如何基于数据透视表Laravel获取数据计数？

Question

我有三个桌子，

     User                   cities             user_cities

id name    title           id   name        user_id   city_id
1   aaa   designer         1   cityA          2         1
2   bbb   developer        2   cityB          2         3
3   ccc   designer         3   cityC          1         2
4   ddd   designer                            3         3
5   rrr   developer                           3         2
                                              4         2
                                              4         3

现在，我将根据用户的title=designer对其进行过滤。则过滤器数据将为

     user

id name    title          
1   aaa   designer                
3   ccc   designer         
4   ddd   designer 

除了这些数据，我还必须获得像这样的城市的数量

data: {
   0: {
      name:cityB,
      id:2,
      count:3
    },
    1: {
      name:cityC,
      id:3,
      count:2
    }
}

我该如何用laravel雄辩地做到这一点？

Answer 1

你可以

$users = App\User::where('title', 'designer')->get();

并使用

foreach($users as $user) {
    $user->cities->count(); // collection count
}

但是更好的方法是Counting related models

$users = App\User::withCount('cities')->where('title', 'designer')->get();

然后

foreach($users as $user) {
    $user->cities_count; // relationship count
}