# Trait yii\db\ActiveRelationTrait

Implemented by | yii\db\ActiveQuery, yii\elasticsearch\ActiveQuery, yii\mongodb\ActiveQuery, yii\mongodb\file\ActiveQuery, yii\redis\ActiveQuery, yii\sphinx\ActiveQuery
Available since version | 2.0
Source Code | https://github.com/yiisoft/yii2/blob/master/framework/db/ActiveRelationTrait.php

ActiveRelationTrait implements the common methods and properties for active record relational queries.

## Public Properties

Hide inherited properties

Property | Type | Description | Defined By
--- | --- | --- | ---
$inverseOf | string | The name of the relation that is the inverse of this relation. | yii\db\ActiveRelationTrait
$link | array | The columns of the primary and foreign tables that establish a relation. | yii\db\ActiveRelationTrait
$modelClass | yii\db\ActiveRecord |  | yii\db\ActiveRelationTrait
$multiple | boolean | Whether this query represents a relation to more than one record. | yii\db\ActiveRelationTrait
$primaryModel | yii\db\ActiveRecord | The primary model of a relational query. | yii\db\ActiveRelationTrait
$via | array|object | The query associated with the junction table. | yii\db\ActiveRelationTrait

## Public Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
__clone() | Clones internal objects. | yii\db\ActiveRelationTrait
all() | See yii\db\ActiveQueryInterface::all() for more info. | yii\db\ActiveRelationTrait
findFor() | Finds the related records for the specified primary record. | yii\db\ActiveRelationTrait
inverseOf() | Sets the name of the relation that is the inverse of this relation. | yii\db\ActiveRelationTrait
one() | See yii\db\ActiveQueryInterface::one() for more info. | yii\db\ActiveRelationTrait
populateRelation() | Finds the related records and populates them into the primary models. | yii\db\ActiveRelationTrait
via() | Specifies the relation associated with the junction table. | yii\db\ActiveRelationTrait

## Property Details

Hide inherited properties

$inverseOf public property

The name of the relation that is the inverse of this relation. For example, an order has a customer, which means the inverse of the "customer" relation is the "orders", and the inverse of the "orders" relation is the "customer". If this property is set, the primary record(s) will be referenced through the specified relation. For example, `$customer->orders[0]->customer` and `$customer` will be the same object, and accessing the customer of an order will not trigger new DB query. This property is only used in relational context.

See also inverseOf().

public string $inverseOf = null
$link public property

The columns of the primary and foreign tables that establish a relation. The array keys must be columns of the table for this relation, and the array values must be the corresponding columns from the primary table. Do not prefix or quote the column names as this will be done automatically by Yii. This property is only used in relational context.

public array $link = null
$modelClass public property
public yii\db\ActiveRecord $modelClass = null
$multiple public property

Whether this query represents a relation to more than one record. This property is only used in relational context. If true, this relation will populate all query results into AR instances using all(). If false, only the first row of the results will be retrieved using one().

public boolean $multiple = null
$primaryModel public property

The primary model of a relational query. This is used only in lazy loading with dynamic query options.

public yii\db\ActiveRecord $primaryModel = null
$via public property

The query associated with the junction table. Please call via() to set this property instead of directly setting it. This property is only used in relational context.

See also via().

public array|object $via = null

## Method Details

Hide inherited methods

__clone() public method

Clones internal objects.

public void __clone ( )

Source code

                    public function __clone()
    {
        parent::__clone();
        // make a clone of "via" object so that the same query object can be reused multiple times
        if (is_object($this->via)) {
            $this->via = clone $this->via;
        } elseif (is_array($this->via)) {
            $this->via = [$this->via[0], clone $this->via[1], $this->via[2]];
        }
    }

all() public method

See yii\db\ActiveQueryInterface::all() for more info.

public yii\db\ActiveRecordInterface[] all ( $db )
$db |  |
return | yii\db\ActiveRecordInterface[] |

findFor() public method

Finds the related records for the specified primary record.

