Question

我正在尝试学习iOS，我正在关注斯坦福大学视频，我试图重新创建一个计算器样本。但由于某种原因，=按钮不起作用或没有给出结果。我一步一步地按照练习，但根本不适合我。任何人都可以帮助我，我会非常感激。

//这是我的Calculator.h

#import <UIKit/UIKit.h>
#import "CalculatorBrain.h"

@interface ViewController : UIViewController {

    IBOutlet UILabel *display;
    CalculatorBrain *brain;
    BOOL userIsInTheMiddleOfTypingANumber;
}
-(IBAction) digitPressed:(UIButton *) sender;
-(IBAction) operationPressed: (UIButton *) sender;


@end
<code>





//This is my Calculator.m 

<pre>
#import "ViewController.h"
#import "CalculatorBrain.h"


@implementation ViewController

-(CalculatorBrain *) brain
    {
    if (!brain) brain = [[CalculatorBrain alloc] init];

        return brain;
     }
-(IBAction) digitPressed:(UIButton *) sender
    {
    NSString *digit = [[sender titleLabel]text];

    if (userIsInTheMiddleOfTypingANumber)
    {
        [display setText:[[display text] stringByAppendingString:digit]];

    }else{

        [display setText:digit];
        userIsInTheMiddleOfTypingANumber = YES;


    }
}

-(IBAction) operationPressed: (UIButton *) sender
  {

    if (userIsInTheMiddleOfTypingANumber)
  {
        [[self brain] setOperand:[[display text] doubleValue]];
        userIsInTheMiddleOfTypingANumber = NO;

  }
    NSString *operation = [[sender titleLabel] text];
    double result = [[self brain] performOperation:operation];
    [display setText:[NSString stringWithFormat:@"%g", result]];
  }

@end
<code>





//This is my CalculatorBrain.h

<pre>
#import <Foundation/Foundation.h>

@interface CalculatorBrain : NSObject {

    double operand;
    NSString *waitingOperation;
    double waitingOperand;


}
-(void)setOperand:(double)anOperand;
-(double)performOperation:(NSString *) operation;

@end
<code>





//This is my CalculatorBrain.m
<pre>
#import "CalculatorBrain.h"

@implementation CalculatorBrain

-(void)setOperand:(double)anOperand{

    operand = anOperand;

}
-(void) performWaitingOperation{

    if ([@"+" isEqual:waitingOperation])
    {
        operand = waitingOperand + operand;
    }
    else if ([@"*" isEqual:waitingOperation])
    {
        operand = waitingOperand - operand;
    }
    else if ([@"-" isEqual:waitingOperation])
    {
        operand = waitingOperand * operand;
    }
    else if([@"/" isEqual:waitingOperation])
    {

        if (operand)
        {
            operand = waitingOperand / operand;


      }
   }

}
-(double)performOperation:(NSString *) operation
{

    if ([operation isEqual:@"sqrt"])
    {
        operand = sqrt(operand);
    }
    else if([@"*+/-=" isEqual:operation])
    {
        [self performWaitingOperation];
        waitingOperation = operation;
        waitingOperand = operand;

 }
return operand;

}

@end
<code>

Answer 1

除了if（[@“* + / - =”isEqual：operation]）catch之外，还有另外一个问题：

if ([@"*" isEqual:waitingOperation])
    {
        operand = waitingOperand - operand;
    }
    else if ([@"-" isEqual:waitingOperation])
    {
        operand = waitingOperand * operand;
    }

逻辑错误。

接下来将performWaitingOperation函数更改为

-(double) performWaitingOperation{

    if ([@"+" isEqual:waitingOperation])
    {
        return operand = waitingOperand + operand;
    }
    else if ([@"*" isEqual:waitingOperation])
    {
        return operand = waitingOperand * operand;
    }
    else if ([@"-" isEqual:waitingOperation])
    {
        return operand = waitingOperand - operand;
    }
    else if([@"/" isEqual:waitingOperation])
    {

        if (operand)
        {
            return operand = waitingOperand / operand;


      }
   }else if ([@"=" isEqual:waitingOperation]){
        return operand;
     }

}

并更改[self performWaitingOperation]; to operand = [self performWaitingOperation];

好的首发：Calculator tutorial

希望这会有所帮助..

Answer 2

我认为这是这一行。 if（[@“ + / - =”isEqual：operation]）。除非你的字符串'operation'字面上是字符串“ + / - =”，否则永远不会评估为true。你可能想要，instad，分别与每个thos进行比较。例如if（[@“*”isEqual：operation] || [@“+”isEqual：operation] ... etc

Answer 3

如果您有任何问题，请参阅以下link 它一起为您提供计算器大脑项目。

iOS中的计算器示例：=符号未响应我的代码

3 个答案: