我正在尝试遍历结构，而不是遍历字段来创建自动售货机，例如程序。我不明白为什么这行不通：
//create a structure to hold data on the items in the vending machine
struct snack{
string description; //this will hold data on what the item is
int quantity; //this will hold data on how many of the item are left in the vending machine
double cost; //this will hold the cost of this item
};
//...
//create the specific snack structures of type snack and initialize them
snack specificSnack[CHIPS]={"Plain Potato Chips", 15, 1.00};
snack specificSnack[SNICKERS]={"Snickers", 10, 0.75};
snack specificSnack[PEANUTS]={"Peanuts", 15, 1.00};
snack specificSnack[JOLLYRANCHER]={"Jolly Rancher", 10, 0.75};
snack specificSnack[APPLE]={"Apple", 5, 0.50};
//...
//print a header
cout<<"\n# |cost |quantity |item"<<endl:
//display all the items in the menu
for(int i=CHIPS; i<EXIT; i++)
displayMenu(specificSnack[i], i); //call the display for a specific item
请注意，我们还没有覆盖我的课程中的类和对象，因此除了一些简单的I / O东西和字符串类之外，我还无法使用它们。
编辑：筹码，贴纸等。是枚举的变量。
//create an enumerated variable of type treat to make the code more readable and select choices
enum treat{CHIPS, SNICKERS, PEANUTS, JOLLYRANCHER, APPLE, EXIT};
当然，这是完整的代码[更新]：
//This is a simple vending machine emulator
//Developed by [NAME WITHHELD]
//created on: 3/19/2016 8:30 AM
//last updated on: N/A
//library includes
#include <iostream> //in/out functionality
#include <iomanip> //used for in/out manipulators such as endl
#include <string> //used to process string objects
#include <cstring> //used to process c style strings
using namespace std; //this tells the compiler that the libraries are located in the standard location
//create a structure to hold data on the items in the vending machine
struct snack{
string description; //this will hold data on what the item is
int quantity; //this will hold data on how many of the item are left in the vending machine
double cost; //this will hold the cost of this item
};
//create an enumerated variable of type treat to make the code more readable and select choices
enum treat{CHIPS, SNICKERS, PEANUTS, JOLLYRANCHER, APPLE, EXIT};
void vend(int choice, snack & specificSnack);
void finalOutputDisplay(long double totalCost);
treat getChoice();
void displayMenu(snack selection, int i);
//program starts here
int main()
{
//pre-configure cout for numerical output
cout<<fixed;
snack specificSnack[APPLE];
//create the specific snack structures of type snack and initialize them
specificSnack[CHIPS]={"Plain Potato Chips", 15, 1.00};
specificSnack[SNICKERS]={"Snickers", 10, 0.75};
specificSnack[PEANUTS]={"Peanuts", 15, 1.00};
specificSnack[JOLLYRANCHER]={"Jolly Rancher", 10, 0.75};
specificSnack[APPLE]={"Apple", 5, 0.50};
//create a variable to hold the total amount the user is going to spend in this session
long double totalCost=0;
//create and enumerated variable called choice, of type treat
treat choice=CHIPS;
//begin looping until we see the EXIT sentinel
while(choice!=EXIT)
{
//print a header
cout<<"\n# |cost |quantity |item"<<endl;
//display all the items in the menu
for(int i=CHIPS; i<EXIT; i++)
displayMenu(specificSnack[i], i); //call the display for a specific item
//get the user's selection
choice=getChoice();
//skip the vending code if we are exiting
if(choice!=EXIT)
{
//make sure the item isn't sold out
if(specificSnack[choice].quantity!=0)
totalCost=specificSnack[choice].cost;//add the cost of the item chosen to the running total
//run the vending code to decrement the quantity of the item and display
//a message confirming the selection
vend(choice, specificSnack[choice]);
}
}//return to the start of the loop and run a check to see if we break on EXIT
//display the total cost of items bought in this session and
finalOutputDisplay(totalCost);
return 0; //return to the OS
}
void displayMenu(snack selection, int i)
{
