[英]How to implement a class that has a significantly different implementation in one case?
[英]How to implement a class that has one of either two types for an arg
如果我有一個c ++類,例如:
class Student
{
public:
string name;
int assigned_number;
};
並且我想在每個實例中使用名稱或數字,但不能同時使用兩者,是否有一種方法可以使之成為“ Or
類型,而只需要其中一個?
如果您使用的是C ++ 17或更高版本 ,則可以使用<variant>
std::variant
:
#include <iostream>
#include <variant> // For 'std::variant'
class Student
{
public:
std::variant<std::string, int> name_and_id;
};
int main() {
Student stud; // Create an instance of student
// Pass a string and print to the console...
stud.name_and_id = "Hello world!";
std::cout << std::get<std::string>(stud.name_and_id) << std::endl;
// Pass an integer and print to the console...
stud.name_and_id = 20;
std::cout << std::get<int>(stud.name_and_id) << std::endl;
}
std::variant
是C ++ 17的新增功能,旨在替換C中的並集,並且在出現錯誤的情況下具有異常...
您可以使用聯合。
#include <string>
class Student
{
// Access specifier
public:
Student()
{
}
// Data Members
union
{
std::string name;
int assigned_number;
};
~Student()
{
}
};
int main()
{
Student test;
test.assigned_number = 10;
test.name = "10";
return 0;
}
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