Download iOS/SQLite (Powerpoint)

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.
• Apps do not share Embedded Databases the
way they share databases like Oracle and DB2.
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
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
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
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];
Opening the Database
• before you can use the database it must be
opened.
if (![db open]) {
[db release];
return;}
• fails – insufficient resources, permissions
Closing the Database
• Close the FMDatabase connection when you
are done with it. SQLite will then relinquish
and resources it has acquired.
[db close]
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 ( ?)"]
Select
• [FMDatabase executeQuery]
• Query results come back in an FMResultSet
• Ex
FMResultSet * s = [db executeQuery:@"SELECT * FROM mytable"];
while ([s next]) {
// retrieve the values
}
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.
FMResultSet data retrieval
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intForColumn
longForColumn
longLongIntForColumn
boolForColumn
doubleForColumn
stringForColumn
dateForColumn
dataForColumn
dataNoCopyForColumn
UTF8StringForColumnIndex
objectForColumn