如何解决运行时错误NSString,sqlite3_column_text NULL问题？

Question

我是iphone应用程序开发人员的新手,我正在使用sqlite3数据库,在应用程序委托中,我正在跟踪代码并运行正常我们也在数据库中找到了值,在我的应用程序中,

但是,应用程序会立即讨论为什么会发生这种情况我不明白.

代码如下

        -(void)Data
      {
   databaseName = @"dataa.sqlite";

        NSArray *documentPaths =   NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
      NSString *documentsDir = [documentPaths objectAtIndex:0];
     databasePath =[documentsDir stringByAppendingPathComponent:databaseName];

    [self checkAndCreateDatabase];

    list1 = [[NSMutableArray alloc] init];  

    sqlite3 *database;
    if (sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK)
    {
       if(detailStmt == nil)
        {
                    const char *sql = "Select * from Dataa";            
             if(sqlite3_prepare_v2(database, sql, -1, &detailStmt, NULL) ==    SQLITE_OK)
            {               
                    //NSLog(@"Hiiiiiii");
                //sqlite3_bind_text(detailStmt, 1, [t1 UTF8String], -1,    SQLITE_TRANSIENT);
                //sqlite3_bind_text(detailStmt, 2, [t2 UTF8String], -2, SQLITE_TRANSIENT);
                  //sqlite3_bind_int(detailStmt, 3, t3);

                   while(sqlite3_step(detailStmt) == SQLITE_ROW) 
                 {
                    //NSLog(@"Helllloooooo");




                     NSString *item= [NSString stringWithUTF8String:(char *)sqlite3_column_text(detailStmt, 0)];
                //NSString *fame= [NSString stringWithUTF8String:(char *)sqlite3_column_text(detailStmt, 1)];
                //NSString *cinemax = [NSString stringWithUTF8String:(char *)sqlite3_column_text(detailStmt, 2)];
                //NSString *big= [NSString stringWithUTF8String:(char *)sqlite3_column_text(detailStmt, 3)];

                //pvr1 = pvr;
                item1=item;
                //NSLog(@"%@",item1);

                data = [[NSMutableArray alloc] init];   


                list *animal=[[list alloc] initWithName:item1];

                // Add the animal object to the animals Array
                [list1 addObject:animal];
                //[list1 addObject:item];


            }
            sqlite3_reset(detailStmt);
        }
        sqlite3_finalize(detailStmt);
        //  sqlite3_clear_bindings(detailStmt);
    }
}
detailStmt = nil;
sqlite3_close(database);

}

当我们看到控制台时,他们会显示以下错误

    2010-03-09 10:02:40.262 SanjeevKapoor[430:20b] *** Terminating app due to uncaught     exception 'NSInvalidArgumentException', reason: '*** +[NSString stringWithUTF8String:]:    NULL cString'

当我们看到调试器时,它们会在下一行中显示错误

          NSString *item= [NSString stringWithUTF8String:(char *)sqlite3_column_text(detailStmt, 0)];

我无法解决那个问题,请帮助我.

Answer 1

你可以用NSString stringWithFormat:@"%s".这也优雅地处理NULL价值观.

Answer 2

Sqlite可以存储NULL对象,这些对象与空字符串不同.在您的情况下,您从base中提取了值,结果为NULL.但[NSString stringWithUTF8String:]方法不能使用NULL作为参数,因此会引发错误.你应该检查提取的值:

char * str = (char*)sqlite3_column_text(statement, i);
if (str){
    item = [NSString stringWithUTF8String:str];
}
else{
    // handle case when object is NULL, for example set result to empty string:  
    item = @"";
}