Eloquent 关系图例（译）

class Owner
{
    public function car()
    {
       return $this->hasOne(Car::class);
    }
}
class Car
{
    public function owner()
    {
        return $this->belongsTo(Owner::class);
    }
}Copy

Schema::create('owners', function (Blueprint $table) {
    $table->increments('id');
    $table->string('name');
});
Schema::create('cars', function (Blueprint $table) {
    $table->increments('id');
    $table->string('name');
    $table->integer('owner_id')->unsigned()->index()->nullable();
    $table->foreign('owner_id')->references('id')->on('owners');
});Copy

// 更新car和owner之间的关系
$owner->car()->save($car);
$car->owner()->associate($owner)->save();

注：两个的效果其实是一样的，都是更新Car列表中的owner_id。这样一来，我们就无需使用以下这样的更新方式。
Car::where('id',$car->id)->update(['owner_id' => $owner->id]);Copy

//获取当前Owner拥有的car
$owner->car;
//获取当前car的Owner
$car->owner;Copy

class Owner
{
    public function cars()
    {
       return $this->hasMany(Car::class);
    }
}
class Car
{
    public function owner()
    {
        return $this->belongsTo(Owner::class);
    }
}Copy

Schema::create('owners', function (Blueprint $table) {
    $table->increments('id');
    $table->string('name');
});
Schema::create('cars', function (Blueprint $table) {
    $table->increments('id');
    $table->string('name');
    $table->integer('owner_id')->unsigned()->index()->nullable();
    $table->foreign('owner_id')->references('id')->on('owners');
});Copy

// 更新car和owner之间的关系
这边和上面就有些不太一样了
$owner->cars()->saveMany([
   $car1, 
   $car2,
]);
一次性更新多台车的owner_id
$owner->cars()->save($car);
获取和上文一样，更新单个model

$car->owner()->associate($owner)->save();Copy

//获取当前Owner拥有的car
$owner->cars;
//获取当前car的Owner
$car->owner;Copy

class Man
{
    public function cars()
    {
        return $this->morphMany(Car::class, 'buyer');
    }
}
class Woman
{
    public function cars()
    {
        return $this->morphMany(Car::class, 'buyer');
    }
}
class Car
{
    public function buyer()
    {
        return $this->morphTo();
    }
}
从这边来说，我们将hasMany变成了morphMany，同时增加了一个buyer关系。而Car中的belongTo也变成了morphToCopy

Schema::create('men', function (Blueprint $table) {
    $table->increments('id');
    $table->string('name');
});
Schema::create('women', function (Blueprint $table) {
    $table->increments('id');
    $table->string('name');
});
Schema::create('cars', function (Blueprint $table) {
    $table->increments('id');
    $table->string('name');

    $table->morphs(‘buyer’);
    //以下两句可以被上面这句所替代
    //$table->integer('buyer_id')->unsigned()->index()->nullable();
    //$table->string('buyer_type')->nullable();   
});Copy

//修改Car表中的数据
/*
$man:   id=1
$car1: id =1, buyer_id=null, buyer_type= null
经过操作后
$car1: id = 1, buyer_id=1, buyer_type= man
*/
$man->cars()->saveMany([
   $car1, 
   $car2,
]);
$woman->cars()->saveMany([
   $car1, 
   $car2,
]);

// 以下为单Model操作
$man->cars()->save($car);
$woman->cars()->save($car);

// 同上，变动的是buyer_id和buyer_type
$car1->buyer()->associate($man)->save();
$car2->buyer()->associate($woman)->save();Copy

//获取所属的cars
$men->cars
$women->cars
// 获取Car的buyer数据，Man或者Woman
$car->buyerCopy

class Driver
{
    public function cars()
    {
       return $this->belongsToMany(Car::class);
    }
}
class Car
{
    public function drivers()
    {
        return $this->belongsToMany(Driver::class);
    }
}Copy

Schema::create('drivers', function (Blueprint $table) {
    $table->increments('id');
    $table->string('name');
});
Schema::create('cars', function (Blueprint $table) {
    $table->increments('id');
    $table->string('name');
});
Schema::create('car_driver', function (Blueprint $table) {
    $table->increments('id');

    $table->integer('car_id')->unsigned()->index();
    $table->foreign('car_id')->references('id')->on('cars')->onDelete('cascade');

    $table->integer('driver_id')->unsigned()->index();
    $table->foreign('driver_id')->references('id')->on('drivers')->onDelete('cascade');
});
Copy

// 多数据存储,更新关联表的car_id
$driver->cars()->attach([
   $car1->id,
   $car2->id,
]);

// 反向操作，更新关联表的driver_id
$car->drivers()->attach([
   $driver1->id,
   $driver2->id,
]);Copy

// 获取相关联的cars
$driver->cars
// 获取相关联的drivers
$car->driversCopy

class Valet
{
    public function cars()
    {
        return $this->morphToMany(Car::class, 'driver');
    }
}
class Owner
{
    public function cars()
    {
        return $this->morphToMany(Car::class, 'driver');
    }
}
class Car
{
    public function valets()
    {
        return $this->morphedByMany(Valet::class, 'driver');
    }

    public function owners()
    {
        return $this->morphedByMany(Owner::class, 'driver');
    }
}

由上面可知，belongToMany更换成了morphToMany，传入了driver字段。而Car model则更换成了morphedByMany，分别对应着不同的modelCopy

// 多数据处理
$valet->cars()->saveMany([$car1, $car2]);
$owner->cars()->saveMany([$car1, $car2]);

//单数据处理
$valet->cars()->save($car1);
$owner->cars()->save($car1);

//以下的处理方式不同
//多数据处理
$car->valets()->attach([
    $valet1->id,
    $valet2->id,
]);
$car->owners()->attach([
    $owner1->id,
    $owner2->id,
]);Copy

// 获取driver的相关cars
$valet->cars
$owner->cars
// 获取car的相关drivers
$car->owners
$car->valetsCopy