->where('user_id', $id)
        ->get();

    return response()->json($educationalBackground, 200);
}

User模型 #

class User extends Authenticatable
{
    use HasFactory, Notifiable, HasApiTokens, HasRoles;

    const MALE = 'male';
    const FEMALE = 'female';

    protected $guard_name = 'sanctum';


    public function educationalBackgrounds()
    {
        return $this->hasMany("App\Models\Users\EducationalBackground", "user_id");
    }

    public function seminars()
    {
        return $this->hasMany("App\Models\Users\Seminar", "user_id");
    }
}

EducationalBackground模型 #

class EducationalBackground extends Model
{
    use HasFactory;

    protected $table = 'users.educational_backgrounds';
    protected $fillable = [
        'user_id',
        'studies_type',
        'year',
        'course',
    ];

    public function user()
    {
        return $this->belongsTo('App\Models\User', 'user_id');
    }

    public function educationalAwards()
    {
        return $this->hasMany("App\Models\Users\EducationalAward", "educational_background_id");
    }
}

EducationalAward模型 #

class EducationalAward extends Model
{
    use HasFactory;

    protected $table = 'users.educational_awards';
    protected $fillable = [
        'educational_background_id',
        'award',
        'photo',
    ];

    public function educationalBackground()
    {
        return $this->belongsTo('App\Models\Users\EducationalBackground', 'educational_background_id');
    }
}

API路由 #

Route::get('/educational-background/{id}', [UserProfileController::class, 'getEducationalBackground']);

内容的提问来源于stack exchange，提问作者Kael