Lazy Collections · October Cms 筆記

## Lazy Collections ### 介紹 > **注意：**在詳細了解October的惰性集合之前，請花一些時間來熟悉[PHP生成器](https://www.php.net/manual/en/language.generators.overview.php)。為了補充已經強大的`Collection`類，`LazyCollection`該類利用PHP的[生成器](https://www.php.net/manual/en/language.generators.overview.php)來允許您處理非常大的數據集，同時保持較低的內存使用率。例如，假設您的應用程序需要處理一個千兆字節的日志文件，同時利用October的收集方法來解析日志。懶惰的收集可以用來在給定的時間僅將一小部分文件保留在內存中，而不是一次將整個文件讀入內存： ~~~ use App\LogEntry; use Illuminate\Support\LazyCollection; LazyCollection::make(function () { $handle = fopen('log.txt', 'r'); while (($line = fgets($handle)) !== false) { yield $line; } })->chunk(4)->map(function ($lines) { return LogEntry::fromLines($lines); })->each(function (LogEntry $logEntry) { // Process the log entry... }); ~~~ 或者，假設您需要遍歷10,000個Eloquent模型。使用傳統的October集合時，必須同時將所有10,000個Eloquent模型加載到內存中： ~~~ $users = App\User::all()->filter(function ($user) { return $user->id > 500; }); ~~~ 但是，查詢生成器的`cursor`方法返回一個`LazyCollection`實例。這樣，您仍然可以只對數據庫運行單個查詢，也可以一次僅將一個Eloquent模型加載到內存中。在此示例中，在`filter`我們實際逐個迭代每個用戶之前，不會執行回調，從而大大減少了內存使用量： ~~~ $users = App\User::cursor()->filter(function ($user) { return $user->id > 500; }); foreach ($users as $user) { echo $user->id; } ~~~ ### [](https://octobercms.com/docs/services/collections#creating-lazy-collections)創建惰性集合要創建一個懶惰的集合實例，您應該將PHP生成器函數傳遞給集合的`make`方法： ~~~ use Illuminate\Support\LazyCollection; LazyCollection::make(function () { $handle = fopen('log.txt', 'r'); while (($line = fgets($handle)) !== false) { yield $line; } }); ~~~ ### [](https://octobercms.com/docs/services/collections#the-enumerable-contract)無數合同 `Collection`該類上幾乎所有可用的方法也都可用`LazyCollection`。這兩個類都實現了`Illuminate\Support\Enumerable`合同，該合同定義了以下方法： [所有](https://octobercms.com/docs/services/collections#method-all)[平均](https://octobercms.com/docs/services/collections#method-average)[平均](https://octobercms.com/docs/services/collections#method-avg)[大塊](https://octobercms.com/docs/services/collections#method-chunk)[崩塌](https://octobercms.com/docs/services/collections#method-collapse)[收集](https://octobercms.com/docs/services/collections#method-collect)[相結合](https://octobercms.com/docs/services/collections#method-combine)[的concat](https://octobercms.com/docs/services/collections#method-concat)[包含](https://octobercms.com/docs/services/collections#method-contains)[containsStrict](https://octobercms.com/docs/services/collections#method-containsstrict)[計數](https://octobercms.com/docs/services/collections#method-count)[countBy](https://octobercms.com/docs/services/collections#method-countBy)[CROSSJOIN](https://octobercms.com/docs/services/collections#method-crossjoin)[DD](https://octobercms.com/docs/services/collections#method-dd)[差異](https://octobercms.com/docs/services/collections#method-diff)[diffAssoc](https://octobercms.com/docs/services/collections#method-diffassoc)[diffKeys](https://octobercms.com/docs/services/collections#method-diffkeys)[轉儲](https://octobercms.com/docs/services/collections#method-dump)[重復](https://octobercms.com/docs/services/collections#method-duplicates)[duplicatesStrict](https://octobercms.com/docs/services/collections#method-duplicatesstrict)[每個](https://octobercms.com/docs/services/collections#method-each)[eachSpread](https://octobercms.com/docs/services/collections#method-eachspread)[每](https://octobercms.com/docs/services/collections#method-every)[除了](https://octobercms.com/docs/services/collections#method-except)[過濾器](https://octobercms.com/docs/services/collections#method-filter)[第一](https://octobercms.com/docs/services/collections#method-first)[firstWhere](https://octobercms.com/docs/services/collections#method-first-where)[flatMap](https://octobercms.com/docs/services/collections#method-flatmap)[壓扁](https://octobercms.com/docs/services/collections#method-flatten)[翻轉](https://octobercms.com/docs/services/collections#method-flip)[forPage](https://octobercms.com/docs/services/collections#method-forpage)[GET](https://octobercms.com/docs/services/collections#method-get)[GROUPBY](https://octobercms.com/docs/services/collections#method-groupby)[有](https://octobercms.com/docs/services/collections#method-has)[破滅](https://octobercms.com/docs/services/collections#method-implode)[相交](https://octobercms.com/docs/services/collections#method-intersect)[intersectByKeys](https://octobercms.com/docs/services/collections#method-intersectbykeys)[的isEmpty](https://octobercms.com/docs/services/collections#method-isempty)[isNotEmpty](https://octobercms.com/docs/services/collections#method-isnotempty)[加入](https://octobercms.com/docs/services/collections#method-join)[keyBy](https://octobercms.com/docs/services/collections#method-keyby)[鍵](https://octobercms.com/docs/services/collections#method-keys)[最后](https://octobercms.com/docs/services/collections#method-last)[宏觀](https://octobercms.com/docs/services/collections#method-macro)[化妝](https://octobercms.com/docs/services/collections#method-make)[地圖](https://octobercms.com/docs/services/collections#method-map)[mapInto](https://octobercms.com/docs/services/collections#method-mapinto)[mapSpread](https://octobercms.com/docs/services/collections#method-mapspread)[mapToGroups](https://octobercms.com/docs/services/collections#method-maptogroups)[mapWithKeys