[英]Use of unassigned local variable
我必须建立一个程序来获取比萨饼的直径,并找到它可以容纳多少个切片以及每个切片的面积(比萨饼),它用常数定义比萨饼的大小,但是“ int numberOfSlice”却出错了是说使用未分配的局部变量,甚至认为是在分配if语句。
class Program
{
static void Main(string[] args)
{
//declarations of Constans
const int SMALL_MIN = 12;
const int SMALL_MED = 16;
const int MED_LARGE = 24;
const int LARGE_XLARGE = 30;
const int XL_MAX = 36;
const int SMALL_SLICE = 8;
const int MED_SLICE = 12;
const int LARGE_SLICE = 16;
const int XL_SLICES = 24;
//declarations of varable
double pizzaDiameter;
int numberOfSlices = 0;
double sliceArea;
double radius;
string userInput = " ";
Console.WriteLine("Please enter the diameter of your pizza:"); // tell user to input diameter
userInput = Console.ReadLine(); // gets userinput
double.TryParse(userInput, out pizzaDiameter); // see if userinput is vaild
if (pizzaDiameter >= SMALL_MIN && pizzaDiameter <= XL_MAX) // if in range will continue
{
// all the ranges for the pizzas
if (pizzaDiameter >= SMALL_MIN && pizzaDiameter < SMALL_MED)
{
numberOfSlices = (SMALL_SLICE);
}
else if (pizzaDiameter >= SMALL_MED && pizzaDiameter < MED_LARGE)
{
numberOfSlices = (MED_SLICE);
}
else if (pizzaDiameter >= MED_SLICE && pizzaDiameter < LARGE_XLARGE)
{
numberOfSlices = (LARGE_SLICE);
}
else if (pizzaDiameter >= LARGE_XLARGE && pizzaDiameter <= XL_MAX)
{
numberOfSlices = (XL_SLICES);
}
radius = pizzaDiameter / 2; // divides pizzaDiameter to get radius
sliceArea = Math.PI * Math.Pow(radius, 2) / numberOfSlices; // gets slice area
sliceArea = Math.Round(sliceArea, 2); // rounds to 2 places
// output of resluts
Console.WriteLine("\nA diameter of " + pizzaDiameter + " will yield " + numberOfSlices + " slices.");
Console.WriteLine("\nEach slice will have an area of " + sliceArea + "\".");
Console.WriteLine("\nPress any key to exit..."); // tells user to end program
Console.ReadKey(); // readkey to end program
}
else // if the diameter was not in range will display this error
{
Console.WriteLine("\nEntry Error ");
Console.WriteLine("\nPizza must have a diameter in the range of 12\" to 36\" inclusive!");
Console.WriteLine("please try again");
Console.WriteLine("\nPress any key to end this application...");// tells user to end program
Console.ReadKey(); // readkey to end program
}
}
}
}
错误告诉您所有您需要了解的内容。 您的numberOfSlices
变量未正确初始化。 使用它之前,必须在每个可能的代码路径中为其分配一个值。
尝试在声明时对其进行初始化:
int numberOfSlices = 0;
或者,您可以更仔细地构造if
-block以避免此错误:
if (pizzaDiameter <= XL_MAX || pizzaDiameter >= SMALL_MIN)
{
if (pizzaDiameter >= SMALL_MIN || pizzaDiameter < SMALL_MED)
{
numberOfSlices = (SMALL_SLICE);
}
...
else // Note, you do not need the final `if` in this block
{
numberOfSlices = (XL_SLICES);
}
radius = pizzaDiameter/2;
sliceArea = Math.PI * Math.Pow(radius, 2);
Console.WriteLine("\nA diameter of " + pizzaDiameter + " will yield." + numberOfSlices + " slices.");
Console.WriteLine("\nEach slice will have an area of " + sliceArea + "\".");
Console.WriteLine("\nPress any key to exit...");
Console.ReadKey();
}
else
{
Console.WriteLine(" Entry Error ");
Console.WriteLine("Pizza must have args diameter in the range of 12\" to 36\" inclusive!");
Console.WriteLine("please try again");
Console.WriteLine(" /nPress any key to end this application...");
Console.ReadKey();
}
在此代码中, numberOfSlices
仅在if
块内部if
,该块保证在使用之前为其分配值。
该变量仍未在外部else
块中分配:
if (pizzaDiameter <= XL_MAX || pizzaDiameter >= SMALL_MIN)
{
}
else
{
// unassigned here
}
如果if (pizzaDiameter <= XL_MAX || pizzaDiameter >= SMALL_MIN)
返回false,那么numberOfSlices
不会被分配,并且以下行将失败。
Console.WriteLine("\nA diameter of " + pizzaDiameter + " will yield." + numberOfSlices + " slices.");
之所以得到该错误,是因为您仅在if块中分配了它。
如果不满足条件怎么办? 在那种情况下,它不会被初始化,因此会抛出该错误。
编译器会在使用任何变量之前检查每个可能的代码路径中的分配。
您需要做的是
int numberOfSlices=0; // Or whatever initial value you want to give
if (pizzaDiameter <= XL_MAX || pizzaDiameter >= SMALL_MIN)
{
}
else
{
}
//Then, even if you try to access it here, it won't throw any error.
注意:它不是由int的默认值 (即0)初始化的,因为它不是类的数据成员。
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