objective-c - _NSCFConstantString latitude]：发送到实例的无法识别的选择器

Question

for(int i=0;i<[self.printers count]; i++)
    {
        PublicPrivateEvent *printerselection = [printers objectAtIndex:i];

        CGFloat latt = [printerselection.latitude floatValue]; //Here is broken
        CGFloat lng=[printerselection.longtitude floatValue];
         pointsCoOrds[index++] = CLLocationCoordinate2DMake(latt,lng);

    }

大家好，我试图从 PublicPrivateEvent 类中获取值。但我不知道我无法处理什么？我有这个问题：_NSCFConstantString latitude]: unrecognized selector sent to instance .. 你知道吗？提前致谢。