think\Model::hasOne PHP Method

    public function hasOne($model, $foreignKey = '', $localKey = '', $alias = [], $joinType = 'INNER')
    {
        // 记录当前关联信息
        $model = $this->parseModel($model);
        $localKey = $localKey ?: $this->getPk();
        $foreignKey = $foreignKey ?: Loader::parseName($this->name) . '_id';
        return $this->relation()->hasOne($model, $foreignKey, $localKey, $alias, $joinType);
    }