枚举和开关块哪里出错了
Where am I going wrong with Enums & Switchblocks
我正在学习 C++ 作为我在 Uni 课程的一部分。我在 C++ 方面经验不足，但我已经搜索了几个小时的可能解决方案并测试了数百种代码变体，但我仍然无法正常工作。我相信我对枚举的使用从根本上是错误的——我从来没有让它们按照我的预期工作。对于此任务，我们必须使用枚举和 switch 语句。
#include <iostream>
using namespace std;
enum roomType { Deluxe = 250, Twin = 150, Single = 110};
int temp;
int total;
int input = 1; int yes = 1; int no = 0;
void GetInput()
{
cin >> input;
temp = temp*input;
}
int main()
{
if (input != 0)
{
cout << "\nRoom Price Code\n------------------------------------\nDeluxe Room " << "\x9C" << "200 D\nTwin Room " << "\x9C" << "150 T\nSingle " << "\x9C" << "110 S\n\n";
cout << "Enter room type:";
GetInput();
switch (input) {
case Deluxe:
temp = Deluxe;
break;
case Twin:
temp = Twin;
break;
case Single:
temp = Single;
break;
default:
//prevents infinite loop bug
system("pause");
cout << "Entry not recognized";
main();
break;
}
cout << "\nEnter number of rooms:";
GetInput();
cout << "\nEnter number of nights:";
GetInput();
total = total + temp;
cout << "\n\x9C" << total << "\n";
cout << "More rooms? yes/no: ";
cin >> input;
main();
}
cout << "Discount? yes/no: ";
GetInput();
if (input = 1)
{
total = ((total / 100) * 75);
cout << "\n\x9C" << total << "\n";
}
cout << "your total is "<<"\x9C" << total;
system("pause");
system("cls");
return 0;
}
如果用户输入房间类型，例如 Deluxe，case 语句总是默认，如果没有 system("pause"); 将继续陷入循环。
出于某种原因，程序似乎忽略了第一个之后的所有 cin >> input;。我知道这是导致循环的原因。我曾尝试将 cin>> 换成 getline(cin,input) 替代方案，但这似乎也不起作用。
刚刚编译了您的代码。你没有为 Delux 做错任何事。枚举值是 250 而你显示的是 200 只是愚蠢的错误。所以当 运行，你输入 200 并且它变为默认值。
关于第二个问题，为什么程序只运行一次，这是因为你想要那样。检查 if (input != 0) 检查输入类型是否为整数值。您可能在命令行中输入 'yes' 而未进行任何错误检查。尝试输入整数值。
PS: 以后请贴出问题代码。
这段代码中你有很多错误；我将枚举结构化为表示开关选择的枚举值，价格在 case 语句中指定。很多时候你打电话给 main();我从来没有在实践中看到过这样做！我不能说它是无效的或非法的，但我从未见过它！我为正确的概念或想法选择了适当的变量类型，例如某物的成本是 float，当您要求用户输入是否有更多房间或是否有折扣时，我使用了bool 类型。您知道我使用的不会为负的值 unsigned。我删除了所有全局变量（通常是不好的做法）。我修复了一些格式以便于阅读。
这是我所做的，我有一些评论来解释我所做的更改；您需要考虑我所做的其他更改。
#include <iostream>
// using namespace std; // Bad Practice
enum RoomType {
NONE = 0, // NONE For Default Value - No Room Type Selected
DELUXE,
TWIN,
SINGLE,
LAST // MUST BE LAST!
