What steps should be taken to ensure the correct operation of an application when changing a field type from int to string in the Room database?

When changing a field type from int to string in a Room database, a migration must be performed to preserve data and avoid errors.

Main steps:

1. Create a new version of the database with an updated schema where the field is changed to String.
2. Implement a Migration object, describing the logic to convert data from int to string. For example, create a new temporary table with the required schema, copy and convert data, delete the old table, and rename the temporary one.
3. Register the migration in RoomDatabase.Builder via the .addMigrations() method.

Migration example:

val MIGRATION_1_2 = object : Migration(1, 2) {
    override fun migrate(database: SupportSQLiteDatabase) {
        database.execSQL("CREATE TABLE new_table (id INTEGER PRIMARY KEY NOT NULL, field TEXT)")
        database.execSQL("INSERT INTO new_table (id, field) SELECT id, CAST(field AS TEXT) FROM old_table")
        database.execSQL("DROP TABLE old_table")
        database.execSQL("ALTER TABLE new_table RENAME TO old_table")
    }
}

4. Update the database version in the @Database annotation.

Thus, the application will be able to work correctly with the changed field type without data loss.