https://github.com/yuukanehiro/AlgorithmsDataStructure/blob/main/Sequence/ParentAccessChildContentsbyLoop.php

実務で良くあるアルゴリズム🐱

こういうのとか

$users = [
    [
        'id' => 1,
        'email' => '1@example.com',
        'profile_enable' => true,
    ],
    [
        'id' => 2,
        'email' => '2@example.com',
        'profile_enable' => false,
    ],
    [
        'id' => 3,
        'email' => '3@example.com',
        'profile_enable' => true,
    ],
];

$user_profiles = [
    [
        'id' => 1,
        'user_id' => 1,
        'name' => "優さん",
    ],
    [
        'id' => 2,
        'user_id' => 2,
        'name' => "佐藤",
    ],
    [
        'id' => 3,
        'user_id' => 3,
        'name' => "鈴木",
    ],
];

// 子を親のidでindexを指定して配列化
$profile_contents = [];
foreach ($user_profiles as $user_profile) {
    $profile_contents[$user_profile['user_id']] = $user_profile;
}

// 親のプロフィール設定が有効であれば出力
foreach ($users as $user) {
    if ($user['profile_enable']) {
        print_r($profile_contents[$user['id']]);
    }
}

// Array
// (
//     [id] => 1
//     [user_id] => 1
//     [name] => 優さん
// )
// Array
// (
//     [id] => 3
//     [user_id] => 3
//     [name] => 鈴木
// )

数が大きくなった重い処理を解消をする時に使える

public function getUsersSkillNames()
{
    $users = Users->all();
    $user_skill_names = [];
    foreach ($users as $user) {
        $user_profile = userProfile->where('user_id', $user->id);
        foreach($user_profile->skill_ids as $skill_id) {
            $user_skill_names[$user->id][] = Skill->where('id', $skill_id)->name;
        }
    }
    return $user_skill_names;
}

のようなn+1 な状況

解決する

連想配列で処理できるようにする

public function getUsersSkillNames()
{
    $skills = Skill->all();
    foreach ($skill_arrays as $skill) {
        $skill_names[$skill_id] = $skill->name;
    }
    $user_skill_ids = User::with('profiles')->pluck('skill_ids', 'user_id')->get()->toArray();
    // ここはすべて配列で処理できる
    $user_skill_names = [];
    foreach ($user_skill_ids as $user_id => $skill_ids) {
        foreach ($skill_ids as $skill_id) {
            $user_skill_names[$user->id][] = $skill_names[$skill_id]
        }
    }
    return $user_skill_names;
}

利用イメージ

$users_skill_names = $this->getUserSkillNames();
$guest_users = User->where('type', 'guest')->get();
foreach ($guest_users as $guest_user) {
    $user_skill_names = isset($user_skill_names[$guest_user->id]) ?? [];
}

解消できる🐱