objective-c - [NSMutableArray objectAtIndex :]: index 0 beyond bounds for empty array'

Question

我收到此错误:[NSMutableArray objectAtIndex:]: index 0 beyond bounds for empty array 尽管我的数据库中有 75 个项目。为什么它向我显示此错误？我试图从我的数据库中获取项目，但它告诉我索引为 0。

+(NSMutableArray *)GetAttitudeItems
{
    NSArray *arrDocPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *strDestPath = [NSString stringWithFormat:@"%@/ItemsAndCategory.sqlite",[arrDocPath objectAtIndex:0]];


//sqlite3 *sqlite;

NSMutableArray *arrItemsList;
if(sqlite3_open([strDestPath UTF8String],&database)==SQLITE_OK)
{

    const char *strQuery = "SELECT * FROM Items WHERE CategoryName='ATTITUDE' ORDER BY RANDOM()";
    NSLog(@"The value is %s",strQuery);
    sqlite3_stmt *stmt;
    //char *err;

    arrItemsList  = [[NSMutableArray alloc]init];

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

            NSString *StrCatename = [NSString stringWithUTF8String:(char*)sqlite3_column_text(stmt, 1)];
            NSString *StrItemName = [NSString stringWithUTF8String:(char*)sqlite3_column_text(stmt, 0)];

            Itemslist *itemlist = [[Itemslist alloc]init];
            itemlist.CategoryValue = StrCatename;
            itemlist.ItemValue =StrItemName;
            [arrItemsList addObject:itemlist];

        }

    }

    if (stmt!=nil)
    {
        sqlite3_finalize(stmt);
    }
}



sqlite3_close(database);

return arrItemsList;

Answer 1

如果您确信您的数据库调用应该返回数据，我将确保您的 if () else () 语句中至少有一个确实被命中。否则，鉴于您在上面对其进行了初始化，您的数组为空:

NSMutableArray *arrAlert = [[NSMutableArray alloc]init];

一个简单的 self 检查方法是在 if else 链的底部添加一个 else 语句，并断言一些东西那里(即至少打印一些东西，对于初学者来说。)