laravel caching return 0 - laravel

Question

I am trying to cache request for counting number of users in different categories
my function without caching:
public function getNumOfUsersInCat()
{
$numUsers = count($this -> users);
$otherCategories = Category::where('id', '<>', $this -> id) -> get();
foreach($otherCategories as $categ){
if($this -> isAncestorOf($categ))
$numUsers += count($categ -> users);
}
return $numUsers;
}
I was trying to cache requests like:
public function getNumOfUsersInCat()
{
$numUsers = count($this -> users);
$otherCategories = Cache::remember('cache_numuserscat)',60*60*12,function(){
return
Category::where('id', '<>', $this -> id) -> get();
foreach($otherCategories as $categ){
if($this -> isAncestorOf($categ))
$numUsers += count($categ -> users);
}
});
return $numUsers;
}
But I am getting only 0
Laravel 5.7.2

Answer 1

It is because you have put the calculation loop inside your cache and before reaching that part, you return with the category list. So the code you run is actually this:
public function getNumOfUsersInCat()
{
$numUsers = count($this -> users);
$otherCategories = Cache::remember('cache_numuserscat)', 60*60*12, function(){
return Category::where('id', '<>', $this -> id) -> get();
});
return $numUsers;
}
Before the correct code, there are a few things you should note:
Your cache name should only work for this model you are in, so I added $this->id to the name.
You can use withCount to get the count of all model users in a single query. Your approach have N+1 problem.
The Final code can be like this:
public function getNumOfUsersInCat()
{
$cacheName = "cache_num_users_cat_" . $this->id;
return Cache::remember($cacheName, 60 * 60 * 12, function() {
$numUsers = count($this->users);
$otherCategories = Category::query()
->where('id', '<>', $this->id)
->withCount('users')
->get();
foreach ($otherCategories as $categ) {
if ($this->isAncestorOf($categ)) {
$numUsers += $categ->users_count;
}
}
return $numUsers;
});
}