我创建了一个函数，它应该从.txt文件中读取信息，将其存储在一个类对象中，然后存储在一个哈希表中。我测试了信息的读取，它工作正常。当我尝试将信息存储在对象中或将对象存储在哈希表中时，会出现问题。该功能的代码如下所示：
#include<iostream>
#include<fstream>
#include<string>
#include <sstream>
#include <unordered_map>
#include "car.h"
using namespace std;
unordered_map <string, car> allCars;
void readInput()
{
int arr[24];
int x = 0;
int numberofCases,milemarker;
string line,datetime,enterexit,license;
ifstream File;
File.open("input.txt");
File >> numberofCases;
while (x <= numberofCases)
{
for (int i = 0; i < 24; i++)
{
File >> arr[i];
}
getline(File, line);
while (getline(File, line))
{
if (line.empty())
{
x++;
for (int i = 0; i < 24; i++)
{
File >> arr[i];
}
for (int i = 0; i < 24; i++)
{
cout << arr[i] << " ";
}
cout << endl;
getline(File, line);
getline(File, line);
stringstream lineStream(line);
lineStream >> license >> datetime >> enterexit >> milemarker;
string sub = datetime.substr(6, 2);
int hour = stoi(sub);
if (allCars.count(license))
{
(allCars[license]).settollCost(arr[hour]);
if (enterexit == "enter")
{
(allCars[license]).setcarEnter(milemarker);
}
else if (enterexit == "exit")
{
(allCars[license]).setcarExit(milemarker);
(allCars[license]).calculateMiles;
(allCars[license]).calculateBill; // calculates bill for trip
(allCars[license]).printInfo;
}
}
else if (!allCars.count(license))
{
car car1(license);
allCars[license] = car1;
}
cout << license << endl << datetime << endl << enterexit << endl << milemarker << endl << hour << endl;
}
else
{
stringstream lineStream(line);
lineStream >> license >> datetime >> enterexit >> milemarker;
string sub = datetime.substr(6, 2);
int hour = stoi(sub);
if (allCars.count(license))
{
(allCars[license]).settollCost(arr[hour]);
if (enterexit == "enter")
{
(allCars[license]).setcarEnter(milemarker);
}
else if (enterexit == "exit")
{
(allCars[license]).setcarExit(milemarker);
(allCars[license]).calculateMiles;
(allCars[license]).calculateBill; // calculates bill for trip
(allCars[license]).printInfo;
}
}
else if (!allCars.count(license))
{
car car1(license);
allCars[license] = car1;
}
cout << license << endl << datetime << endl << enterexit << endl << milemarker << endl << hour << endl;
for (int i = 0; i < 24; i++)
{
cout << arr[i] << " ";
}
cout << endl;
}
}
}
}
我从构建中获得的输出如下：
c:\program files (x86)\microsoft visual studio 12.0\vc\include\tuple(746): error C2512: 'car' : no appropriate default constructor available
1> c:\program files (x86)\microsoft visual studio 12.0\vc\include\tuple(762) : see reference to function template instantiation 'std::pair<const _Kty,_Ty>::pair<std::tuple<const std::basic_string<char,std::char_traits<char>,std::allocator<char>> &>,std::tuple<>,0,>(_Tuple1 &,_Tuple2 &,std::_Arg_idx<0>,std::_Arg_idx<>)' being compiled
1> with
1> [
1> _Kty=std::string
1> , _Ty=car
1> , _Tuple1=std::tuple<const std::basic_string<char,std::char_traits<char>,std::allocator<char>> &>
1> , _Tuple2=std::tuple<>
1> ]
1> c:\program files (x86)\microsoft visual studio 12.0\vc\include\tuple(762) : see reference to function template instantiation 'std::pair<const _Kty,_Ty>::pair<std::tuple<const std::basic_string<char,std::char_traits<char>,std::allocator<char>> &>,std::tuple<>,0,>(_Tuple1 &,_Tuple2 &,std::_Arg_idx<0>,std::_Arg_idx<>)' being compiled
1> with
1> [
1> _Kty=std::string
1> , _Ty=car
1> , _Tuple1=std::tuple<const std::basic_string<char,std::char_traits<char>,std::allocator<char>> &>
1> , _Tuple2=std::tuple<>
1> ]
1> c:\program files (x86)\microsoft visual studio 12.0\vc\include\xmemory0(600) : see reference to function template instantiation 'std::pair<const _Kty,_Ty>::pair<const std::basic_string<char,std::char_traits<char>,std::allocator<char>>&,>(std::piecewise_construct_t,std::tuple<const std::basic_string<char,std::char_traits<char>,std::allocator<char>> &>,std::tuple<>)' being compiled
1> with
1> [
1> _Kty=std::string
1> , _Ty=car
1> ]
1> c:\program files (x86)\microsoft visual studio 12.0\vc\include\xmemory0(600) : see reference to function template instantiation 'std::pair<const _Kty,_Ty>::pair<const std::basic_string<char,std::char_traits<char>,std::allocator<char>>&,>(std::piecewise_construct_t,std::tuple<const std::basic_string<char,std::char_traits<char>,std::allocator<char>> &>,std::tuple<>)' being compiled
1> with
1> [
1> _Kty=std::string
1> , _Ty=car
1> ]
1> c:\program files (x86)\microsoft visual studio 12.0\vc\include\xmemory0(723) : see reference to function template instantiation 'void std::allocator<_Other>::construct<_Objty,const std::piecewise_construct_t&,_Ty,std::tuple<>>(_Objty *,const std::piecewise_construct_t &,_Ty &&,std::tuple<> &&)' being compiled
1> with
1> [
1> _Other=std::_List_node<std::pair<const std::string,car>,void *>
1> , _Objty=std::pair<const std::string,car>
1> , _Ty=std::tuple<const std::basic_string<char,std::char_traits<char>,std::allocator<char>> &>
1> ]
整个输出实际上更长，但几乎所有输出都与上面公布的相同。我不知道这意味着什么或我究竟做错了什么，所以任何澄清将不胜感激。如果您需要更多信息，例如类定义或头文件，我可以提供;只是不想超载这个问题。
答案 0 :(得分：1)
正如Nemo所说，你很可能没有car班的默认构造函数which the operator[] of unordered_map requires。
您需要制作默认构造函数，或者使用insert和find代替。