离开方法时如何保存变量值？

Posted 2023-05-07

【中文标题】离开方法时如何保存变量值？

【英文标题】：How to save a variables value when leaving the method?

【发布时间】：2017-05-27 09:52:43

【问题描述】：

我有一个方法可以计算用户从 atm 取款的次数（因为有限制），还可以计算用户当天取款的金额。但是，count var 和 amountWithdrawn 变量中的值在离开方法时都丢失了，我如何让它们“保存”？ 另外作为旁注，我有一个名为Account 的类，它有余额等，最好把它们放在那里吗？但也想知道是否可以将变量保存在方法中以供将来参考。

public decimal WithDraw()

    int timesWithdrawn = 9;

    decimal amountWithdrawnToday = 0;
    decimal money = 0;
    bool success = false;
    if (timesWithdrawn < 10)
    
        do
        
            //Console.WriteLine("0 available to withdraw.", FundsAvailable);
            Console.WriteLine("How much would you like to withdraw?");
            try
            
                money = decimal.Parse(Console.ReadLine());
                if (money % 5 == 0 && money <= account.CurrentBalance && money <= 1000)
                
                    success = true;
                
                if (money == 0)
                
                    bool exit = true;
                    Console.WriteLine("Do you want to exit? Type \"yes\", or \"no\".");
                    while (exit == true)
                    
                        string response = Console.ReadLine();
                        if (response.ToLower() == "yes")
                        
                            break;
                        
                        else
                        
                            exit = false;
                        
                    
                
            
            catch (FormatException)
            
                Console.WriteLine("Please enter a number to withdraw.");
            
         while (success == false);
        //do while this is true
        Console.WriteLine(account.CurrentBalance);
        Console.WriteLine("Withdrawing 0 pounds.", money);
        Console.WriteLine("You have 0 remaining in your account.", account.CurrentBalance - money);
        amountWithdrawnToday += money;
        timesWithdrawn += 1;
        Console.WriteLine("0 pounds withdrawn today", amountWithdrawnToday);
        return account.CurrentBalance -= money;
    
    else
    
        Console.WriteLine("You have exceeded daily withdrawls. You have withdrawn 0", amountWithdrawnToday);
        return amountWithdrawnToday;
    

【问题讨论】：

在我看来，对于这种特定用途，最好使用帐户类，因为它包含有关帐户的信息。此外，可以创建一个“包装器”类，从包含方法外所需的所有信息的方法返回。另一种选择是使用 out 或 ref 参数。发送参数会在发送它们的上下文中更改它们。你可以在这里阅读更多关于它的信息link

【参考方案1】：

我建议你需要将这些变量放在Account 类中，我也建议你可以将withdraw 方法本身放在Account 类中，这样可能对OOP 更友好。

要保存timesWithdrawn 编号，您只需将其设为类实例可变，而不是将其设为局部变量

这里是代码

class Account

    public decimal CurrentBalance  get; set; 
    public int timesWithdrawn  get; set;  = 9;

    public decimal WithDraw()
    
        decimal amountWithdrawnToday = 0;
        decimal money = 0;
        bool success = false;
        if (timesWithdrawn < 10)
        
            do
            
                //Console.WriteLine("0 available to withdraw.", FundsAvailable);
                Console.WriteLine("How much would you like to withdraw?");
                try
                
                    money = decimal.Parse(Console.ReadLine());
                    if (money % 5 == 0 && money <= CurrentBalance && money <= 1000)
                    
                        success = true;
                    
                    if (money == 0)
                    
                        bool exit = true;
                        Console.WriteLine("Do you want to exit? Type \"yes\", or \"no\".");
                        while (exit == true)
                        
                            string response = Console.ReadLine();
                            if (response.ToLower() == "yes")
                            
                                break;
                            
                            else
                            
                                exit = false;
                            
                        
                    
                
                catch (FormatException)
                
                    Console.WriteLine("Please enter a number to withdraw.");
                
             while (success == false);
            //do while this is true
            Console.WriteLine(CurrentBalance);
            Console.WriteLine("Withdrawing 0 pounds.", money);
            Console.WriteLine("You have 0 remaining in your account.", CurrentBalance - money);
            amountWithdrawnToday += money;
            timesWithdrawn += 1;
            Console.WriteLine("0 pounds withdrawn today", amountWithdrawnToday);
            return CurrentBalance -= money;
        
        else
        
            Console.WriteLine("You have exceeded daily withdrawls. You have withdrawn 0", amountWithdrawnToday);
            return amountWithdrawnToday;
        
    

正如您从代码中注意到的那样，我删除了对 account 变量的引用，并将 CurrentBalance 设为 实例变量 以及 timesWithdrawn。

即使在方法完成后，这也可以保留timesWithdrawn 的值。

【参考方案2】：

只要程序正在运行，它就会保存在那里，但是一旦它完全重置，所以是的，你必须将它保存在数据库中的某个地方，一个 Excel 表格或一个文本文档中 Saving data to a file in C#

如果你需要一些帮助来做这样的事情，看看这个

【讨论】：

虽然你是对的，但操作员没有问这个问题，操作员在完成激发它后询问从方法中获取值

【参考方案3】：

您可以将“out”参数传递给函数，它基本上是您发送给函数的变量，它在函数外部保存其值。 例如：

public void WithDraw(out int c) 
    c = something ; //c must receive a value during the call
  

int myvar; // the parameter which will hold the value when the function returns

WithDraw(out myvar);  //call to the function

myvar  //will now hold a value from the function (something)

您还可以考虑返回一个元组，或者将您希望保存的值放入“全局变量”中。