Yii2 Check if table exists in migration

Question

I have created a migration, whichi should create tables for my database, and insert default admin user.

<?php

//use Yii;
use yii\db\Migration;
use yii\db\Schema;

/**
 * Class m180616_200856_create_tables
 */

require_once( __DIR__.'/../config.php');


class m180616_200856_create_tables extends Migration
{


    public function up()
    {

        if (Yii::$app->db->schema->getTable("users",true)===null) {
            $this->createTable('users', [
                'id' => $this->primaryKey(),
                'username' => $this->string(),
                'password' => $this->string(),
                'authKey' => $this->string(),
                'accessToken' => $this->string()
            ]);

            $this->insert('users',array(
                'username'=> SUPERUSER_LOGIN,
                'password' => md5(SUPERUSER_PASS ),
                'authKey' => 'key',
                'accessToken' => ''
            ));
        }
    }
    public function down()
    {
        echo "m180616_200856_create_tables cannot be reverted.\n";

        return false;
    }

}

When i run this migration, i get the error:

*** applying m180616_200856_create_tables
Exception 'yii\base\UnknownMethodException' with message 'Calling unknown method: yii\db\mysql\Schema::getTable()'

If i include use Yii i get the error:

*** applying m180616_200856_create_tables
PHP Warning 'yii\base\ErrorException' with message 'The use statement with non-compound name 'Yii' has no effect'

So it seems i cannot use Yii namespace inside migration, how can i check if table exists?

Answer 1

In migration you can check if table does not exist in this way:

$tableName = $this->db->tablePrefix . 'users';
if ($this->db->getTableSchema($tableName, true) === null) {

It will usually work the same as:

$tableName = Yii::$app->db->tablePrefix . 'users';
if (Yii::$app->db->getTableSchema($tableName, true) === null) {

And yes, you can use Yii in migrations, it just does not make any sense to import class from global namespace if you're already in global namespace.