混淆编译器错误

确定如果需要，我会添加代码，但通常我很体面地弄清楚错误。但是我得到的这是非常令人困惑的。我正在使用三个文件。驱动程序代码citysim.cpp和两个支持文件utils.cpp和utils.h。我猜这是由于我在协调它们之间做错事的事实。

错误如下

g++ -g -Wall -o citysim citysim.o utils.o
utils.o: In function `map_of_cities::read(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)':
/home/rryder1/cs302/labs/lab4/utils.cpp:95: multiple definition of `map_of_cities::read(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'
citysim.o:/home/rryder1/cs302/labs/lab4/utils.h:61: first defined here
citysim.o: In function `map_of_cities::read(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)':
citysim.cpp:(.text+0xcb): undefined reference to `city::city()'
citysim.cpp:(.text+0x244): undefined reference to `city::~city()'
citysim.cpp:(.text+0x2a3): undefined reference to `city::~city()'
citysim.o: In function `std::vector<city, std::allocator<city> >::_M_insert_aux(__gnu_cxx::__normal_iterator<city*, std::vector<city, std::allocator<city> > >, city const&)':
citysim.cpp:(.text._ZNSt6vectorI4citySaIS0_EE13_M_insert_auxEN9__gnu_cxx17__normal_iteratorIPS0_S2_EERKS0_[std::vector<city, std::allocator<city> >::_M_insert_aux(__gnu_cxx::__normal_iterator<city*, std::vector<city, std::allocator<city> > >, city const&)]+0xd2): undefined reference to `city::~city()'
citysim.cpp:(.text._ZNSt6vectorI4citySaIS0_EE13_M_insert_auxEN9__gnu_cxx17__normal_iteratorIPS0_S2_EERKS0_[std::vector<city, std::allocator<city> >::_M_insert_aux(__gnu_cxx::__normal_iterator<city*, std::vector<city, std::allocator<city> > >, city const&)]+0x27d): undefined reference to `city::~city()'
citysim.o: In function `__gnu_cxx::new_allocator<city>::destroy(city*)':
citysim.cpp:(.text._ZN9__gnu_cxx13new_allocatorI4cityE7destroyEPS1_[__gnu_cxx::new_allocator<city>::destroy(city*)]+0x18): undefined reference to `city::~city()'
citysim.o:citysim.cpp:(.text._ZSt8_DestroyI4cityEvPT_[void std::_Destroy<city>(city*)]+0x14): more undefined references to `city::~city()' follow
utils.o: In function `map_of_cities::read(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)':
utils.cpp:(.text+0xacd): undefined reference to `city::city()'
utils.cpp:(.text+0xc68): undefined reference to `city::~city()'
utils.cpp:(.text+0xcc7): undefined reference to `city::~city()'
collect2: ld returned 1 exit status

它可能源于的一件事是，我不确定如何将utils.cpp与utils.h联系起来，或者如果需要的话。我习惯于将所有内容写入一个CPP文件中。utils.cpp和citysim.cpp都包含utils.h的语句。utils.h基本上只有类定义和功能标头。utils.cpp包含所有函数定义，citySim.cpp包含主要功能。

这是我的utils.h文件

#ifndef __CITY_DEFS_H__
#define __CITY_DEFS_H__
#include <string>
#include <fstream>
#include <iostream>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <vector>
#include <iomanip>
using namespace std;
//#include ALL HEADER FILES NEEDED FOR THIS HEADER FILE
class city {
  friend ostream &operator<<(ostream &, const city &);
  //OTHER FRIENDS
  friend class map_of_cities;
  public:
    city();
    ~city();
    // MEMBER FUNCTIONS
  protected:
    // MEMBER DATA
    string Name, type;
    float latitude, longitude;
    int population, listlocation;

    // MEMBER FUNCTIONS
};

ostream &operator<<(ostream &, const city &);
//OTHER CLASS DEFINITIONS
class map_of_cities {
    public:
        map_of_cities();
        ~map_of_cities();
        void read(string fname);
        float distance(city one, city two);
        void populatelists();
        void print();
        int listpop(vector<city> list);
    private:
        vector<city> cities;
        vector<city> local;
        vector<city> regional;
        vector<city> global;
};
#endif

如果我需要包括我可以的其他文件，但是utils.cpp非常大，只是一团糟。我的问题是吗？