我查了一下我的问题无济于事所以我在这里专门问。当我运行我的代码，它需要一部分并查看部件文件时，它是部件类，有多少部件，以及它的成本，它应该告诉我它在文件中的位置以及它是否不是，将它添加到文件中。在我的教授的帮助下，我纠正了很多错误，但我仍然得到了未解决的外部错误。确切地说是五个。我真的不明白这意味着什么。这是代码和错误：
#include <iostream>
#include <fstream>
#include <iomanip>
#include <vector>
#include <fstream>
#include <string>
#include <algorithm>
using namespace std;
// Sorts vectors (Calls swapper)
void sort(vector<string>& part_number, vector<char>& part_class, vector<int>&ohb, vector<double>& cost);
// Fills vectors
bool get_data (vector <string>& part_number, vector <char>& part_class, vector<int>& part_ohb, vector <double>& part_cost);
// Does a binary search
int bin_search(string key, const vector<string>& part_number);
// Asks user for a part number to search for
void get_target();
// Gets remaining info to add a part number
void get_more_data(char& class_in,int& part_ohb_in,double& part_cost_in);
// Inserts part number data into vectors into the proper location (code for this given below)
void insert_data (vector <string>& part_number, vector <char>& part_class, vector <int>& part_ohb, vector <double>& part_cost, string part_in, char class_in, int part_ohb_in, double part_cost_in);
// Displays info on part number
void display (const vector <string>& part_number, const vector <char>& part_class, const vector <int>& part_ohb, const vector <double>& part_cost, int finder);
// Prints search stats
void print_stats(int searches, int good, int bad);
// Writes out file
void put_data (const vector <string>& part_number, const vector <char>& part_class, const vector <int>& part_ohb, const vector <double>& part_cost);
// Templated swap function. Swaps two items in a vector of any type
template <class CType> void swapper (CType& a, CType & b);
int main() {
vector <string> part_number;
vector <char> part_class;
vector <int> part_ohb;
vector <double> part_cost;
string key, part_in;
int part_ohb_in, searches, good, bad, finder;
char class_in, response;
double part_cost_in;
do {
get_target();
searches++;
get_data (part_number, part_class, part_ohb, part_cost);
sort(part_number, part_class, part_ohb, part_cost);
finder = bin_search(key, part_number);
if (finder == -1) {
cout << part_in << "not found!\n";
get_more_data(class_in, part_ohb_in, part_cost_in);
cout << "Adding part into library...\n";
bad++;
insert_data (part_number, part_class, part_ohb, part_cost, part_in, class_in, part_ohb_in, part_cost_in);
sort(part_number, part_class, part_ohb, part_cost);
}
else {
display (part_number, part_class, part_ohb, part_cost, finder);
good++;
}
cout << "Would you like to search again?" << endl;
} while (toupper(response) != 'Y');
print_stats(searches, good, bad);
put_data (part_number, part_class, part_ohb, part_cost);
return 0;
}
void sort(vector<string>& part_number, vector<char>& part_class, vector<int>& part_ohb, vector<double>& part_cost) {
int i, j, increment;
string temp_pn;
char temp_pc;
int temp_ohb;
double temp_cost;
increment = 3;
while (increment > 0) {
for (i=0; i < part_number.size(); i++) {
j = i;
swapper(temp_pn, part_number[i]);
swapper(temp_pc, part_class[i]);
swapper(temp_ohb, part_ohb[i]);
swapper(temp_cost, part_cost[i]);
while ((j >= increment) && (part_number[j-increment] > temp_pn)) {
swapper(part_number[j], part_number[j - increment]);
swapper(part_class[j], part_class[j - increment]);
swapper(part_ohb[j], part_ohb[j - increment]);
swapper(part_cost[j], part_cost[j - increment]);
j = j - increment;
}
swapper( part_number[j], temp_pn);
swapper( part_class[j], temp_pc);
swapper( part_ohb[j], temp_ohb);
swapper( part_cost[j], temp_cost);
}
if (increment/2 != 0) {
increment = increment/2;
}
else if (increment == 1) {
increment = 0;
}
else {
increment = 1;
}
}
}
bool get_data (vector <string>& part_number, vector <char>& part_class, vector <int>& part_ohb, vector <double>& part_cost) {
bool OK = true;
string partIn;
int ohbIn;
char classIn;
double costIn;
ifstream myFile;
myFile.open("parts.txt");
if (myFile.fail()) {
OK = false;
}
else {
while(myFile >> partIn >> classIn >> ohbIn >> costIn) {
part_number.push_back(partIn);
part_class.push_back(classIn);
part_ohb.push_back(ohbIn);
part_cost.push_back(costIn);
myFile.close();
}
}
return OK;
}
int bin_search(string key, const vector<string>& part_number) {
bool found = false;
int first, mid, last, return_val;
first = 0;
last = part_number.size()-1;
while ((first <= last) && (!found)) {
mid = (first + last) / 2;
if (key == part_number[mid]) {
found = true;
}
else {
if (key < part_number[mid]) {
last = mid - 1;
}
else {
first = mid + 1;
}
}
}
if (found) {
return_val = mid;
}
else {
return_val = -1;
}
return return_val;
}
void get_target(string& key) {
cout << "What part number should I search for?" << endl;
cin >> key;
}
void get_more_data(char& class_in, int& part_ohb_in, double& part_cost_in) {
cout << "Please add in the part class, how many of them there are, and the cost per part: ";
cin >> class_in >> part_ohb_in >> part_cost_in;
}
void insert_data (vector <string>& part_number, vector <char>& part_class, vector <int>& part_ohb, vector <double>& part_cost, string part_in, char class_in, int part_ohb_in, double part_cost_in) {
part_number.push_back(part_in);
part_class.push_back(class_in);
part_ohb.push_back(part_ohb_in);
