ios - 尝试建立 SQLite 连接/语句时应用程序崩溃

Question

我在使用 SQLite 时遇到问题，当我尝试连接到 SQLite 数据库并获取其部分内容时，我的应用程序在运行时崩溃。这是我的代码:

-(IBAction)setInput:(id)sender
{
    NSString *strStoreNumber;
    NSString *strRegNumber;

    strStoreNumber = StoreNumber.text;
    strRegNumber = RegNumber.text;
    lblStoreNumber.text = strStoreNumber;
    lblRegNumber.text = strRegNumber;

    NSString* databasePath = [[NSBundle mainBundle] pathForResource:@"tblStore" ofType:@"sqlite"];

    if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) 
    {
        NSLog(@"Opened sqlite database at %@", databasePath);
        //...stuff
    } 
    else 
    {
        NSLog(@"Failed to open database at %@ with error %s", databasePath, sqlite3_errmsg(database));
        sqlite3_close (database);
    }

    NSString *querystring;

    querystring = [NSString stringWithFormat:@"SELECT strStore FROM tblStore WHERE strStore = %@;", strStoreNumber];  

    const char *sql = [querystring UTF8String];

    NSString *szStore = nil;
    NSString *szReg = nil;

    sqlite3_stmt *statement = nil;
    if (sqlite3_prepare_v2(database, sql, -1, &statement, NULL)!=SQLITE_OK) //queryString = Statement
    {
        NSLog(@"sql problem occured with: %s", sql);
        NSLog(@"%s", sqlite3_errmsg(database));
    }
    else
    {
        // you could handle multiple rows here
        while (sqlite3_step(statement) == SQLITE_ROW) // queryString = statement
        {            
            szStore = [NSString stringWithUTF8String:(char*)sqlite3_column_text(statement, 0)];
            szReg = [NSString stringWithUTF8String:(char*)sqlite3_column_text(statement, 1)];
        } // while        

    }

    sqlite3_finalize(statement);    
    // go on with putting data where you want    
} 

我在控制台中遇到的错误:

2012-05-07 09:39:33.619 CCoDBTry[962:f803] Opened sqlite database at /Users/*******/Library/Application Support/iPhone Simulator/5.1/Applications/5DB7A218-A0F6-485F-B366-91FD2F9BC062/CCoDBTry.app/tblStore.sqlite
2012-05-07 09:39:33.623 CCoDBTry[962:f803] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** +[NSString stringWithUTF8String:]: NULL cString'
*** First throw call stack:
(0x1593022 0x1724cd6 0x153ba48 0x153b9b9 0x9d4973 0x27c9 0x1594e99 0xd714e 0xd70e6 0x17dade 0x17dfa7 0x17d266 0xfc3c0 0xfc5e6 0xe2dc4 0xd6634 0x147def5 0x1567195 0x14cbff2 0x14ca8da 0x14c9d84 0x14c9c9b 0x147c7d8 0x147c88a 0xd4626 0x1f82 0x1ef5)
terminate called throwing an exception(lldb)

非常感谢任何帮助!

编辑:注意我在数据库中寻找的值是 VARCHAR 类型。我不确定知道这是否有所作为。

Answer 1

+[NSString stringWithUTF8String:]: NULL cString

它提示您向 stringWithUTF8String: 中输入了空值。您的代码对该方法有两次调用，每次都从查询结果中输入一个值。查看您的查询，您只选择了一个列 strStore。我假设分配给 szReg 的行失败了，因为您正在尝试检索您未在查询中选择的值。