Objective C Database Versioning from AppDelegate

gistfile1.m

//AppDelegate.h
@property(nonatomic,assign) NSArray *documentPaths;
@property(nonatomic,assign) NSError *error;
@property(nonatomic,assign) NSFileManager *fileManager;
@property(nonatomic,assign) NSString *documentsDir;

//AppDelegate.m
@synthesize error, fileManager, documentPaths, documentsDir;

...

- (id) init
{	
...

    // copy databases if they don't exist
    fileManager = [NSFileManager defaultManager];
    documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    documentsDir = [documentPaths objectAtIndex: 0];
    
    [self copyFileFromBundleToDocs: @"Favorites": false]; // no version checking
    [self copyFileFromBundleToDocs: @"Inventory": true]; // version checking enabled
    // copy databases end
 
...
}

#pragma mark
#pragma mark database versioning

-(void)fileOperationErrorHandler: (NSString*) source {
    NSLog(@"\n***** %@ error description - %@", source, [error localizedDescription]);
    NSLog(@"***** %@ error reason - %@\n", source, [error localizedFailureReason]);
}

-(BOOL)copyFile: (NSString*)fileName: (NSString*)fileType {
    error = nil;
    if ([fileManager copyItemAtPath: [[NSBundle mainBundle] pathForResource: fileName ofType: fileType]
                             toPath: [documentsDir stringByAppendingPathComponent: fileName]
                              error: &error]) {
        NSLog(@"Successfully copied %@ to %@.", fileName, documentsDir);
        return true;
    } else {
        [self fileOperationErrorHandler: @"copyFile"];
        return false;
    }
}

-(BOOL)deleteFile: (NSString*)fileName {
    error = nil;
    if ([fileManager removeItemAtPath: [documentsDir stringByAppendingPathComponent: fileName]
                                error: &error]) {
        NSLog (@"Deleted %@.", fileName);
        return true;
    } else {
        [self fileOperationErrorHandler: @"deleteFile"];
        return false;
    }
}

-(BOOL)fileExists: (NSString*)fileName {
    return [fileManager fileExistsAtPath: [documentsDir stringByAppendingPathComponent: fileName]];
}

-(NSString*)readDataFromFile: (NSString*)fileName {
    NSString *filePath = [documentsDir stringByAppendingPathComponent: fileName];
    NSString *data = nil;
    
    error = nil;
    if ([self fileExists: fileName]) {
        data = [NSString stringWithContentsOfFile: filePath
                                         encoding: NSUTF8StringEncoding
                                            error: &error];
        if (error == nil) {
            NSLog (@"Read '%@' from %@.", data, fileName);
        } else {
            [self fileOperationErrorHandler: @"readVersionFromFile"];
            data = nil;
        }
    }
    return data;
}

-(bool)writeDataToFile: (NSString*) fileName: (NSString*) data {
    error = nil;
    if ([fileManager createFileAtPath: [documentsDir stringByAppendingPathComponent: fileName]
                             contents: [data dataUsingEncoding: NSUTF8StringEncoding]
                           attributes: nil]) {
        NSLog (@"Wrote '%@' to %@.", data, fileName);
        return true;
    } else {
        [self fileOperationErrorHandler: @"copyFile"];
        return false;
    }
}

-(void)copyFileFromBundleToDocs: (NSString*)fileName: (BOOL)versionCheck {
    NSDictionary *info = [[NSBundle mainBundle] infoDictionary];
    NSString *bundleVerson = [NSString stringWithFormat: @"%@ (%@)", [info objectForKey: @"CFBundleShortVersionString"], [info objectForKey: @"CFBundleVersion"]];
    NSString *fileVersion = nil;
    NSString *versionFileName = [NSString stringWithFormat: @"%@.version", fileName];
    
    if ([self fileExists: fileName]) {
        
        // db file exists
        NSLog (@"%@ found.", fileName);
        
        if (versionCheck) {
            
            // compare version/build number with current values
            NSLog (@"Checking version.");
            fileVersion = [self readDataFromFile: versionFileName];
            NSLog(@"(bundleVerson: %@ == fileVersion: %@) => %@", bundleVerson, fileVersion, [fileVersion isEqualToString: bundleVerson] ? @"true" : @"false");
            
            // new db file in app bundle
            if (! [fileVersion isEqualToString: bundleVerson]) {
                
                // delete db file in documnets
                if ([self deleteFile: fileName]) {
                    
                    // copy app bundle db file to documents
                    if ([self copyFile: fileName: @""]) {
                        
                        // write version/build number to the version file in the documents folder.
                        [self writeDataToFile: versionFileName: bundleVerson];
                    }
                }
            }
        }
    } else {
        // db file doesn't exist
        NSLog (@"%@ not found, copying.", fileName);
        
        // copy db file to documents
        if ([self copyFile: fileName: @""]) {
            
            if (versionCheck) {
                
                // write version/build number to the version file in the documents folder.
                [self writeDataToFile: versionFileName: bundleVerson];
            }
        }
    }
    NSLog(@"Done with %@.", fileName);
}