This method is invoked when a relation of an ActiveRecord is being accessed lazily.

public mixed findFor ( $name, $model )
$name | string | The relation name
$model | yii\db\ActiveRecordInterface|yii\db\BaseActiveRecord | The primary model
return | mixed | The related record(s)
throws | yii\base\InvalidArgumentException | if the relation is invalid

Source code

                    public function findFor($name, $model)
    {
        if (method_exists($model, 'get' . $name)) {
            $method = new \ReflectionMethod($model, 'get' . $name);
            $realName = lcfirst(substr($method->getName(), 3));
            if ($realName !== $name) {
                throw new InvalidArgumentException('Relation names are case sensitive. ' . get_class($model) . " has a relation named \"$realName\" instead of \"$name\".");
            }
        }
        return $this->multiple ? $this->all() : $this->one();
    }

inverseOf() public method

Sets the name of the relation that is the inverse of this relation.

For example, a customer has orders, which means the inverse of the "orders" relation is the "customer". If this property is set, the primary record(s) will be referenced through the specified relation. For example, `$customer->orders[0]->customer` and `$customer` will be the same object, and accessing the customer of an order will not trigger a new DB query.

Use this method when declaring a relation in the yii\db\ActiveRecord class, e.g. in Customer model:

    public function getOrders()
    {
        return $this->hasMany(Order::class, ['customer_id' => 'id'])->inverseOf('customer');
    }

This also may be used for Order model, but with caution:

    public function getCustomer()
    {
        return $this->hasOne(Customer::class, ['id' => 'customer_id'])->inverseOf('orders');
    }

in this case result will depend on how order(s) was loaded. Let's suppose customer has several orders. If only one order was loaded:

    $orders = Order::find()->where(['id' => 1])->all();
    $customerOrders = $orders[0]->customer->orders;

variable `$customerOrders` will contain only one order. If orders was loaded like this:

    $orders = Order::find()->with('customer')->where(['customer_id' => 1])->all();
    $customerOrders = $orders[0]->customer->orders;

variable `$customerOrders` will contain all orders of the customer.

public $this inverseOf ( $relationName )
$relationName | string | The name of the relation that is the inverse of this relation.
return | $this | The relation object itself.

Source code

                    public function inverseOf($relationName)
    {
        $this->inverseOf = $relationName;
        return $this;
    }

one() public method

See yii\db\ActiveQueryInterface::one() for more info.

public yii\db\ActiveRecordInterface|array|null one ( $db )
$db |  |
return | yii\db\ActiveRecordInterface|array|null |

populateRelation() public method

Finds the related records and populates them into the primary models.

public array populateRelation ( $name, &$primaryModels )
$name | string | The relation name
$primaryModels | array | Primary models
return | array | The related models
throws | yii\base\InvalidConfigException | if $link is invalid