//print out one line/option of the menu
//print the cost of the item
cout<<i<<". |"<<setprecision(2)<<setw(6)<<selection.cost<<"|";
//check if we are sold out
if(selection.quantity!=0)
cout<<setprecision(0)<<setw(9)<<selection.quantity<<"|"; //print the amount left
else
cout<<"Sold Out |"; //tell the user we're sold out
//give the item
cout<<selection.description<<endl;
return; //exit function
}
treat getChoice()//get the user's choice, decide if it's valid and what it is, and return it in the proper format
{
//create variables
string usrInput;
treat choice;
int i;
bool continueLoop;
//begin a loop to catch invalid input
do
{
cout<<"\nPlease select an item: "; //prompt the user
i=0; //reset the loop control variable for the uppercase letter to lowercase letter conversion loop
continueLoop=0; //reset the flag to break out of the do-while loop
//get & store user input
getline(cin, usrInput);
//loop through the string
while(usrInput[i]!='\0')
{
//check if the letter is a capital
if(isupper(usrInput[i]))
tolower(usrInput[i]);//convert the character to a lowercase letter
i++;//increment out loop control variable and proceed to the next character in the string
}
//check if the user entered a valid choice and set choice appropriately
if(usrInput=="1" || usrInput=="one" || usrInput=="chips" || usrInput=="plain potato chips")
choice=CHIPS;
else if(usrInput=="2" || usrInput=="two" || usrInput=="snickers")
choice=SNICKERS;
else if(usrInput=="3" || usrInput=="three" || usrInput=="peanuts")
choice=PEANUTS;
else if(usrInput=="4" || usrInput=="four" || usrInput=="jolly rancher")
choice=JOLLYRANCHER;
else if(usrInput=="5" || usrInput=="five" || usrInput=="apple")
choice=APPLE;
else if(usrInput=="6" || usrInput=="six" || usrInput=="exit")
choice=EXIT;
//catch invalid input
else
{
//throw an error message
cout<<"\aERROR! Please enter a valid choice!"<<endl;
//flip the flag to continue the loop again
continueLoop=1;
}
}while(continueLoop);//check if the flag was flipped
return choice;//return the user's choice in the proper format.
}
void vend(int choice, snack & specificSnack)//tell the user what we are vending, or display sold out
{
//give the items name
cout<<"\nITEM: "<<specificSnack.description<<endl;
//give the items price
cout<<"COST: $"<<specificSnack.cost<<endl;
//check if we are sold out and if we aren't run the following code
if(specificSnack.quantity>0)
{
//tell the user we are vending
cout<<"Vending..."<<endl;
//remove one item from the machine
specificSnack.quantity--;
}
//if we are sold out do this:
else
{
//display a sold out message
cout<<"\a\n!SOLD OUT!: "<<specificSnack.description<<endl;
}
return; //exit function
}
void finalOutputDisplay(long double totalCost) //display a final message to the user including their total
{
//be polite & friendly to our customer
cout<<"\nThank you for using this vending machine! Have a nice day!"<<endl;
//display the total spent by the user in this session
cout<<"\nYour total is: "<<totalCost<<endl;
//display a message saying the session is ending
cout<<"\nNow exiting session..."<<endl;
return; //exit function
}
编辑：IT现在可以编译，但是在自动售货机中显示第二个项目时会崩溃
最佳答案
snack specificSnack[CHIPS]={"Plain Potato Chips", 15, 1.00};
考虑一下这在C ++中的含义。
它将specificSnack定义为具有CHIPS类型的snack元素的数组。它不会创建标识为snack的单个specificSnack[CHIPS]。
完成此操作后-假设它可以编译-下一个声明
snack specificSnack[SNICKERS]={"Snickers", 10, 0.75};
将specificSnack定义为具有SNICKERS类型的snack元素的数组。 C ++具有“一个定义规则”，这意味着在定义任何数组时，都只允许一个定义。数组的两个定义-尤其是具有不同维度的数组-打破了该规则。
您最多可以做的就是定义一次数组，然后对其进行初始化。
例如;
enum treat{CHIPS=0, SNICKERS=1, PEANUTS=2, JOLLYRANCHER=3, APPLE=4, EXIT=5, number_of_treats = 5}; // assuming EXIT is not deemed to be a treat
snack specificSnack[number_of_treats] = {
{"Plain Potato Chips", 15, 1.00},
{"Snickers", 10, 0.75},
{"Peanuts", 15, 1.00},
{"Jolly Rancher", 10, 0.75},
{"Apple", 5, 0.50}};