包含类对象的向量在主方法中引发错误
Vector containing class objects throwing errors in main method
我正在用如下所示的主方法生成Student类型的向量，这是我编写的一个类：
int main() {
ifstream prefile("File.csv");
string l;
vector<Student> students;
while(getline(prefile, l)) {
istringstream ss(l);
string token;
string * lineArr = new string[12];
int temp = 0;
while(getline(ss, token, ',')) {
lineArr[temp] = token;
temp++;
}
Student s(lineArr[0], lineArr[1]);
for (int i = 2; i < 12; i++) {
s.addScore(atoi(lineArr[i].c_str()));
}
students.push_back(s);
delete [] lineArr;
}
sort(students.begin(), students.end(), compareStudents);
for (int i = 0; i < students.size(); i++) {
students.at(i).print();;
}
prefile.close();
return 0;
}
主要方法是从File.csv中读取并创建一个学生向量，每个学生都有名字、姓氏和10分。这是我的Student类供参考：
class Student {
string last;
string first;
vector<int> scores;
public:
Student():last(""), first("") {}
Student(string l, string f) {
last = l;
first = f;
}
~Student() {
last = "";
first = "";
}
Student(Student& s) {
last = s.last;
first = s.first;
scores = s.scores;
}
Student& operator = (Student& s) {
last = s.last;
first = s.first;
scores = s.scores;
return *this;
}
void addScore(int n) {
scores.push_back(n);
}
void print() {
cout << first << " " << last << ":" << endl;
cout << scores[0];
for (int i = 1; i < scores.size(); i++) {
cout << ", " << scores[i];
}
cout << endl;
}
};
出于某种原因，我遇到了一些我无法理解的奇怪错误：
In file included from /Users/.../Desktop/stl/main.cpp:3:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/iostream:38:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/ios:216:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/__locale:15:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/string:439:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/algorithm:628:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:1466:36: error: no matching constructor for initialization of 'Student'
::new ((void*)__p) _Tp(__a0);
^ ~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/vector:1582:25: note: in instantiation of function template specialization 'std::__1::allocator_traits<std::__1::allocator<Student> >::construct<Student, Student>' requested here
__alloc_traits::construct(this->__alloc(),
^
/Users/.../Desktop/stl/main.cpp:74:13: note: in instantiation of member function 'std::__1::vector<Student, std::__1::allocator<Student> >::push_back' requested here
students.push_back(s);
^
/Users/.../Desktop/stl/main.cpp:27:3: note: candidate constructor not viable: 1st argument ('const Student') would lose const qualifier
Student(Student& s) {
^
/Users/.../Desktop/stl/main.cpp:18:3: note: candidate constructor not viable: requires 0 arguments, but 1 was provided
Student():last(""), first("") {}
^
/Users/.../Desktop/stl/main.cpp:19:3: note: candidate constructor not viable: requires 2 arguments, but 1 was provided
Student(string l, string f) {
^
In file included from /Users/.../Desktop/stl/main.cpp:5:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/vector:1569:21: error: no matching member function for call to 'construct'
__alloc_traits::construct(__a, _VSTD::__to_raw_pointer(__v.__end_), _VSTD::forward<_Up>(__x));
~~~~~~~~~~~~~~~~^~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/vector:1587:9: note: in instantiation of function template specialization 'std::__1::vector<Student, std::__1::allocator<Student> >::__push_back_slow_path<const Student>' requested here
__push_back_slow_path(__x);
^
/Users/.../Desktop/stl/main.cpp:74:13: note: in instantiation of member function 'std::__1::vector<Student, std::__1::allocator<Student> >::push_back' requested here
students.push_back(s);
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:1464:21: note: candidate template ignored: substitution failure [with _Tp = Student, _A0 = Student]
static void construct(allocator_type& __a, _Tp* __p, const _A0& __a0)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:1458:21: note: candidate function template not viable: requires 2 arguments, but 3 were provided
static void construct(allocator_type& __a, _Tp* __p)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:1470:21: note: candidate function template not viable: requires 4 arguments, but 3 were provided
static void construct(allocator_type& __a, _Tp* __p, const _A0& __a0,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:1477:21: note: candidate function template not viable: requires 5 arguments, but 3 were provided
static void construct(allocator_type& __a, _Tp* __p, const _A0& __a0,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:1535:17: error: no matching function for call to 'construct'
construct(__a, _VSTD::__to_raw_pointer(__end2-1), _VSTD::move_if_noexcept(*--__end1));
^~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/vector:874:21: note: in instantiation of function template specialization 'std::__1::allocator_traits<std::__1::allocator<Student> >::__construct_backward<Student *>' requested here
__alloc_traits::__construct_backward(this->__alloc(), this->__begin_, this->__end_, __v.__begin_);
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/vector:1571:5: note: in instantiation of member function 'std::__1::vector<Student, std::__1::allocator<Student> >::__swap_out_circular_buffer' requested here
__swap_out_circular_buffer(__v);
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/vector:1587:9: note: in instantiation of function template specialization 'std::__1::vector<Student, std::__1::allocator<Student> >::__push_back_slow_path<const Student>' requested here
__push_back_slow_path(__x);
^
/Users/.../Desktop/stl/main.cpp:74:13: note: in instantiation of member function 'std::__1::vector<Student, std::__1::allocator<Student> >::push_back' requested here
students.push_back(s);
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:1464:21: note: candidate template ignored: substitution failure [with _Tp = Student, _A0 = Student]
static void construct(allocator_type& __a, _Tp* __p, const _A0& __a0)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:1470:21: note: candidate function template not viable: requires 4 arguments, but 3 were provided
static void construct(allocator_type& __a, _Tp* __p, const _A0& __a0,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:1477:21: note: candidate function template not viable: requires 5 arguments, but 3 were provided
static void construct(allocator_type& __a, _Tp* __p, const _A0& __a0,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:1458:21: note: candidate function template not viable: requires 2 arguments, but 3 were provided
static void construct(allocator_type& __a, _Tp* __p)
^
3 errors generated.
任何帮助都将不胜感激，因为我不知道自己做错了什么。
Student(Student& s) {
应该是
Student(const Student& s) {
和
Student& operator = (Student& s) {
应该是
Student& operator = (const Student& s) {
除非您用const参数声明您的赋值运算符和复制构造函数，否则其他代码将很难复制您的对象。这正是这里发生的情况，std::vector类无法复制Student对象，因此会出现编译器错误。
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