Background first on my question. A user hasMany contacts and a contact hasMany anniversaries. I want to filter the upcoming anniversaries. So far I have this:

$filtered = auth()->user()->contacts()->get()->each(function ($contact) {
    $contact->anniversaries->filter(function ($anniversary) {

        // return true or false based on a method on the anniversary model
        return $anniversary->method() == true;

    });
});

But this just returns all the contacts (obviously) with all their anniversaries, and I wish to exclude the ones that are false when calling the $anniversary->method().

Whatever is in the $anniversary->method() is not important, this just returns a true or false.

When I do the following, it works:

$collection = auth()->user()->anniversaries()->get();

$filtered = $collection->filter(function ($anniversary) {
    return $anniversary->method() == true;
});

I get only the anniversaries from where the $anniversary->method() is indeed true.

My question is mainly, why does this happen, I only want to understand it, not so much need an answer on how to make it work. Thanks in advance for any insights!

CodePudding user response：

In the first example, you are only filtering the anniversaries of each contact. You are not filtering the contacts directly per see.

$filtered = auth()->user()->contacts()->get()->each(function ($contact) {
    // You are filtering only the anniversaries of each contact
    $anniversaries = $contact->anniversaries->filter(function ($anniversary) {
        return $anniversary->method() == true;

    });

    // over here you should get the same as in your second example
    dd($anniversaries);
});

In your second example you are doing the following pseudo-code:

1. Fetch all anniversaries of each user
2. Filter the anniversaries that matches $anniversary->method() === true

To get the same results in the first example you would have to use a combination of filter with ->count()

$filtered = auth()->user()->contacts()->get()->filter(function ($contact) {
    $filteredByMethod = $contact->anniversaries->filter(function ($anniversary) {

        // return true or false based on a method on the anniversary model
        return $anniversary->method() == true;
    });

    return $filteredByMethod->count() > 0;
});

Which one is more performant is beyond the scope of this answer.

Quick tip

The method filter from Laravel's collections needs to return a truthy value to be filtered by. Since your method returns true or false you can just call the method directly without comparing with true:

$collection = auth()->user()->anniversaries()->get();

$filtered = $collection->filter(function ($anniversary) {
    return $anniversary->method();
});