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iOS/SQLite

iOS/SQLite. CS328 Dick Steflik. Embedded Databases. SQLite is the embedded database of choice for both the iOS and Android mobile platforms SQLite is called an embedded database because its primary use is to provide data persistence to your app, it is an integral part of your app.

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iOS/SQLite

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  1. iOS/SQLite CS328 Dick Steflik

  2. Embedded Databases • SQLite is the embedded database of choice for both the iOS and Android mobile platforms • SQLite is called an embedded database because its primary use is to provide data persistence to your app, it is an integral part of your app. • Apps do not share Embedded Databases the way they share databases like Oracle and DB2.

  3. Application Access to SQLite • Core Data • an Apple provided Object-Relational Mapping framework • stores Objective-C objects into a SQLite Database • object instance data looks like a row in an SQL table. • Flying Meat Database (FMDB) • FMDB is a set of Objective C wrappers for SQLite • let you program using embedded SQL • modeled after Java JDBC

  4. Core Data • Benefits • supported by Apple • don't need to know SQL • Drawbacks • does not work with RDBMS as the store • ordered relationships are hard • undo/rollback doesn't always work • data migration to a revised model is hard

  5. FMDB • Two main classes: • FMDatabase • represents a single SQLite database, used for executing SQL statements • FMResultSet • represents the results of executing a query on an FMDataBase

  6. Database Creation • Persistent and temporary databases can be created • Permanent at some file system path:FMDatabase * mydb = [FMDatabase databaseWithPath:@"/var/mydb.db"]; • Empty database at a temp location, database is deleted when it is closed:FMDatabase * mydb = [FMDatabase databaseWithPath:@""]; • In memory database created destroyed when database connection is closed: • FMDatabase * mydb = [FMDatabase databaseWithPath:NULL];

  7. Opening the Database • before you can use the database it must be opened. if (![db open]) { [db release]; return;} • fails – insufficient resources, permissions

  8. Closing the Database • Close the FMDatabase connection when you are done with it. SQLite will then relinquish and resources it has acquired.[db close]

  9. Executing Updates • [FMDatabase executeUpdate] • use this method to execute all SQL statements except SELECT. • returns a bool, yes is a good return, no is not • Ex[db executeUpdate:@"INSERT INTO mytable VALUES ( ?)"]

  10. Select • [FMDatabase executeQuery] • Query results come back in an FMResultSet • ExFMResultSet * s = [db executeQuery:@"SELECT * FROM mytable"];while ([s next]) { // retrieve the values}

  11. sqlite3.h • This .h file is on your MAC where you installed SQLite, it is the C language interface to SQLite. It can be used in place of FMDB. • The documentation in sqlite3.h is excellent.

  12. FMResultSet data retrieval • intForColumn • longForColumn • longLongIntForColumn • boolForColumn • doubleForColumn • stringForColumn • dateForColumn • dataForColumn • dataNoCopyForColumn • UTF8StringForColumnIndex • objectForColumn

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