};
/*void GetInput() { // Function Not Really Required In This Simple Application
cin >> input;
temp = temp*input;
}*/
int main() {
while ( true ) {
float totalCost = 0; // Renamed Variable For Better Readability
int input = 0; // Initialized To 0, We Do Not Know What The User Will Choice
std::cout << std::endl << "Room Price Code" << std::endl
<< "------------------------------------" << std::endl
<< "Deluxe Room " << "\x9C" << "250 D" << std::endl
<< "Twin Room " << "\x9C" << "150 T" << std::endl
<< "Single " << "\x9C" << "110 S" << std::endl << std::endl;
std::cout << "Please Make A Selection:" << std::endl
<< "1 - Deluxe" << std::endl
<< "2 - Twin" << std::endl
<< "3 - Single" << std::endl << std::endl;
std::cin >> input;
// You Never Declare Variable Type Of RoomType
RoomType type = static_cast<RoomType>( input ); // Cast input to RoomType
float costOfRoom = 0.0f;
switch (type) {
case NONE: {
costOfRoom = 0.0f;
break;
}
case DELUXE: {
costOfRoom = 250.0f;
break;
}
case TWIN: {
costOfRoom = 150.0f;
break;
}
case SINGLE: {
costOfRoom = 110.0f;
break;
}
default: {
std::cout << "Entry not recognized";
//main(); wrong
break;
}
} // Switch
unsigned numRooms = 0;
unsigned numNights = 0;
std::cout << std::endl << "Enter number of rooms:";
std::cin >> numRooms;
std::cout << std::endl << "Enter number of nights:";
std::cin >> numNights;
totalCost = costOfRoom * numNights * numRooms;
std::cout << "\n\x9C" << totalCost << "\n";
bool moreRooms = false;
bool hasDiscount = false;
input = 0;
std::cout << "More rooms? 1 for yes - 0 for no: ";
std::cin >> moreRooms;
if ( moreRooms ) {
std::cout << "Please Enter Number Of Rooms. ";
std::cin >> input;
totalCost += (costOfRoom * numNights * input);
}
// main(); // Wrong!
std::cout << "Discount? 1 for yes - 0 for no: ";
std::cin >> hasDiscount;
if ( hasDiscount ) {
totalCost = ((totalCost / 100) * 75);
std::cout << std::endl << "\x9C" << totalCost << std::endl;
}
std::cout << "Your total is " <<"\x9C" << totalCost << std::endl;
bool runAgain = false;
std::cout << std::endl << "Would you like to contine? 1 - yes - 0 for no:";
std::cin >> runAgain;
if ( !runAgain ) {
break;
}
} // while
system("pause");
system("cls");
return 0;
} // main
注意：这并没有直接回答用户的问题；我已经在上面做到了。这是一个基于用户回复之一的示例，用于演示枚举和枚举类型的使用，以便他们能够更轻松、更好地理解它们。
这里有两个函数原型，它们可以做同样的事情，一个使用枚举，而另一个不使用。
enum ProductType {
HARDWARE = 1,
TOOLS,
APPLIANCES,
FURNITURE,
LAWN_AND_GARDEN,
PAINT
};
// This Version Doesn't Use An Enumerated Value And Takes In An Unsigned Int
float calculateProductTotalCost( unsigned int productType, float costOfProduct, unsigned int numberOfItems );
float calculateProductTotalCost( ProductType type, float costOfProduct, unsigned int numberOfItems );
someOtherFunction() { // Could be main()
// This function has a magic number to represent the product type
calcluateProductTotalCost( 3, 1499.99f, 2 );
// This version uses the enumeration with the scope resolution operator
// to allow the calling of this function to be easier to read.
calculateProductTotalCost( ProductType::PAINT, 23.50f, 150 );
// Although I did not show any implementation for these functions
// since that is irrelevant, the importance of the two is that in
// practice these methods would be the same and perform the same
// exact calculation and operation. It is just more readable for
// another human to see your code when they have to work on it
// sometime in the future and you are not there to explain what you
// did and why you did it. It can even be a help for yourself if
// you go back to code that you have written that you have not seen
// in a few months or years. Then just by reading the Wording
// of the Enumeration you know that this value represents this specific
// object.
}
这是另一个例子
SoundSource {
CLAP = 1,
BANG,
GUN_SHOT,
THUNDER_BOLT,
LAUGHTER,
SCREAM,
};
bool playSound( unsigned int, bool bLoop );
bool playSound( SoundSource, bool bLoop );
someFunction() {
// Which group of function calls looks better and is easier to understand; Group A or Group B?
