关于laravel5.4.12新增集合操作when方法详解

$hosts = [
 ['name' => 'Eric Barnes', 'location' => 'USA', 'is_active' => 0],
 ['name' => 'Jack Fruh', 'location' => 'USA', 'is_active' => 0],
 ['name' => 'Jacob Bennett', 'location' => 'USA', 'is_active' => 1],
 ['name' => 'Michael Dyrynda', 'location' => 'AU', 'is_active' => 1],
];

$inUsa = collect($hosts)->where('location', 'USA');
if (request('retired')) {
 $inUsa = $inUsa->filter(function($employee){
 return ! $employee['is_active'];
 });
}

$inUsa = collect($hosts)
 ->where('location', 'USA')
 ->when(request('retired'), function($collection) {
 return $collection->reject(function($employee){
 return $employee['is_active'];
 });
 });