ios - sqlite 中的更新行未更新

Question

我试图只更新一行中的一个单元格，但无法使其工作。更新方法:

- (void) UpdateQuestionShownParameter:(int)QuestionId :(BOOL)QuestionShown{
    @try {
        NSFileManager *fileMgr = [NSFileManager defaultManager];
        NSString *dbPath = [[[NSBundle mainBundle] resourcePath ]stringByAppendingPathComponent:@"Milionar.sqlite"];
        const char *sql = "UPDATE Questions set Show = ? WHERE id = ?";


        BOOL success = [fileMgr fileExistsAtPath:dbPath];
        if(!success)
        {
            NSLog(@"Cannot locate database file '%@'.", dbPath);
        }
        if(sqlite3_open([dbPath UTF8String], &db) == SQLITE_OK)
        {
            sqlite3_stmt *sqlStatement;
            if(sqlite3_prepare_v2(db, sql, -1, &sqlStatement, NULL) == SQLITE_OK)
            {
                NSInteger shownInteger = (QuestionShown ? 1 : 0);

                sqlite3_bind_int(sqlStatement, 1, shownInteger);
                sqlite3_bind_int(sqlStatement, 2, QuestionId);

                if (sqlite3_step(sqlStatement) != SQLITE_DONE)
                {
                    NSLog(@"Error while updating. '%s'", sqlite3_errmsg(db));
                }
                sqlite3_finalize(sqlStatement);

            }
            else
            {
                NSLog(@"Problem with prepare statement");
            }
        }
        else
        {
            NSLog(@"An error has occured while opening database.");
        }

        sqlite3_close(db);

    }
    @catch (NSException *exception) {
        NSLog(@"An exception occured: %@", [exception reason]);
    }
}

在 ViewDidLoad 中尝试:

- (void)viewDidLoad
{
    ListOfQuestions *listQuestions =[[ListOfQuestions alloc] init];
    self.Questions = [listQuestions getQuestions];
    Question *generatedQuestion = (Question *) [self.Questions objectAtIndex:0];
    [listQuestions UpdateQuestionShownParameter:generatedQuestion.id :TRUE];
    [self.Description setText:(generatedQuestion.Description)];

    [super viewDidLoad];
    // Do any additional setup after loading the view.
}

每次我尝试运行应用程序时，我都会在显示列中得到 0。但我没有任何错误。那么我是否做错了什么，或者每次当我尝试在模拟器中运行应用程序时，我都会从项目数据库重新创建数据库？谢谢

Answer 1

您正在打开 bundle 中的数据库，该数据库是只读的。如果文档文件夹中尚不存在该数据库，您应该将数据库从 bundle 复制到文档文件夹:

NSString *filename         = @"Milionar.sqlite";
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *bundlePath       = [[[NSBundle mainBundle] resourcePath ]stringByAppendingPathComponent:filename];
NSString *documentsFolder  = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
NSString *documentsPath    = [documentsFolder stringByAppendingPathComponent:filename];

if (![fileManager fileExistsAtPath:documentsPath]) {
    NSError *error = nil;
    BOOL success = [fileManager copyItemAtPath:bundlePath toPath:documentsPath error:&error];
    NSAssert(success, @"Unable to copy database: %@", error);
}

if (sqlite3_open([documentsPath UTF8String], &db) != SQLITE_OK) {
    NSLog(@"Open failed");
} else {
    // ...
}

有关文档所属位置的更多信息，请参阅 File System Programming Guide .

<小时/>

顺便说一句，如果您正在寻找模拟器的 Documents 文件夹，该文件夹位于 ~/Library/Application Support/iPhone Simulator 中(在 Xcode 6 中，现在是 ~/Library/Developer/CoreSimulator/Devices)。如果您没有看到“Library”文件夹，可以通过在终端命令行界面中键入以下命令来取消隐藏它:

chflags nohidden ~/Library