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我检查了所有文件之间的连接，以及类和函数定义，但每次我尝试运行我的程序时，它都会阻止我，并告诉我它有1个未解决的问题外部对象”。“1 unresolved externals”C++
该程序应该打开多个文件（一个“学生”文件和一个“成绩”文件），从它们读取，然后使用“查询文件”来查看数据，找到学生问在查询文件中，并将其打印到新文件中。混乱？是。
尽管如此，我非常接近解决方案，但因为我使用的是Visual Studio，它甚至不会让我运行该程序，直到找到并终止“1个未解析的外部”。它甚至不会告诉我错误在哪里。我对C++相当陌生，无论我多么努力搜索，似乎都无法解决这个问题。
这是我的主要程序：
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <fstream>
#include "Student.h"
using namespace std;
int main(){
//Request a file to read from, and open it (I haven't declared the files yet, don't worry about that)
ifstream input_file;
string studentfile = "";
string gradefile = "";
string queryfile = "";
//Create a Map for the Students
map<string, Student *> student_map;
//Open the Student file and load it in
cout << "Loading \"" << studentfile << "\"... " <<endl;
input_file.open(studentfile);
//Look for:
string id_number;
string name;
string address;
string phone;
//Boolean value to check for duplicate students
bool duplicate = false;
//Check to see if the Student File is empty
if (!input_file.eof()){
while (input_file.good()){
//Get the ID Number
input_file.get();
getline (input_file, id_number);
//Sort through and make sure there are no duplicate students
for (map<string, Student *>::iterator counter = student_map.begin(); counter != student_map.end(); counter ++){
if (counter->first == id_number){
duplicate = true;
counter = student_map.end();
}
}
if (duplicate != true){
//Get the name
input_file.get();
getline (input_file, name);
//Get the Address
input_file.get();
getline (input_file, address);
//Get the Phone Number
input_file.get();
getline (input_file, phone);
//Create a new student
Student * newStudent = new Student (id_number, name, address, phone);
//Add it to the map (referenced by the ID number)
student_map[id_number] = newStudent;
}
}
}
else {
return 0;
}
input_file.close();
//Open the Grades file and load it in
cout << "Loading \"" << gradefile << "\"... " <<endl;
input_file.open(gradefile);
//Look for (id_number already defined):
string course;
string grade;
if (!input_file.eof()){
while (input_file >> course >> id_number >> grade){
//Find the student referenced
Student* current_student = student_map[id_number];
//Calculate their grade points and add them to their grade point vector
current_student ->add_grade_points(current_student ->check_grade_points(grade));
}
}
else {
return 0;
}
input_file.close();
//Open the Query file and load it in
cout << "Loading \"" << queryfile << "\"... " << endl;
input_file.open(queryfile);
if (!input_file.eof()){
//Write to
ofstream output_file ("report.txt");
//No need to "Look for" anything, id_number alread defined
//If the file is open, write to it
if (output_file.is_open())
{
while (input_file >> id_number)
{
//Print the ID Number (With four spaces)
output_file << id_number << " ";
//Print out the GPA (With four spaces)
Student* current_student = student_map[id_number];
output_file << current_student->get_gpa() << " ";
//Print out the student's name (Then end that line)
output_file << current_student->get_name() << endl;
}
}
input_file.close();
output_file.close();
}
else {
return 0;
}
cout << endl;
cout << "File Printed.";
return 0;
}
这里是我的 “学生” 类（头文件）：
#pragma once
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <fstream>
#include <map>
using namespace std;
class Student
{
public:
Student (string _id_number, string _name, string _address, string _phone);
void add_grade_points (double grade_points);
double check_grade_points (string grade);
double get_gpa() const;
string get_name() const;
private:
string id_number;
string name;
string address;
string phone;
vector <double> grade_points;
};
最后，我的类函数：
#include "Student.h"
Student::Student (string _id_number, string _name, string _address, string _phone){
id_number = _id_number;
name = _name;
address = _address;
phone = _phone;
}
void Student::add_grade_points (double new_grade_point){
grade_points.push_back(new_grade_point);
}
double Student::check_grade_points (string grade) {
if (grade == "A")
return 4.0;
else if (grade == "A-")
return 3.7;
else if (grade == "B+")
return 3.4;
else if (grade == "B")
return 3.0;
else if (grade == "B-")
return 2.7;
else if (grade == "C+")
return 2.4;
else if (grade == "C")
return 2.0;
else if (grade == "C-")
return 1.7;
else if (grade == "D+")
return 1.4;
else if (grade == "D")
return 1.0;
else if (grade == "D-")
return 0.7;
else
return 0.0;
}
double Student::get_gpa() const{
//Add up all of the grade points
double total = 0;
for (int i = 0; i < grade_points.size(); i++) {
total = total + grade_points[i];
}
//Calculate the Grade Point Average
double gpa = total/grade_points.size();
return gpa;
}
string Student::get_name() const{
return name;
}
任何帮助会非常棒！
编辑：下面是出现错误信息：这是一个链接错误
1>MSVCRTD.lib(crtexew.obj) : error LNK2019: unresolved external symbol [email protected] referenced in function ___tmainCRTStartup
1>C:\Users\Student\Documents\Visual Studio 2010\Projects\CS235 Project 1\Debug\CS235 Project 1.exe : fatal error LNK1120: 1 unresolved externals
哪个功能没有解决？换句话说，**你得到了什么确切的错误信息？ –
我想你正试图编译控制台应用程序作为Windows GUI应用程序。 Linker预计'WinMain'，而不是'main'。检查你的项目设置。 – lapk