// Group A
playSound( 6, false );
playSound( 4, true );
playSound( 3, false );
// Group B
playSound( SoundSource::THUNDER_BOLT, true );
playSound( SoundSource::SCREAM, false );
playSound( SoundSource::LAUGH, true );
}
希望本文能帮助您理解枚举的用途；它们适用于一些不同的事情，适用于 switch case 语句，并且允许通常由 ID 值（通常是无符号的）传递的不同数据类型也由作为枚举值的单词表示。如果您注意到将枚举中的所有值命名为 ALL_CAPS 是一种很好的做法，请用下划线分隔每个单词；但这也只是偏好，但大多数人在看到全部大写时都会将其识别为枚举。
我正在学习 C++ 作为我在 Uni 课程的一部分。我在 C++ 方面经验不足，但我已经搜索了几个小时的可能解决方案并测试了数百种代码变体，但我仍然无法正常工作。我相信我对枚举的使用从根本上是错误的——我从来没有让它们按照我的预期工作。对于此任务，我们必须使用枚举和 switch 语句。
#include <iostream>
using namespace std;
enum roomType { Deluxe = 250, Twin = 150, Single = 110};
int temp;
int total;
int input = 1; int yes = 1; int no = 0;
void GetInput()
{
cin >> input;
temp = temp*input;
}
int main()
{
if (input != 0)
{
cout << "\nRoom Price Code\n------------------------------------\nDeluxe Room " << "\x9C" << "200 D\nTwin Room " << "\x9C" << "150 T\nSingle " << "\x9C" << "110 S\n\n";
cout << "Enter room type:";
GetInput();
switch (input) {
case Deluxe:
temp = Deluxe;
break;
case Twin:
temp = Twin;
break;
case Single:
temp = Single;
break;
default:
//prevents infinite loop bug
system("pause");
cout << "Entry not recognized";
main();
break;
}
cout << "\nEnter number of rooms:";
GetInput();
cout << "\nEnter number of nights:";
GetInput();
total = total + temp;
cout << "\n\x9C" << total << "\n";
cout << "More rooms? yes/no: ";
cin >> input;
main();
}
cout << "Discount? yes/no: ";
GetInput();
if (input = 1)
{
total = ((total / 100) * 75);
cout << "\n\x9C" << total << "\n";
}
cout << "your total is "<<"\x9C" << total;
system("pause");
system("cls");
return 0;
}
如果用户输入房间类型，例如 Deluxe，case 语句总是默认，如果没有 system("pause"); 将继续陷入循环。
出于某种原因，程序似乎忽略了第一个之后的所有 cin >> input;。我知道这是导致循环的原因。我曾尝试将 cin>> 换成 getline(cin,input) 替代方案，但这似乎也不起作用。
刚刚编译了您的代码。你没有为 Delux 做错任何事。枚举值是 250 而你显示的是 200 只是愚蠢的错误。所以当 运行，你输入 200 并且它变为默认值。
关于第二个问题，为什么程序只运行一次，这是因为你想要那样。检查 if (input != 0) 检查输入类型是否为整数值。您可能在命令行中输入 'yes' 而未进行任何错误检查。尝试输入整数值。
PS: 以后请贴出问题代码。
这段代码中你有很多错误；我将枚举结构化为表示开关选择的枚举值，价格在 case 语句中指定。很多时候你打电话给 main();我从来没有在实践中看到过这样做！我不能说它是无效的或非法的，但我从未见过它！我为正确的概念或想法选择了适当的变量类型，例如某物的成本是 float，当您要求用户输入是否有更多房间或是否有折扣时，我使用了bool 类型。您知道我使用的不会为负的值 unsigned。我删除了所有全局变量（通常是不好的做法）。我修复了一些格式以便于阅读。
这是我所做的，我有一些评论来解释我所做的更改；您需要考虑我所做的其他更改。
#include <iostream>
// using namespace std; // Bad Practice
enum RoomType {
NONE = 0, // NONE For Default Value - No Room Type Selected
DELUXE,
TWIN,
SINGLE,
LAST // MUST BE LAST!
