Classes

The following classes are available globally.

  • A SQLite (https://sqlite.org/) Objective-C wrapper.

    Usage

    The three main classes in FMDB are:

    • FMDatabase - Represents a single SQLite database. Used for executing SQL statements.

    • FMResultSet - Represents the results of executing a query on an FMDatabase .

    • FMDatabaseQueue - If you want to perform queries and updates on multiple threads, you’ll want to use this class.

    See also

    External links

    Warning

    Do not instantiate a single FMDatabase object and use it across multiple threads. Instead, use FMDatabaseQueue .

    See more

    Declaration

    Objective-C

    @interface FMDatabase : NSObject

    Swift

    class FMDatabase : NSObject

  • Objective-C wrapper for sqlite3_stmt

    This is a wrapper for a SQLite sqlite3_stmt . Generally when using FMDB you will not need to interact directly with FMStatement, but rather with FMDatabase and FMResultSet only.

    See also

    See more

    Declaration

    Objective-C

    @interface FMStatement : NSObject {
  void *_statement;
  NSString *_query;
  long _useCount;
  BOOL _inUse;
}

    Swift

    class FMStatement : NSObject

  • Pool of FMDatabase objects.

    See also

    Warning

    Before using FMDatabasePool , please consider using FMDatabaseQueue instead.

    If you really really really know what you’re doing and FMDatabasePool is what you really really need (ie, you’re using a read only database), OK you can use it. But just be careful not to deadlock!

    For an example on deadlocking, search for: ONLY_USE_THE_POOL_IF_YOU_ARE_DOING_READS_OTHERWISE_YOULL_DEADLOCK_USE_FMDATABASEQUEUE_INSTEAD in the main.m file.

    See more

    Declaration

    Objective-C

    @interface FMDatabasePool : NSObject

    Swift

    class FMDatabasePool : NSObject

  • To perform queries and updates on multiple threads, you’ll want to use FMDatabaseQueue .

    Using a single instance of FMDatabase from multiple threads at once is a bad idea. It has always been OK to make a FMDatabase object per thread. Just don’t share a single instance across threads, and definitely not across multiple threads at the same time.

    Instead, use FMDatabaseQueue . Here’s how to use it:

    First, make your queue.

    FMDatabaseQueue *queue = [FMDatabaseQueue databaseQueueWithPath:aPath];

    Then use it like so:

    [queue inDatabase:^(FMDatabase *db) {
    [db executeUpdate:@"INSERT INTO myTable VALUES (?)", [NSNumber numberWithInt:1]];
    [db executeUpdate:@"INSERT INTO myTable VALUES (?)", [NSNumber numberWithInt:2]];
    [db executeUpdate:@"INSERT INTO myTable VALUES (?)", [NSNumber numberWithInt:3]];

    FMResultSet *rs = [db executeQuery:@"select * from foo"];
    while ([rs next]) {
        //…
    }
}];

    An easy way to wrap things up in a transaction can be done like this:

    [queue inTransaction:^(FMDatabase *db, BOOL *rollback) {
    [db executeUpdate:@"INSERT INTO myTable VALUES (?)", [NSNumber numberWithInt:1]];
    [db executeUpdate:@"INSERT INTO myTable VALUES (?)", [NSNumber numberWithInt:2]];
    [db executeUpdate:@"INSERT INTO myTable VALUES (?)", [NSNumber numberWithInt:3]];

    // if (whoopsSomethingWrongHappened) {
    //     *rollback = YES;
    //     return;
    // }

    // etc…
    [db executeUpdate:@"INSERT INTO myTable VALUES (?)", [NSNumber numberWithInt:4]];
}];

    FMDatabaseQueue will run the blocks on a serialized queue (hence the name of the class). So if you call FMDatabaseQueue ‘s methods from multiple threads at the same time, they will be executed in the order they are received. This way queries and updates won’t step on each other’s toes, and every one is happy.

    Warning

    Do not instantiate a single FMDatabase object and use it across multiple threads. Use FMDatabaseQueue instead.

    Warning

    The calls to FMDatabaseQueue ’s methods are blocking. So even though you are passing along blocks, they will not be run on another thread.

    @sa FMDatabase

    See more

    Declaration

    Objective-C

    @interface FMDatabaseQueue : NSObject

    Swift

    class FMDatabaseQueue : NSObject

  • Represents the results of executing a query on an FMDatabase .

    See also

    See more

    Declaration

    Objective-C

    @interface FMResultSet : NSObject

    Swift

    class FMResultSet : NSObject