Question

我正在制作一个计算器应用程序，用于在按钮点击事件中创建一个对象。此计算器使用将运行总计存储为属性的对象，然后将新文本框中的新数字添加到该属性。 不幸的是每次点击按钮都会产生一个新对象，所以我没有一个恒定的运行总数。我试过if (object == null)但为了做到这一点，我必须将对象设置为null按钮事件因此它将始终为null。根据我的分配，必须在click事件中实例化对象。

public class Calculator
{
    public double Total  = 0.0;   // Running total for calculator

    public double Addition(double number)
    {
        Total += number;
        return Total;
    }

    public double Subtraction(double number)
    {
        Total -= number;
        return Total;
    }

    public double Multiplication(double number)
    {
        Total *= number;
        return Total;
    }

    public double Division(double number)
    {
        if (number != 0) // If number does not equal 0 Calculate
        {
            Total /= number;
            return Total;
        }
        Total = 0;      // If it does set the answer to 0 to avoid errors
        return Total;
    }

    public virtual void Clear()
    {
        Total = 0.0;
    }
}  

public class ScientificCalculator : Calculator
{
    public double Memory { get; set; } = 0.0;   // Running total for calculator

    public double Log(double number)
    {
        return Math.Log(number);
    }

    public double Sin(double number)
    {
        return Math.Sin(number);
    }

    public double Cos(double number)
    {
        return Math.Cos(number);
    }

    public double Tan(double number)
    {
        return Math.Tan(number);
    }

    public override void Clear()
    {
        Memory = 0.0;
    }
}

public partial class CalcQ3 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void btnAdd_Click(object sender, EventArgs e)
    {
        ScientificCalculator calc = null;
        bool isNumber = double.TryParse(txtNewNumber.Text, out double number);   // Testing if textbox value is numeric

        if (isNumber)                                                            // if numeric add number to total
        {
            if (calc == null)                                                    // if an instance has not been created creat one
            {
                calc = new ScientificCalculator();
            }

            calc.Addition(number);
            lblTotal.Text = (calc.Total).ToString();
        }
        else                                                                     // Display error
        {
            txtNewNumber.Text = string.Empty;
            txtNewNumber.Focus();
            lblTotal.Text = "Please Enter A Numeric Value";
        }
    }

    protected void btnClear_Click(object sender, EventArgs e)
    {
        ScientificCalculator calc = new ScientificCalculator();
        calc.Clear();
        lblTotal.Text = (calc.Total).ToString();
    }
}

Answer 1

很抱歉这个混乱。您只需要将calc作为静态

请参阅以下代码

map $status $limit {
    default '';
    401 $binary_remote_addr;
}

limit_req_zone $limit zone=api:10m rate=5r/s;


location /api {
    limit_req zone=api burst=5;
    ...
}

}

如何检查对象是否已在按钮处理程序中实例化

1 个答案: