如何更新belonsToMany（值）？

Question

我有一张桌子social_user

如何保存value字段？

Controller

public function update(Request $request)
{
    $request->user()->update($request->except(['image', 'related_id', 'social_id']) + [
            'image' => $request->hasFile('image') ?
            $request->image->storeAs('images/users', time().'.'.$request->image->extension(), 'public') : null
        ]);

    $request->user()->socials()->sync($request->social_id);

    foreach ($request->value as $related){
        $request->user()->socials()->create(['value' => $related]);
    }
}

User.php

public function socials()
{
    return $this->belongsToMany(Social::class)->withPivot('value');
}