Question

如果我有一系列这样的if / else语句，我想得到一个特定的值，那么我如何在等式之外访问该值？我让所有内容都通过命令提示符，并且没有其他任何课程。

if (shippingInput == 1)
{
    double shippingAmount = shippingDetails * 3;
}
else if (shippingInput == 2)
{
    double shippingAmount = shippingDetails * 4;
}
else
{
    double shippingAmount = shippingDetails * 5.5;
}

我的代码即将结束

double shippingCost = shippingAmount + surcharge;

但是它的名字是＆＃39; shippingAmount＆＃39;和＆＃39;附加费＆＃39;在当前上下文中不存在。

感谢您的帮助！我还没有标记答案，但是在if / else括号之外声明语句并从每个语句中删除双重语句后，它完美地运行了。

Answer 1

每次都在制作新的变量。像这样宣布一次：

double shippingAmount;

if (shippingInput == 1)
{
    shippingAmount = shippingDetails * 3;
}
else if (shippingInput == 2)
{
    shippingAmount = shippingDetails * 4;
}
else
{
    shippingAmount = shippingDetails * 5.5;
}

Answer 2

你需要在语句之外定义变量。

double shippingAmount;


/*some more logic*/

if (shippingInput == 1)
{
    shippingAmount = shippingDetails * 3;
}
else if (shippingInput == 2)
{
    shippingAmount = shippingDetails * 4;
}
else
{
    shippingAmount = shippingDetails * 5.5;
}

通过在if / else语句中定义变量，它们只存在于大括号上下文中，因此一旦您退出代码块，就无法访问它们。

Answer 3

在语句之前声明您的变量，使用默认值（来自逻辑的else部分）：

double shippingAmount = shippingDetails * 5.5;
if (shippingInput == 1)
{
    shippingAmount = shippingDetails * 3;
}
else if (shippingInput == 2)
{
    shippingAmount = shippingDetails * 4;
}

Answer 4

您必须在if / else范围内声明shippingAmount：

double shippingAmount = 0;

if (shippingInput == 1)
{
    shippingAmount = shippingDetails * 3;
}
else if (shippingInput == 2)
{
    shippingAmount = shippingDetails * 4;
}
else
{
    shippingAmount = shippingDetails * 5.5;
}

Answer 5

你就是这样做的。

var shippingAmount = (shippingInput == 1) ? shippingDetails * 3 :
                     (shippingInput == 2) ? shippingDetails * 4 :
                                            shippingDetails * 5.5;

Answer 6

您可以将代码改进为DRY，如下所示：

float multiplier;

switch(shippingInput)
{
    case 1: multiplier = 3; break;
    case 2: multiplier = 4; break;
    default: multiplier = 5.5;
}

double shippingAmount = shippingDetails * multiplier;

从if / else语句中获取值？

6 个答案: