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Data Providers
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==============
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In the [Pagination](output-pagination.md) and [Sorting](output-sorting.md) sections, we have described how to
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allow end users to choose a particular page of data to display and sort them by some columns. Because the task
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of paginating and sorting data is very common, Yii provides a set of *data provider* classes to encapsulate it.
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A data provider is a class implementing [[yii\data\DataProviderInterface]]. It mainly supports retrieving paginated
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and sorted data. It is usually used to work with [data widgets](output-data-widgets.md) so that end users can
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interactively paginate and sort data.
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The following data provider classes are included in the Yii releases:
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* [[yii\data\ActiveDataProvider]]: uses [[yii\db\Query]] or [[yii\db\ActiveQuery]] to query data from databases
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and return them in terms of arrays or [Active Record](db-active-record.md) instances.
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* [[yii\data\SqlDataProvider]]: executes a SQL statement and returns database data as arrays.
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* [[yii\data\ArrayDataProvider]]: takes a big array and returns a slice of it based on the paginating and sorting
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specifications.
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The usage of all these data providers share the following common pattern:
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```php
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// create the data provider by configuring its pagination and sort properties
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$provider = new XyzDataProvider([
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'pagination' => [...],
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'sort' => [...],
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]);
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// retrieves paginated and sorted data
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$models = $provider->getModels();
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// get the number of data items in the current page
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$count = $provider->getCount();
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// get the total number of data items across all pages
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$totalCount = $provider->getTotalCount();
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```
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The `pagination` and `sort` properties of data providers correspond to the configurations for
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[[yii\data\Pagination]] and [[yii\data\Sort]], respectively.
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[Data widgets](output-data-widgets.md), such as [[yii\grid\GridView]], have a property named `dataProvider` which
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can take a data provider instance and display the data it provides. For example,
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```php
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echo yii\grid\GridView::widget([
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'dataProvider' => $dataProvider,
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]);
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```
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These data providers mainly vary in the way how the data source is specified. In the following subsections,
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we will explain the detailed usage of each of these data providers.
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## Active Data Provider <span id="active-data-provider"></span>
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To use [[yii\data\ActiveDataProvider]], you should configure its [[yii\data\ActiveDataProvider::query|query]] property.
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It can take either a [[yii\db\Query]] or [[yii\db\ActiveQuery]] object. If the former, the data returned will be arrays;
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if the latter, the data returned can be either arrays or [Active Record](db-active-record.md) instances.
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For example,
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```php
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use yii\data\ActiveDataProvider;
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$query = Post::find()->where(['status' => 1]);
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$provider = new ActiveDataProvider([
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'query' => Post::find(),
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'pagination' => [
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'pageSize' => 20,
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],
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'sort' => [
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'defaultOrder' => [
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'created_at' => SORT_DESC
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'title' => SORT_ASC,
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]
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],
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]);
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// returns an array of Post objects
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$posts = $provider->getModels();
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```
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If `$query` in the above example is created using the following code, then the data provider will return raw arrays.
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```php
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use yii\db\Query;
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$query = (new Query())->from('post')->where(['status' => 1]);
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```
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> Note: If a query already specifies the `orderBy` clause, the new ordering instructions given by end users
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(through the `sort` configuration) will be appended to the existing `orderBy` clause. Any existing `limit`
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and `offset` clauses will be overwritten by the pagination request from end users (through the `pagination` configuration).
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By default, [[yii\data\ActiveDataProvider]] uses the `db` application component as the database connection. You may
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use a different database connection by configuring the [[yii\data\ActiveDataProvider::db]] property. For example,
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## SQL Data Provider <span id="sql-data-provider"></span>
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Like other data providers, SqlDataProvider also supports sorting and pagination. It does so by modifying the given
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[[yii\data\SqlDataProvider::$sql]] statement with "ORDER BY" and "LIMIT" clauses. You may configure the
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[[yii\data\SqlDataProvider::$sort]] and [[yii\data\SqlDataProvider::$pagination]] properties to customize sorting
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and pagination behaviors.
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`SqlDataProvider` may be used in the following way:
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```php
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$count = Yii::$app->db->createCommand('
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SELECT COUNT(*) FROM user WHERE status=:status
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', [':status' => 1])->queryScalar();
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$dataProvider = new SqlDataProvider([
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'sql' => 'SELECT * FROM user WHERE status=:status',
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'params' => [':status' => 1],
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'totalCount' => $count,
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'sort' => [
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'attributes' => [
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'age',
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'name' => [
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'asc' => ['first_name' => SORT_ASC, 'last_name' => SORT_ASC],
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'desc' => ['first_name' => SORT_DESC, 'last_name' => SORT_DESC],
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'default' => SORT_DESC,
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'label' => 'Name',
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],
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],
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],
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'pagination' => [
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'pageSize' => 20,
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],
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]);
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// get the user records in the current page
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$models = $dataProvider->getModels();
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```
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> Note: if you want to use the pagination feature, you must configure the [[yii\data\SqlDataProvider::$totalCount]]
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property to be the total number of rows (without pagination). And if you want to use the sorting feature,
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you must configure the [[yii\data\SqlDataProvider::$sort]] property so that the provider knows which columns can
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be sorted.
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## Array Data Provider <span id="array-data-provider"></span>
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ArrayDataProvider implements a data provider based on a data array.
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The [[yii\data\ArrayDataProvider::$allModels]] property contains all data models that may be sorted and/or paginated.
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ArrayDataProvider will provide the data after sorting and/or pagination.
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You may configure the [[yii\data\ArrayDataProvider::$sort]] and [[yii\data\ArrayDataProvider::$pagination]] properties to
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customize the sorting and pagination behaviors.
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Elements in the [[yii\data\ArrayDataProvider::$allModels]] array may be either objects (e.g. model objects)
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or associative arrays (e.g. query results of DAO).
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Make sure to set the [[yii\data\ArrayDataProvider::$key]] property to the name of the field that uniquely
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identifies a data record or false if you do not have such a field.
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Compared to `ActiveDataProvider`, `ArrayDataProvider` could be less efficient
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because it needs to have [[yii\data\ArrayDataProvider::$allModels]] ready.
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ArrayDataProvider may be used in the following way:
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```php
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$query = new Query();
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$provider = new ArrayDataProvider([
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'allModels' => $query->from('post')->all(),
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'sort' => [
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'attributes' => ['id', 'username', 'email'],
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],
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'pagination' => [
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'pageSize' => 10,
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],
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]);
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// get the posts in the current page
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$posts = $provider->getModels();
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```
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> Note: if you want to use the sorting feature, you must configure the [[sort]] property
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so that the provider knows which columns can be sorted.
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Implementing your own custom data provider
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------------------------------------------
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Yii allows you to introduce your own custom data providers. In order to do it you need to implement the following
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`protected` methods:
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- `prepareModels` that prepares the data models that will be made available in the current page and returns them as an array.
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- `prepareKeys` that accepts an array of currently available data models and returns keys associated with them.
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- `prepareTotalCount` that returns a value indicating the total number of data models in the data provider.
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Below is an example of a data provider that reads CSV efficiently:
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```php
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<?php
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class CsvDataProvider extends \yii\data\BaseDataProvider
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{
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/**
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* @var string name of the file to read
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*/
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public $filename;
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/**
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* @var string|callable name of the key column or a callable returning it
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*/
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public $key;
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/**
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* @var SplFileObject
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*/
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protected $fileObject; // SplFileObject is very convenient for seeking to particular line in a file
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/**
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* @inheritdoc
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*/
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public function init()
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{
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parent::init();
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// open file
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$this->fileObject = new SplFileObject($this->filename);
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}
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/**
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* @inheritdoc
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*/
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protected function prepareModels()
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{
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$models = [];
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$pagination = $this->getPagination();
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if ($pagination === false) {
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// in case there's no pagination, read all lines
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while (!$this->fileObject->eof()) {
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$models[] = $this->fileObject->fgetcsv();
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$this->fileObject->next();
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}
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} else {
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// in case there's pagination, read only a single page
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$pagination->totalCount = $this->getTotalCount();
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$this->fileObject->seek($pagination->getOffset());
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$limit = $pagination->getLimit();
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for ($count = 0; $count < $limit; ++$count) {
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$models[] = $this->fileObject->fgetcsv();
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$this->fileObject->next();
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}
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}
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return $models;
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}
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/**
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* @inheritdoc
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*/
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protected function prepareKeys($models)
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{
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if ($this->key !== null) {
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$keys = [];
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foreach ($models as $model) {
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if (is_string($this->key)) {
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$keys[] = $model[$this->key];
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} else {
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$keys[] = call_user_func($this->key, $model);
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}
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}
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return $keys;
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} else {
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return array_keys($models);
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}
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}
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/**
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* @inheritdoc
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*/
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protected function prepareTotalCount()
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{
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$count = 0;
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while (!$this->fileObject->eof()) {
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$this->fileObject->next();
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++$count;
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}
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return $count;
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}
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}
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```
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