ios - 如何在 Objective-C 中将字符串插入到 sqlite？

Question

我无法将 NSMutableString 插入到 sqlite。 我从网络服务器成功获取信息并成功创建了 sqlite 文件，但我无法将数据从网络插入到 sqlite。

我觉得问题就出在这里

NSString *insertSQL = @"INSERT INTO Questions VALUES (result)";

但我不确定，我无法解决这个问题。谁能帮帮我？

- (void)getInforamtionFromWeb {
    NSURL *url = [NSURL URLWithString:kGetUrl];
    data = [NSData dataWithContentsOfURL:url];
    NSError *error;
    json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
    result = [[NSMutableString alloc] init];
    for (NSObject * obj in json)
    {
        [result appendString:[obj description]];
    }
}

-(void)initiatSqlite{
    // Get the documents directory
    dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    docsDir = dirPaths[0];
    // Build the path to the database file
    _databasePath = [[NSString alloc]
                     initWithString: [docsDir stringByAppendingPathComponent:
                                      @"Questions.db"]];
    NSFileManager *filemgr = [NSFileManager defaultManager];
    if ([filemgr fileExistsAtPath: _databasePath ] == NO)
    {
        const char *dbpath = [_databasePath UTF8String];
        if (sqlite3_open(dbpath, &_contactDB) == SQLITE_OK)
        {
            char *errMsg;
            const char *sql_stmt =
            "CREATE TABLE IF NOT EXISTS Questions (ID INTEGER PRIMARY KEY AUTOINCREMENT, Question Text, AnswerA Text, AnswerB Text, AnswerC Text, AnswerD Text, CorrectAnswer Text, Explanation Text)";
            if (sqlite3_exec(_contactDB, sql_stmt, NULL, NULL, &errMsg) != SQLITE_OK)
            {
                [self Worningtitle:@"Error" Message:@"Failed to create table"];
            }
            sqlite3_close(_contactDB);
        } else {
            [self Worningtitle:@"Error" Message:@"Failed to open/create database"];

        }
    }

}
- (void) insertData
{
    sqlite3_stmt    *statement;
    const char *dbpath = [_databasePath UTF8String];


    if (sqlite3_open(dbpath, &_contactDB) == SQLITE_OK)
    {
        NSString *insertSQL = @"INSERT INTO Questions VALUES (result)";

        const char *insert_stmt = [insertSQL UTF8String];
        NSLog(@"%s",insert_stmt);
        sqlite3_prepare_v2(_contactDB, insert_stmt, -1, &statement, NULL);
        sqlite3_bind_text(statement, 1, [result UTF8String], -1, SQLITE_TRANSIENT);

        if (sqlite3_step(statement) == SQLITE_DONE)
        {
            NSLog(@"Product added");
        } else {
            NSLog(@"Failed to add Product");
        }

        sqlite3_finalize(statement);
        sqlite3_close(_contactDB);
    }
}

Answer 1

你是对的。您的 INSERT 语句不正确。它必须是:

NSString *insertSQL = @"INSERT INTO Questions VALUES (?)";

? 是应用 sqlite3_bind_xxx 的地方。

请记住，您的 Questions 表有很多列，但您只插入了一个值。您应该指定应将值插入到哪一列。示例:

NSString *insertSQL = @"INSERT INTO Questions (Question) VALUES (?)";

将 Question 替换为您的 result 值应放入的正确列名。

顺便说一句 - 您的代码需要做更多的工作才能变得更好。您需要添加更多的错误检查，尤其是 sqlite3_prepare_v2。

基于想要插入更多数据，你会做这样的事情:

- (BOOL)insertData {
    BOOL result = NO; // failed
    const char *dbpath = [_databasePath UTF8String];
    if (sqlite3_open(dbpath, &_contactDB) == SQLITE_OK) {
        const char *insert_stmt = "INSERT INTO Questions(AnswerA,AnswerB,AnswerC,AnswerD,CorrectAnswer,Question) VALUES (?,?,?,?,?,?)";
        sqlite3_stmt *statement;

        if (sqlite3_prepare_v2(_contactDB, insert_stmt, -1, &statement, NULL) == SQLITE_OK) {
            sqlite3_bind_text(statement, 1, [answerA UTF8String], -1, SQLITE_TRANSIENT);
            sqlite3_bind_text(statement, 2, [answerB UTF8String], -1, SQLITE_TRANSIENT);
            sqlite3_bind_text(statement, 3, [answerC UTF8String], -1, SQLITE_TRANSIENT);
            sqlite3_bind_text(statement, 4, [answerD UTF8String], -1, SQLITE_TRANSIENT);
            sqlite3_bind_text(statement, 5, [correctAnswer UTF8String], -1, SQLITE_TRANSIENT);
            sqlite3_bind_text(statement, 6, [question UTF8String], -1, SQLITE_TRANSIENT);

            if (sqlite3_step(statement) == SQLITE_DONE) {
                NSLog(@"Product added");
                result = YES;
            } else {
                NSLog(@"Failed to add Product: %s", sqlite3_errmsg(_contactDB));
            }

            sqlite3_finalize(statement);
        } else {
            NSLog(@"Unable to prepare statement: %s", sqlite3_errmsg(_contactDB);
        }

        sqlite3_close(_contactDB);
    } else {
        NSLog(@"Unable to open database: %@", sqlite3_errmsg(_contactDB));
    }

    return result;
}

请注意，您需要使用对包含每列数据的实际变量/值的引用来更新每个 sqlite3_bind_text 调用。

您也不需要为 ID 绑定(bind)值，因为它已设置为自动填充。

注意所有正确的错误检查。我也这样做了 insertData 返回一个 BOOL 指示数据是否已成功添加。