FMDatabase factory class. Handles the creation of an FMDatabase object. Creates a new database from a template resource if necessary.

FMDatabaseFactory.m

//
//  FMDatabaseFactory.m
//
//  Copyright (c) 2012 Andy Sherwood. All rights reserved.
//

#import "FMDatabaseFactory.h"
#import <FMDatabase.h>

@implementation FMDatabaseFactory
{
    NSString* _dbFileName;
    NSFileManager* _fileManager;
    NSSearchPathDirectory _searchPath;
}

- (id)initWithResourceFileName:(NSString*)dbFileName
                    searchPath:(NSSearchPathDirectory)searchPath
                andFileManager:(NSFileManager*)fileManager
{
    self = [super init];
    
    if (self)
    {
        _dbFileName = [dbFileName copy];
        _searchPath = searchPath;
        _fileManager = fileManager;
    }
    
    return self;
}

- (FMDatabase*)openDatabase
{
    NSError* error;
    NSString* path = [self databasePath];
    
    if (![_fileManager fileExistsAtPath:path])
    {
        NSLog(@"Deploying fresh database to: %@", path);
        
        BOOL success = [_fileManager copyItemAtPath:[self freshDatabasePath]
                                             toPath:path
                                              error:&error];
        
        if (!success)
            @throw [NSException exceptionWithName:@"Failed to create writeable database"
                                           reason:[error localizedDescription]
                                         userInfo:nil];
    }
    
    FMDatabase* db = [FMDatabase databaseWithPath:path];
    
    [db open];
    
    return db;
}

- (void)dropDatabase
{
    NSLog(@"Dropping database");
    
    NSError* error;
    NSString* path = [self databasePath];
    
    if ([_fileManager fileExistsAtPath:path])
    {
        BOOL success = [_fileManager removeItemAtPath:path
                                                error:&error];
        
        if (!success)
            @throw [NSException exceptionWithName:@"Failed to remove database"
                                           reason:[error localizedDescription]
                                         userInfo:nil];
    }
}

- (void)backupDatabase
{
    NSLog(@"Backing up database");
    
    NSError* error;
    NSString* path = [self databasePath];
    NSString* backupPath = [self backupDatabasePath];
    
    if ([_fileManager fileExistsAtPath:backupPath])
    {
        if (![_fileManager removeItemAtPath:backupPath error:&error])
            @throw [NSException exceptionWithName:@"Failed to delete backup database"
                                           reason:[error localizedDescription]
                                         userInfo:nil];
    }
    
    if ([_fileManager fileExistsAtPath:path])
    {
        if (![_fileManager copyItemAtPath:path toPath:backupPath error:&error])
            @throw [NSException exceptionWithName:@"Failed to backup database"
                                           reason:[error localizedDescription]
                                         userInfo:nil];
    }
    else
        @throw [NSException exceptionWithName:@"Database does not exist" reason:[error localizedDescription] userInfo:nil];
}

- (void)restoreDatabase
{
    NSLog(@"Restoring database");

    NSError* error;
    NSString* path = [self databasePath];
    NSString* backupPath = [self backupDatabasePath];
    
    if ([_fileManager fileExistsAtPath:path])
    {
        if (![_fileManager removeItemAtPath:path error:&error])
            @throw [NSException exceptionWithName:@"Failed to delete database" reason:[error localizedDescription] userInfo:nil];
    }
    
    if ([_fileManager fileExistsAtPath:backupPath])
    {
        if (![_fileManager copyItemAtPath:backupPath toPath:path error:&error])
            @throw [NSException exceptionWithName:@"Failed to restore database" reason:[error localizedDescription] userInfo:nil];
    }
    else
        @throw [NSException exceptionWithName:@"Backup database does not exist" reason:[error localizedDescription] userInfo:nil];
}

- (NSString*)databasePath
{
    NSArray* paths = NSSearchPathForDirectoriesInDomains(_searchPath, NSUserDomainMask, YES);
    NSString* documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory stringByAppendingPathComponent:_dbFileName];
}

- (NSString*)freshDatabasePath
{
    return [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:_dbFileName];
}

- (NSString*)backupDatabasePath
{
    NSString* path = [self databasePath];
    NSString* suffix = @"~backup";
    NSString* containingFolder = [path stringByDeletingLastPathComponent];
    NSString* fullFileName = [path lastPathComponent];
    NSString* fileExtension = [fullFileName pathExtension];
    NSString* fileName = [fullFileName stringByDeletingPathExtension];
    NSString* newFileName = [fileName stringByAppendingString:suffix];
    NSString* newFullFileName = [newFileName stringByAppendingPathExtension:fileExtension];
    
    return [containingFolder stringByAppendingPathComponent:newFullFileName];
}

@end