](https://octobercms.com/docs/services/collections#method-mapwithkeys)[最大](https://octobercms.com/docs/services/collections#method-max)[位數](https://octobercms.com/docs/services/collections#method-median)[合并](https://octobercms.com/docs/services/collections#method-merge)[mergeRecursive](https://octobercms.com/docs/services/collections#method-mergerecursive)[分鐘](https://octobercms.com/docs/services/collections#method-min)[模式](https://octobercms.com/docs/services/collections#method-mode)[第n](https://octobercms.com/docs/services/collections#method-nth)[只](https://octobercms.com/docs/services/collections#method-only)[墊](https://octobercms.com/docs/services/collections#method-pad)[分區](https://octobercms.com/docs/services/collections#method-partition)[管](https://octobercms.com/docs/services/collections#method-pipe)[勇氣](https://octobercms.com/docs/services/collections#method-pluck)[隨機](https://octobercms.com/docs/services/collections#method-random)[降低](https://octobercms.com/docs/services/collections#method-reduce)[拒絕](https://octobercms.com/docs/services/collections#method-reject)[更換](https://octobercms.com/docs/services/collections#method-replace)[replaceRecursive](https://octobercms.com/docs/services/collections#method-replacerecursive)[反向](https://octobercms.com/docs/services/collections#method-reverse)[搜索](https://octobercms.com/docs/services/collections#method-search)[洗牌](https://octobercms.com/docs/services/collections#method-shuffle)[跳過](https://octobercms.com/docs/services/collections#method-skip)[切片](https://octobercms.com/docs/services/collections#method-slice)[一些](https://octobercms.com/docs/services/collections#method-some)[排序](https://octobercms.com/docs/services/collections#method-sort)[sortBy](https://octobercms.com/docs/services/collections#method-sortby)[sortByDesc](https://octobercms.com/docs/services/collections#method-sortbydesc)[SORTKEYS](https://octobercms.com/docs/services/collections#method-sortkeys)[sortKeysDesc](https://octobercms.com/docs/services/collections#method-sortkeysdesc)[分裂](https://octobercms.com/docs/services/collections#method-split)[和](https://octobercms.com/docs/services/collections#method-sum)[取](https://octobercms.com/docs/services/collections#method-take)[自來水](https://octobercms.com/docs/services/collections#method-tap)[倍](https://octobercms.com/docs/services/collections#method-times)[指定者](https://octobercms.com/docs/services/collections#method-toarray)[的toJSON](https://octobercms.com/docs/services/collections#method-tojson)[工會](https://octobercms.com/docs/services/collections#method-union)[獨特](https://octobercms.com/docs/services/collections#method-unique)[uniqueStrict](https://octobercms.com/docs/services/collections#method-uniquestrict)[除非](https://octobercms.com/docs/services/collections#method-unless)[unlessEmpty](https://octobercms.com/docs/services/collections#method-unlessempty)[unlessNotEmpty](https://octobercms.com/docs/services/collections#method-unlessnotempty)[解包](https://octobercms.com/docs/services/collections#method-unwrap)[的值](https://octobercms.com/docs/services/collections#method-values)[時](https://octobercms.com/docs/services/collections#method-when)[whenEmpty](https://octobercms.com/docs/services/collections#method-whenempty)[whenNotEmpty](https://octobercms.com/docs/services/collections#method-whennotempty)[其中](https://octobercms.com/docs/services/collections#method-where)[whereStrict](https://octobercms.com/docs/services/collections#method-wherestrict)[whereBetween](https://octobercms.com/docs/services/collections#method-wherebetween)[其中](https://octobercms.com/docs/services/collections#method-wherein)[whereInStrict](https://octobercms.com/docs/services/collections#method-whereinstrict)[whereInstanceOf](https://octobercms.com/docs/services/collections#method-whereinstanceof)[whereNotBetween](https://octobercms.com/docs/services/collections#method-wherenotbetween)[whereNotIn](https://octobercms.com/docs/services/collections#method-wherenotin)[whereNotInStrict](https://octobercms.com/docs/services/collections#method-wherenotinstrict)[渦卷](https://octobercms.com/docs/services/collections#method-wrap)[拉鏈](https://octobercms.com/docs/services/collections#method-zip) > **注：**方法是變異的集合（如`shift`，`pop`，`prepend`等）都*無法*提供的`LazyCollection`類。 ### [](https://octobercms.com/docs/services/collections#lazy-collection-methods)延遲收集方法除了`Enumerable`合同中定義的方法外，`LazyCollection`該類還包含以下方法： #### [](https://octobercms.com/docs/services/collections#method-tapEach)`tapEach()` 盡管該`each`方法立即為集合中的每個項目調用給定的回調，但是該`tapEach`方法僅調用給定的回調，因為這些項目正被逐一從列表中拉出： ~~~ $lazyCollection = LazyCollection::times(INF)->tapEach(function ($value) { dump($value); }); // Nothing has been dumped so far... $array = $lazyCollection->take(3)->all(); ~~~ #### [](https://octobercms.com/docs/services/collections#method-remember)`remember()` 該`remember`方法返回一個新的惰性集合，該集合將記住已枚舉的所有值，并且在再次枚舉該集合時將不會再次檢索它們： ~~~ $users = User::cursor()->remember(); // No query has been executed yet... $users->take(5)->all(); // The query has been executed and the first 5 users have been hydrated from the database... $users->take(20)->all(); // First 5 users come from the collection's cache... The rest are hydrated from the database... ~~~