openDatabase function

Future<Database> openDatabase(
  1. String path,
  2. {int version,
  3. OnDatabaseConfigureFn onConfigure,
  4. OnDatabaseCreateFn onCreate,
  5. OnDatabaseVersionChangeFn onUpgrade,
  6. OnDatabaseVersionChangeFn onDowngrade,
  7. OnDatabaseOpenFn onOpen,
  8. bool readOnly = false,
  9. bool singleInstance = true}
)

Open the database at a given path

version (optional) specifies the schema version of the database being opened. This is used to decide whether to call onCreate, onUpgrade, and onDowngrade

The optional callbacks are called in the following order:

  1. onConfigure
  2. onCreate or onUpgrade or onDowngrade
  3. onOpen

onConfigure is the first callback invoked when opening the database. It allows you to perform database initialization such as enabling foreign keys or write-ahead logging

If version is specified, onCreate, onUpgrade, and onDowngrade can be called. These functions are mutually exclusive — only one of them can be called depending on the context, although they can all be specified to cover multiple scenarios

onCreate is called if the database did not exist prior to calling openDatabase. You can use the opportunity to create the required tables in the database according to your schema

onUpgrade is called if either of the following conditions are met:

  1. onCreate is not specified
  2. The database already exists and version is higher than the last database version

In the first case where onCreate is not specified, onUpgrade is called with its oldVersion parameter as 0. In the second case, you can perform the necessary migration procedures to handle the differing schema

onDowngrade is called only when version is lower than the last database version. This is a rare case and should only come up if a newer version of your code has created a database that is then interacted with by an older version of your code. You should try to avoid this scenario

onOpen is the last optional callback to be invoked. It is called after the database version has been set and before openDatabase returns

When readOnly (false by default) is true, all other parameters are ignored and the database is opened as-is

When singleInstance is true (the default), a single database instance is returned for a given path. Subsequent calls to openDatabase with the same path will return the same instance, and will discard all other parameters such as callbacks for that invocation.

Implementation

Future<Database> openDatabase(String path,
    {int version,
    OnDatabaseConfigureFn onConfigure,
    OnDatabaseCreateFn onCreate,
    OnDatabaseVersionChangeFn onUpgrade,
    OnDatabaseVersionChangeFn onDowngrade,
    OnDatabaseOpenFn onOpen,
    bool readOnly = false,
    bool singleInstance = true}) {
  final options = OpenDatabaseOptions(
      version: version,
      onConfigure: onConfigure,
      onCreate: onCreate,
      onUpgrade: onUpgrade,
      onDowngrade: onDowngrade,
      onOpen: onOpen,
      readOnly: readOnly,
      singleInstance: singleInstance);
  return databaseFactory.openDatabase(path, options: options);
}