计算 Laravel Eloquent 中所有根父节点的所有第 n 个子节点的数量
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【中文标题】计算 Laravel Eloquent 中所有根父节点的所有第 n 个子节点的数量【英文标题】：Count the number of all nth children of all the root parent in Laravel Eloquent 【发布时间】：2015-06-25 20:45:11 【问题描述】：我有一个来自 Laravel Eloquent 查询的集合。这里祖父有很多孩子（父亲），父亲有很多孩子（孙子）。 返回的结果是这样的：
[
"grand_father_id": "26",
"fathers": [
"father_id": "101",
"children": [
"child_id": "77",
"children_weight": [
"weight": "30.00",
]
,
"child_id": "84",
"children_weight": [
"weight": "20.00",
]
]
,
"father_id": "102",
"children": [
"child_id": "78",
"children_weight": [
"weight": "50.00",
]
]
]
,
"grand_father_id": "27",
"fathers": [
"father_id": "100",
"children": [
"child_id": "83",
"children_weight": [
"weight": "100.00",
]
]
]
,
"grand_father_id": "28",
"fathers": [
"father_id": "105",
"children": [
"child_id": "81",
"children_weight": [
"weight": "80.00",
]
,
"child_id": "82",
"children_weight": [
"weight": "0.00",
]
]
]
,
"grand_father_id": "29",
"fathers": [
"father_id": "108",
"children": [
"child_id": "79",
"children_weight": [
"weight": "44.00",
]
,
"child_id": "80",
"children_weight": [
"weight": "56.00",
]
]
]
,
"grand_father_id": "30",
"fathers": [
"father_id": "107",
"children": [
]
]
]
我如何计算所有祖父的所有孙子的总数。我当然可以使用嵌套循环来计算这个。但是还有其他 Laravel Collection 方法可以做到这一点吗？顺便说一句，我在这里举的祖父、父亲、孙子的例子只是一个假名的例子。真正的字段是objectives、actions、success_indicators、success_indicator_weight。获取集合的查询是：
return Objective::with([
'actions' => function($query)
$query->select(['action_id', 'action_description', 'objective_id_fk']);
, 'actions.successIndicators' => function($query)
$query->select('success_indicator_id', 'success_indicator_description', 'action_id_fk');
, 'actions.successIndicators.SuccessIndicatorYearWeight' => function($query)
$query->select('success_indicator_weight', 'success_indicator_unit', 'success_indicator_id_fk');
,
])->get()
【问题讨论】：
【参考方案1】：有很多 array_* 辅助方法可用于对嵌套数组执行各种操作，但我认为没有任何东西可以满足您的需求。你可以自己检查 - http://laravel.com/docs/5.0/helpers#arrays
我不知道 Collection 是否内置了任何东西，但您可以考虑每个 Grandfather 类的访问器方法：
class Grandfather extends Eloquent
...
public function getTotalGrandchildrenAttribute()
$total_grandchildren = 0;
// loop through each father
foreach ($this->fathers as $father)
$total_grandchildren += count($father->children);
return $total_grandchildren;
然后在你的脚本中：
$grandfathers = Grandfathers::all();
$total_grandchildren = 0;
foreach ($grandfathers as $grandfather)
$total_grandchildren += $grandfather->total_grandchildren;
echo "Total grandchildren: $total_grandchildren";
http://laravel.com/docs/5.0/eloquent#accessors-and-mutators
此外，您可能希望使用with('fathers') 和with('children') 而不是使用上面显示的 all()，这样您就不会在每次想要获取父亲/孩子时都访问数据库：
$grandfathers = Grandfathers::with(array('fathers' => function($query)
$query->with('children');
);
http://laravel.com/docs/5.0/eloquent#eager-loading
【讨论】：
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