Source code

                    public function populateRelation($name, &$primaryModels)
    {
        if (!is_array($this->link)) {
            throw new InvalidConfigException('Invalid link: it must be an array of key-value pairs.');
        }
        if ($this->via instanceof self) {
            // via junction table
            /* @var $viaQuery ActiveRelationTrait */
            $viaQuery = $this->via;
            $viaModels = $viaQuery->findJunctionRows($primaryModels);
            $this->filterByModels($viaModels);
        } elseif (is_array($this->via)) {
            // via relation
            /* @var $viaQuery ActiveRelationTrait|ActiveQueryTrait */
            list($viaName, $viaQuery) = $this->via;
            if ($viaQuery->asArray === null) {
                // inherit asArray from primary query
                $viaQuery->asArray($this->asArray);
            }
            $viaQuery->primaryModel = null;
            $viaModels = array_filter($viaQuery->populateRelation($viaName, $primaryModels));
            $this->filterByModels($viaModels);
        } else {
            $this->filterByModels($primaryModels);
        }
        if (!$this->multiple && count($primaryModels) === 1) {
            $model = $this->one();
            $primaryModel = reset($primaryModels);
            if ($primaryModel instanceof ActiveRecordInterface) {
                $primaryModel->populateRelation($name, $model);
            } else {
                $primaryModels[key($primaryModels)][$name] = $model;
            }
            if ($this->inverseOf !== null) {
                $this->populateInverseRelation($primaryModels, [$model], $name, $this->inverseOf);
            }
            return [$model];
        }
        // https://github.com/yiisoft/yii2/issues/3197
        // delay indexing related models after buckets are built
        $indexBy = $this->indexBy;
        $this->indexBy = null;
        $models = $this->all();
        if (isset($viaModels, $viaQuery)) {
            $buckets = $this->buildBuckets($models, $this->link, $viaModels, $viaQuery);
        } else {
            $buckets = $this->buildBuckets($models, $this->link);
        }
        $this->indexBy = $indexBy;
        if ($this->indexBy !== null && $this->multiple) {
            $buckets = $this->indexBuckets($buckets, $this->indexBy);
        }
        $link = array_values($this->link);
        if (isset($viaQuery)) {
            $deepViaQuery = $viaQuery;
            while ($deepViaQuery->via) {
                $deepViaQuery = is_array($deepViaQuery->via) ? $deepViaQuery->via[1] : $deepViaQuery->via;
            };
            $link = array_values($deepViaQuery->link);
        }
        foreach ($primaryModels as $i => $primaryModel) {
            $keys = null;
            if ($this->multiple && count($link) === 1) {
                $primaryModelKey = reset($link);
                $keys = isset($primaryModel[$primaryModelKey]) ? $primaryModel[$primaryModelKey] : null;
            }
            if (is_array($keys)) {
                $value = [];
                foreach ($keys as $key) {
                    $key = $this->normalizeModelKey($key);
                    if (isset($buckets[$key])) {
                        if ($this->indexBy !== null) {
                            // if indexBy is set, array_merge will cause renumbering of numeric array
                            foreach ($buckets[$key] as $bucketKey => $bucketValue) {
                                $value[$bucketKey] = $bucketValue;
                            }
                        } else {
                            $value = array_merge($value, $buckets[$key]);
                        }
                    }
                }
            } else {
                $key = $this->getModelKey($primaryModel, $link);
                $value = isset($buckets[$key]) ? $buckets[$key] : ($this->multiple ? [] : null);
            }
            if ($primaryModel instanceof ActiveRecordInterface) {
                $primaryModel->populateRelation($name, $value);
            } else {
                $primaryModels[$i][$name] = $value;
            }
        }
        if ($this->inverseOf !== null) {
            $this->populateInverseRelation($primaryModels, $models, $name, $this->inverseOf);
        }
        return $models;
    }

via() public method

Specifies the relation associated with the junction table.

Use this method to specify a pivot record/table when declaring a relation in the yii\db\ActiveRecord class:

    class Order extends ActiveRecord
    {
       public function getOrderItems() {
           return $this->hasMany(OrderItem::class, ['order_id' => 'id']);
       }

       public function getItems() {
           return $this->hasMany(Item::class, ['id' => 'item_id'])
                       ->via('orderItems');
       }
    }

public $this via ( $relationName, callable $callable = null )
$relationName | string | The relation name. This refers to a relation declared in $primaryModel.
$callable | callable|null | A PHP callback for customizing the relation associated with the junction table. Its signature should be `function($query)`, where `$query` is the query to be customized.
return | $this | The relation object itself.

Source code

                    public function via($relationName, callable $callable = null)
    {
        $relation = $this->primaryModel->getRelation($relationName);
        $callableUsed = $callable !== null;
        $this->via = [$relationName, $relation, $callableUsed];
        if ($callable !== null) {
            call_user_func($callable, $relation);
        }
        return $this;
    }