ios - 无法使用连续输入实现减法功能。无法在计算器应用程序中找到合适的逻辑来实现

Question

加法正常工作，但减法变为负数。我尝试了不同的可能逻辑，但找不到合适的逻辑。前两个输入以及减号按钮提供了正确的解决方案。当与第三个输入一起使用减法时，此解决方案不会按应有的方式发生。有 0-9 个按钮可以输入数字。一个加号按钮触发以下方法 -(IBAction)adding:(id)sender; ，一个减号按钮触发此方法。 -(IBAction)subtract:(id)sender; 一个用于触发主要功能的等号按钮 -(IBAction)equals:(id)sender; 将被添加到减法和主要等号方法下面是函数实现的代码，即.m文件。

int eq;

@implementation ViewController

@synthesize temp = _temp;
@synthesize inputField = _inputField;
@synthesize outputField = _outputField;

-(IBAction)adding:(id)sender
{
  self.temp = self.input + self.output;
  self.input = 0;
  eq = 0;

}

-(IBAction)subtract:(id)sender
{
  self.temp = self.input - self.output;
  self.input = 0;
  eq = 1;
}

-(IBAction)digits:(id)sender
{
  UIButton *b = (UIButton *)sender;
  self.input = self.input * 10 + b.tag;
  [self showInput];
}

-(IBAction)clear:(id)sender
{
  self.input = 0;
  [self showInput];
  self.output = 0;
  [self showOutput];
}

-(IBAction)clearE:(id)sender
{
  self.input = self.input * 0.1;
  [self showInput];
}

-(IBAction)equals:(id)sender
{
  if (eq == 0) {
    self.output = self.temp + self.input;
    self.temp = 3;
  }
  if (eq ==1)
  {
    self.output = self.temp - self.input;
    self.temp = 3;
  }
  [self showOutput];
  self.input = 0;
  [self showInput];
}

-(void)showInput
{
  self.inputField.text = [NSString stringWithFormat:@"%lld", self.input];
}

-(void)showOutput
{
  self.outputField.text = [NSString stringWithFormat:@"%lld", self.output];
}

- (void)viewDidLoad
{
  [super viewDidLoad];
  self.inputField.text = [NSString stringWithFormat:@"%lld",self.input];
  self.outputField.text= [NSString stringWithFormat:@"%lld", self.output];
}

- (void)didReceiveMemoryWarning
{
  [super didReceiveMemoryWarning];
  // Dispose of any resources that can be recreated.
}

@end

.h文件是这样的：

@interface ViewController : UIViewController

@property (nonatomic,readwrite,weak) IBOutlet UILabel *inputField;
@property (assign,readwrite,) unsigned long long input;
@property(assign,readwrite) unsigned long long temp;
@property (nonatomic,readwrite,weak) IBOutlet UILabel *outputField;
@property (assign,readwrite) unsigned long long output;

-(IBAction)digits:(id)sender;
-(IBAction)adding:(id)sender;
-(IBAction)subtract:(id)sender;
-(IBAction)clear:(id)sender;
-(IBAction)clearE:(id)sender;
-(IBAction)equals:(id)sender;
@end