如何在 ios 6 上打开 sqlite 数据库？

Question

我是 ios 开发的新手。我现在尝试做的是打开一个现有的 sqlite 数据库并从中选择数据。我调试了我的源代码，发现我打开了数据库成功（我认为我成功了，因为 *database 指针不为零）。但是当我使用 sqlite3_prepare_v2() 来初始化选择查询时，我总是收到错误：“没有这样的表 People”。我已经检查了路径：

~/Library/Application Support/iphone模拟器/6.0/Application//.

数据库复制成功，可以打开看看里面的数据。

这是我复制数据库并打开它的代码：

- (NSString*) getDatabasePath{
    //Search for standard documents using NSSearchPathForDirectoriesInDomains
    //First Param = Searching the documents directory
    //Second Param = Searching the Users directory and not the System
    //Expand any tildes and identify home directories.
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory , NSUserDomainMask, YES);
    NSString *documentsDir = [paths objectAtIndex:0];
    return [documentsDir stringByAppendingPathComponent:@"data.sqlite"];
}

- (void)copyDatabaseToDocument {
    //Using NSFileManager we can perform many file system operations.
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSError *error;
    NSString *dbPath = [self getDatabasePath];
    BOOL success = [fileManager fileExistsAtPath:dbPath];

    if(!success) {

        NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"data.sqlite"];
        success = [fileManager copyItemAtPath:defaultDBPath toPath:dbPath error:&error];

        if (!success)
            NSAssert1(0, @"Failed to create writable database file with message '%@'.", [error localizedDescription]);
    }
}

- (sqlite3*)openDatabaseConnection {
    sqlite3 *database;
    NSString * path = [self getDatabasePath];

    if (sqlite3_open([path UTF8String], &database) != SQLITE_OK) {
        sqlite3_close(database);
        NSAssert1(0, @"Failed to open database with message '%s'.", sqlite3_errmsg(database));
    }
    return database;
}

这是我选择数据的代码。错误发生在以下行：sqlite3_prepare_v2(database, query, -1, &selectStatement, NULL)

- (People*) getPeople{
    sqlite3 *database = [[[DBConnector alloc] init] openDatabaseConnection];
    if(database == nil)
        return nil;
    sqlite3_stmt *selectStatement;
    NSString *rawquery      = @"select * from people";
    const char *query       = [rawquery UTF8String];
    NSMutableArray* result = [[NSMutableArray alloc] init];

    if (sqlite3_prepare_v2(database, query, -1, &selectStatement, NULL) == SQLITE_OK) {
        while (sqlite3_step(selectStatement) == SQLITE_ROW) {

            //Parse the data by calling a private method:
            People *people = [self parsePeopleWithStatement:selectStatement];

            [result addObject:people];
        }
    }else{
        NSAssert1(0, @"Error: '%s'.", sqlite3_errmsg(database));
    }
    sqlite3_finalize(selectStatement);
    return result;

}

如果您知道我犯了什么错误，请告诉我。

谢谢。

Answer 1

我自己解决了这个问题。当我调试应用程序时，我看到它没有调用applicationDidFinishLaunching 方法，它调用了applicationDidFinishLaunchingWithOptions 方法。我只是将代码放在applicationDidFinishLaunchingWithOptions 方法中调用copyDatabaseToDocument 并且它可以工作。 这是我的 Delegate 类的代码：

//THIS METHOD WAS NOT CALLED
- (void)applicationDidFinishLaunching:(UIApplication *)application{
    DBConnector *connector = [[DBConnector alloc] init];
    [connector copyDatabaseToDocument];
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
       self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

       //SHOW MY SCREEN
        (...)

       self.window.backgroundColor = [UIColor whiteColor];
       [self.window makeKeyAndVisible];
       return YES;
}

顺便说一句，我认为这不是真正的答案同步我不知道为什么我的应用程序没有在 applicationDidFinishLaunching() 处启动。如果你知道，请给我一个描述。

谢谢。