構造体をループする必要があります

Question

私はプログラムのような自動販売機を作成するためのフィールドではなく、構造体をループしようとしています。これがうまくいかない理由を私は理解していない：

//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 

我々はまだ私のクラスでクラスとオブジェクトをカバーしていないので、私はいくつかの単純なI/Oのものを除いて、まだそれらを使用することはできませんのでご注意くださいおよび文字列クラスです。

EDIT：CHIPS、SNICKERSなどは列挙変数です。

//create an enumerated variable of type treat to make the code more readable and select choices 
enum treat{CHIPS, SNICKERS, PEANUTS, JOLLYRANCHER, APPLE, EXIT}; 

確かに、ここでは完全なコードだ[UPDATED]：

//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 
} 

EDIT：ITは、今コンパイルし、それは自動販売機で

Answer 1

を2番目の項目を表示するクラッシュ私はあなたが何を意味するかと思います次のとおりです。

... 
enum treat{CHIPS=0, SNICKERS=1, PEANUTS=2, JOLLYRANCHER=3, APPLE=4, EXIT=5}; 
... 
int main() { 
    ... 
    snack specificSnack[6]; 
    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}; 
    ... 
} 

Answer 2

snack specificSnack[CHIPS]={"Plain Potato Chips", 15, 1.00};

これがC++で何を意味するかを考えてみましょう。

snackのCHIPS要素を持つ配列としてspecificSnackを定義しています。 specificSnack[CHIPS]と識別される単一のsnackは作成されません。これを行った後

- それがコンパイル仮定 - 次の宣言

snack specificSnack[SNICKERS]={"Snickers", 10, 0.75};

型snackのSNICKERS要素を持つ配列として定義specificSnack。 C++には「1つの定義ルール」があります。つまり、配列を定義するときに、1つの定義だけが許可されます。配列の2つの定義 - 特に異なる次元の - は、その規則を破ります。

最も可能なのは、アレイを一度定義してから初期化することです。

たとえば、

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}};