Objective-C二进制表达式的操作数无效

Question

我收到错误:

二进制表达式的无效操作数('UITextField')

我的.h看起来像这样:

@interface ViewController : UIViewController{

    IBOutlet UILabel *resultLabel;
    float result;
    IBOutlet UITextField *miles;
    IBOutlet UITextField *mpgLoaded;
    IBOutlet UITextField *mpgEmpty;
    IBOutlet UITextField *fuelCost;
    IBOutlet UITextField *payment;
}

-(IBAction)result:(id)sender;

-(IBAction)reset:(id)sender;


@end

错误来自我想在.m中进行的计算:

-(IBAction)result:(id)sender{
    result = payment - ((miles/mpgLoaded)*fuelCost)-((miles/mpgEmpty)*fuelCost);
    resultLabel.text = [NSString stringWithFormat:@"%.2f",result];
}

Answer 1

您需要询问每个UITextField值的值(即text属性),并将每个值从字符串转换为float.例如

result = payment.text.floatValue - ((miles.text.floatValue / ...