};
/*void GetInput() { // Function Not Really Required In This Simple Application
cin >> input;
temp = temp*input;
}*/
int main() {
while ( true ) {
float totalCost = 0; // Renamed Variable For Better Readability
int input = 0; // Initialized To 0, We Do Not Know What The User Will Choice
std::cout << std::endl << "Room Price Code" << std::endl
<< "------------------------------------" << std::endl
<< "Deluxe Room " << "\x9C" << "250 D" << std::endl
<< "Twin Room " << "\x9C" << "150 T" << std::endl
<< "Single " << "\x9C" << "110 S" << std::endl << std::endl;
std::cout << "Please Make A Selection:" << std::endl
<< "1 - Deluxe" << std::endl
<< "2 - Twin" << std::endl
<< "3 - Single" << std::endl << std::endl;
std::cin >> input;
// You Never Declare Variable Type Of RoomType
RoomType type = static_cast<RoomType>( input ); // Cast input to RoomType
float costOfRoom = 0.0f;
switch (type) {
case NONE: {
costOfRoom = 0.0f;
break;
}
case DELUXE: {
costOfRoom = 250.0f;
break;
}
case TWIN: {
costOfRoom = 150.0f;
break;
}
case SINGLE: {
costOfRoom = 110.0f;
break;
}
default: {
std::cout << "Entry not recognized";
//main(); wrong
break;
}
} // Switch
unsigned numRooms = 0;
unsigned numNights = 0;
std::cout << std::endl << "Enter number of rooms:";
std::cin >> numRooms;
std::cout << std::endl << "Enter number of nights:";
std::cin >> numNights;
totalCost = costOfRoom * numNights * numRooms;
std::cout << "\n\x9C" << totalCost << "\n";
bool moreRooms = false;
bool hasDiscount = false;
input = 0;
std::cout << "More rooms? 1 for yes - 0 for no: ";
std::cin >> moreRooms;
if ( moreRooms ) {
std::cout << "Please Enter Number Of Rooms. ";
std::cin >> input;
totalCost += (costOfRoom * numNights * input);
}
// main(); // Wrong!
std::cout << "Discount? 1 for yes - 0 for no: ";
std::cin >> hasDiscount;
if ( hasDiscount ) {
totalCost = ((totalCost / 100) * 75);
std::cout << std::endl << "\x9C" << totalCost << std::endl;
}
std::cout << "Your total is " <<"\x9C" << totalCost << std::endl;
bool runAgain = false;
std::cout << std::endl << "Would you like to contine? 1 - yes - 0 for no:";
std::cin >> runAgain;
if ( !runAgain ) {
break;
}
} // while
system("pause");
system("cls");
return 0;
} // main
注意：这并没有直接回答用户的问题；我已经在上面做到了。这是一个基于用户回复之一的示例，用于演示枚举和枚举类型的使用，以便他们能够更轻松、更好地理解它们。
这里有两个函数原型，它们可以做同样的事情，一个使用枚举，而另一个不使用。
enum ProductType {
HARDWARE = 1,
TOOLS,
APPLIANCES,
FURNITURE,
LAWN_AND_GARDEN,
PAINT
};
// This Version Doesn't Use An Enumerated Value And Takes In An Unsigned Int
float calculateProductTotalCost( unsigned int productType, float costOfProduct, unsigned int numberOfItems );
float calculateProductTotalCost( ProductType type, float costOfProduct, unsigned int numberOfItems );
someOtherFunction() { // Could be main()
// This function has a magic number to represent the product type
calcluateProductTotalCost( 3, 1499.99f, 2 );
// This version uses the enumeration with the scope resolution operator
// to allow the calling of this function to be easier to read.
calculateProductTotalCost( ProductType::PAINT, 23.50f, 150 );
// Although I did not show any implementation for these functions
// since that is irrelevant, the importance of the two is that in
// practice these methods would be the same and perform the same
// exact calculation and operation. It is just more readable for
// another human to see your code when they have to work on it
// sometime in the future and you are not there to explain what you
// did and why you did it. It can even be a help for yourself if
// you go back to code that you have written that you have not seen
// in a few months or years. Then just by reading the Wording
// of the Enumeration you know that this value represents this specific
// object.
}
这是另一个例子
SoundSource {
CLAP = 1,
BANG,
GUN_SHOT,
THUNDER_BOLT,
LAUGHTER,
SCREAM,
};
bool playSound( unsigned int, bool bLoop );
bool playSound( SoundSource, bool bLoop );
someFunction() {
// Which group of function calls looks better and is easier to understand; Group A or Group B?
// Group A
playSound( 6, false );
playSound( 4, true );
playSound( 3, false );
// Group B
playSound( SoundSource::THUNDER_BOLT, true );
playSound( SoundSource::SCREAM, false );
playSound( SoundSource::LAUGH, true );
}
希望本文能帮助您理解枚举的用途；它们适用于一些不同的事情，适用于 switch case 语句，并且允许通常由 ID 值（通常是无符号的）传递的不同数据类型也由作为枚举值的单词表示。如果您注意到将枚举中的所有值命名为 ALL_CAPS 是一种很好的做法，请用下划线分隔每个单词；但这也只是偏好，但大多数人在看到全部大写时都会将其识别为枚举。