问当iPhone中应用程序商店上的应用程序版本发生变化时，sqlite数据库会更新

EN

#define FirstTime 0

//if first time run of this version
if( [MyDataModel sharedInstance].count < (FirstTime + 1) )
{
    //do what you need to do as the first time load for this version

    [MyDataModel sharedInstance].count++
    //save the count value to disk so on next run you are not first time
    //this means count = 1
}

#define FirstTime 2

NSString * const VERSION_KEY = @"version";

-(void)upgradeDatabaseIfRequired{
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSString *previousVersion=[defaults objectForKey:VERSION_KEY];
    NSString *currentVersion=[self versionNumberString];

    if (previousVersion==nil || [previousVersion compare: currentVersion options: NSNumericSearch] == NSOrderedAscending) {
        // previous < current
        //read upgrade sqls from file
        NSString *plistPath = [[NSBundle mainBundle] pathForResource:@"UpgradeDatabase" ofType:@"plist"];
        NSArray *plist = [NSArray arrayWithContentsOfFile:plistPath];


        if (previousVersion==nil) {//perform all upgrades
            for (NSDictionary *dictionary in plist) {
                NSString *version=[dictionary objectForKey:@"version"];
                NSLog(@"Upgrading to v. %@", version);
                NSArray *sqlQueries=[dictionary objectForKey:@"sql"];
                while (![DB executeMultipleSql:sqlQueries]) {
                    NSLog(@"Failed to upgrade database to v. %@, Retrying...", version);
                };
            }
        }else{
            for (NSDictionary *dictionary in plist) {
                NSString *version=[dictionary objectForKey:@"version"];
                if ([previousVersion compare: version options: NSNumericSearch] == NSOrderedAscending) {
                    //previous < version
                    NSLog(@"Upgrading to v. %@", version);
                    NSArray *sqlQueries=[dictionary objectForKey:@"sql"];
                    while (![DB executeMultipleSql:sqlQueries]) {
                        NSLog(@"Failed to upgrade database to v. %@, Retrying...", version);
                    };
                }

            }
        }

        [defaults setObject:currentVersion forKey:VERSION_KEY];
        [defaults synchronize];
    }

}


- (NSString *)versionNumberString {
    NSDictionary *infoDictionary = [[NSBundle mainBundle] infoDictionary];
    NSString *majorVersion = [infoDictionary objectForKey:@"CFBundleShortVersionString"];
    return majorVersion;
}

- (void)isItTheFirstTimeAfterUpdate {
    NSString *versionnum;
    NSError *error;
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
                                                         NSUserDomainMask,
                                                         YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *path = [documentsDirectory stringByAppendingPathComponent:@"yourplist.plist"];
    NSFileManager *fileManager = [NSFileManager defaultManager];

    if(![fileManager fileExistsAtPath:path]) {
        NSString *bundle = [[NSBundle mainBundle] pathForResource:@"yourplist" ofType:@"plist"];
        [fileManager copyItemAtPath:bundle toPath:path error:&error];
    }

    NSMutableDictionary *savedStock = [[NSMutableDictionary alloc] initWithContentsOfFile:path];
    versionnum = @"";
    //it can be installed by user (for ex. it is 1.3 but first installed), no plist value is set before
    if(([savedStock objectForKey:@"versionnum"]) && (![[savedStock objectForKey:@"versionnum"] isEqualToString:@""])){
        versionnum = [savedStock objectForKey:@"versionnum"];
    }

    //to get the version of installed/updated-current app
    NSString *myversion = [NSString stringWithFormat:@"%@",[[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleVersion"]];
    //if no version has been set-first install- or my version is the latest version no need to do sth.
    if ([versionnum isEqualToString:myversion] || [versionnum isEqualToString:@""]) {
        NSLog(@"Nothing has to be done");
    }
    else {
        [self cleanDB];//i have clean tables and create my new db tables maybe logout the user etc.
        [savedStock setObject:[NSString stringWithString:myversion] forKey:@"versionnum"];//setting the new version
        [savedStock writeToFile:path atomically:YES];
    }
}