Trait yii\db\ActiveRelationTrait

                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]];
    }
}

            

                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();
}

            

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

            

                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;
}

            

                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;
}