ios - 计算器除以零

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，所以当我除以零时它会出现。这是我的计算器代码的片段:

- (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

您可以在除法之前添加一个测试，例如改变:

        case 4:
            result = result / currentNumber;
            break;

到:

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