Question

我创建了一个简单的计算器。一切都很好;但是，如果我除以零，我想显示一条错误消息。我知道如何做警报弹出窗口，但我不知道如何实现它，所以它在我除以零时出现。这是我的计算器代码：

- (IBAction)buttonOperationPressed:(id)sender {
    if (currentOperation == 0) result = currentNumber;
    else {
        switch (currentOperation) {
            case 1:
                result = result + currentNumber;
                break;
            case 2:
                result = result - currentNumber;
                break;
            case 3:
                result = result * currentNumber;
                break;
            case 4:
                result = result / currentNumber;
                break;
            case 5:
                currentOperation = 0;
                break;
            default:
                break;
        }
    }
    currentNumber = 0;
    CalcDisplay.text = [NSString stringWithFormat:@"%g",result];
    if ([sender tag] == 0) result = 0;
    currentOperation = [sender  tag];
    userInTheMiddleOfEnteringDecimal = NO;

Answer 1

您可以在进行分割之前添加测试，例如改变：

        case 4:
            result = result / currentNumber;
            break;

为：

        case 4:
            if (currentNumber == 0)
                // ... do alert here ...
            else
                result = result / currentNumber;
            break;

Answer 2

- (IBAction)buttonOperationPressed:(id)sender {
if (currentOperation == 0) result = currentNumber;
else {
    switch (currentOperation) {
       case 1:
            result = result + currentNumber;
            break;
        case 2:
            result = result - currentNumber;
            break;
        case 3:
            result = result * currentNumber;
            break;
        case 4:
            if(currentNumber == 0){
                UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Title" message:@"Message" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
[alert show];
            }else{

                result = result / currentNumber;

            }

            break;
        case 5:
            currentOperation = 0;
            break;
        default:
            break;
    }
}
currentNumber = 0;
CalcDisplay.text = [NSString stringWithFormat:@"%g",result];
if ([sender tag] == 0) result = 0;
currentOperation = [sender  tag];
userInTheMiddleOfEnteringDecimal = NO;

请尝试使用此代码，我已复制粘贴您提供的代码并添加了一些必要的代码，我认为这些代码可以解决您的问题。

Answer 3

您必须检查第二个分区操作数是否为零，如果是，则打印错误消息。不要忘记，你不能只将double或某些东西与==进行比较，你必须使用预设，如下所示：

case 4:
    if(ABS(currentNumber) < 1e-12) // most probably its zero
        // your message
        return;

计算器除以零

3 个答案: