Laravel - 如何从嵌套关系中提取字段

Question

I'm trying to pluck field from nested relations.

My class structure is:

User      hasMany       GroupUser
GroupUser belongsTo     Group
Group     belongsToMany Promotion

So this way I can get fine get Promotions from an User

$user->groupUsers()->with('group')->with('group.promotions')->get();

{
  "id": 4,
  ....
  "promotions": [
    {
      "id": 3,
      "group_id": 11,
      "user_id": 4,
      ...
      "group": {
        "id": 11,
        ...
        "promotions": [
          {
            "id": 8,
            "title": "Lavagem Mensal 1 unid.",
            "const": "LAVAGEM_MENSAL1_UNID",
            "pivot": {
              "group_id": 11,
              "promotion_id": 8
            }
          }
        ]
      }
    }
  ]
}

So what I need is to get a pluck list of Promotions.const .

Tried this way but it returns [null]

$user->groupUsers()->with('group')->with('group.promotions')->get()->pluck('group.promotions.const');

UPDATE: Now this way I close to achieve it.

$user->groupUsers()->with('group')->with('group.promotions')->get()->pluck('group.promotions.*.const');

"promotions": [
  [
    "BRF_LAVAGEM_MENSAL_1_UNID"
  ]
]

Just need to flat this array.

Answer 1

Try this:

$user->groupUsers()
    ->with('group.promotions')
    ->get()
    ->pluck('group.promotions.*.const')
    ->collapse();