part_cost.push_back(part_cost_in);
}
void display (const vector <string>& part_number, const vector <char>& part_class, const vector <int>& part_ohb, const vector <double>& part_cost, int finder) {
int total = part_ohb[finder] * part_cost[finder];
cout << "There are " << part_ohb[finder] << " of Part Number " << part_number[finder] << " in inventory. It is a class " << part_class[finder] << " part. The cost is " << part_cost[finder] << ". The value of that inventory is " << total << ".\n";
}
void print_stats(int searches, int good, int bad) {
cout << "You made " << searches << " searches with " << good << " successful searches and " << bad << " bad searches.\n";
}
void put_data (const vector <string>& part_number, const vector <char>& part_class, const vector <int>& part_ohb, const vector <double>& part_cost) {
// for loop for displaying
ofstream myfile;
myfile.open ("parts.txt");
for (int i = 0; i < part_number.size(); i++) {
myfile << part_number[i] << " " << part_class[i] << " " << part_ohb[i] << " " << part_cost[i] << endl;
}
myfile.close();
}
错误：
1>Project3Source.obj : error LNK2019: unresolved external symbol "void __cdecl get_target(void)" (?get_target@@YAXXZ) referenced in function _main
1>Project3Source.obj : error LNK2019: unresolved external symbol "void __cdecl swapper<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > >(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > &)" (??$swapper@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@@YAXAAV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@0@Z) referenced in function "void __cdecl sort(class std::vector<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class std::allocator<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > > &,class std::vector<char,class std::allocator<char> > &,class std::vector<int,class std::allocator<int> > &,class std::vector<double,class std::allocator<double> > &)" (?sort@@YAXAAV?$vector@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@V?$allocator@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@@std@@AAV?$vector@DV?$allocator@D@std@@@2@AAV?$vector@HV?$allocator@H@std@@@2@AAV?$vector@NV?$allocator@N@std@@@2@@Z)
1>Project3Source.obj : error LNK2019: unresolved external symbol "void __cdecl swapper<char>(char &,char &)" (??$swapper@D@@YAXAAD0@Z) referenced in function "void __cdecl sort(class std::vector<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class std::allocator<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > > &,class std::vector<char,class std::allocator<char> > &,class std::vector<int,class std::allocator<int> > &,class std::vector<double,class std::allocator<double> > &)" (?sort@@YAXAAV?$vector@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@V?$allocator@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@@std@@AAV?$vector@DV?$allocator@D@std@@@2@AAV?$vector@HV?$allocator@H@std@@@2@AAV?$vector@NV?$allocator@N@std@@@2@@Z)
1>Project3Source.obj : error LNK2019: unresolved external symbol "void __cdecl swapper<int>(int &,int &)" (??$swapper@H@@YAXAAH0@Z) referenced in function "void __cdecl sort(class std::vector<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class std::allocator<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > > &,class std::vector<char,class std::allocator<char> > &,class std::vector<int,class std::allocator<int> > &,class std::vector<double,class std::allocator<double> > &)" (?sort@@YAXAAV?$vector@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@V?$allocator@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@@std@@AAV?$vector@DV?$allocator@D@std@@@2@AAV?$vector@HV?$allocator@H@std@@@2@AAV?$vector@NV?$allocator@N@std@@@2@@Z)
1>Project3Source.obj : error LNK2019: unresolved external symbol "void __cdecl swapper<double>(double &,double &)" (??$swapper@N@@YAXAAN0@Z) referenced in function "void __cdecl sort(class std::vector<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class std::allocator<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > > &,class std::vector<char,class std::allocator<char> > &,class std::vector<int,class std::allocator<int> > &,class std::vector<double,class std::allocator<double> > &)" (?sort@@YAXAAV?$vector@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@V?$allocator@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@@std@@AAV?$vector@DV?$allocator@D@std@@@2@AAV?$vector@HV?$allocator@H@std@@@2@AAV?$vector@NV?$allocator@N@std@@@2@@Z)
1>C:\Users\Austin Julio\Desktop\CMPSC 121\Projects\Project 3\Debug\Project 3.exe : fatal error LNK1120: 5 unresolved externals
答案 0 :(得分：2)
您已宣布swapper
// templated swap function Swaps two items in a vector of any type
template <class CType>
void swapper (CType& a, CType & b);
但你永远不会定义它。因此，当您的程序调用{{1}}时，编译器期望在链接时提供定义。链接器尝试查找符号（即函数），但找不到它。
与其他未声明的功能相同。要修复它们，您需要编写适当的函数。
答案 1 :(得分：1)
未解析的外部是链接器找不到的函数或变量。
在您的情况下，例如，您声明并使用void get_target();，但没有定义，只有void get_target(string& key) {...}。您必须声明原型与定义相同。
也许你的意思是：
// declare prototype
void get_target(string& key);
// define function
void get_target(string& key)
{
cout << "What part number should I search for?" << endl;
cin >> key;
}
// use function
std::string key;
get_target(key);
此外，声明了swapper但未定义（在您发布的代码中）。