c++ - 无法分离头文件和 cpp 文件(包含错误和代码)

Question

这是我的代码中的文件。如果我注释掉所有 data.cpp 并将函数粘贴到类下的 data.h 头文件中，它编译得很好。但是当我这样做时，它是分开的，我得到了这个错误。

duplicate symbol _salesData in:.../SalesData.build/Objects-normal/x86_64/main.o
.../SalesData.build/Objects-normal/x86_64/Data.o
ld: 1 duplicate symbol for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)" 

所以我删除了 main.cpp 上的#include "data.h"并注释掉了函数调用，它编译了，但它显然没有执行我想要它执行的操作。我不明白我怎么有重复的符号。 这是我的文件...

//data.h
#ifndef __SalesData__Data__
#define __SalesData__Data__

#include <iostream>
#include <stdlib.h>

class Data {
public:
    //[0] = day DD, [1] = month MM, [2] = year YYYY
    float data[32][13][9999];
    void newData();
    void editData();
    float viewData();
}salesData;

#endif /* defined(__SalesData__Data__) */

...

//data.cpp
#include "Data.h"

void Data::editData() {
    unsigned short day;
    unsigned short month;
    unsigned short year;
    float dailySales;
    printf("\nSelect Day: ");
    printf("\n>> ");
    std::cin >> day;
    printf("\nSelect Month: ");
    printf("\n>> ");
    std::cin >> month;
    printf("\nSelect Year: ");
    printf("\n>> ");
    std::cin >> year;
    printf("\nEnter Daily Sales: ");
    printf("\n>> ");
    if ((data[day][month][year])) {
        std::cin >> dailySales;
        data[day][month][year] = dailySales;
    }
    else {
        printf("\nSales have not been recorded for this date. If you wish to input type 'yes' else press any other key");
        std::string choice;
        std::cin >> choice;
        if (choice == "yes") {
            newData();
        }
    }
}
//... same for other class functions

...

//main.cpp
#include <iostream>
#include <stdlib.h>
#include "Data.h"

void selectMain() {

    char choice;
    while (1) {
        printf("Please select an option.");
        printf("\n1. Input Data");
        printf("\n2. View Data");
        printf("\n3. Edit Data");
        printf("\n>> ");
        std::cin >> choice;
        switch (choice) {
            case '1':
                salesData.newData();
                return;
            case '2':
                salesData.viewData();
                return;
            case '3':
                salesData.editData();
                return;
            default:
                printf("\nInvalid Choice. ");
                continue;
        }
    }
}

int main(int argc, const char * argv[])
{
    char endChar;
    while (endChar != '`') {
        selectMain();
        printf("\nPress any key to continue or '`' to end the program.\n");
        std::cin >> endChar;
    }
    printf("\nProgram Ended");
    return 0;
}

Answer 1

问题是因为您在类声明后在头文件中定义变量 salesData 的方式。因此，它在 data.cpp 文件和您的 main.cpp 文件中都有定义。将 salesData 变量移动到 main.cpp