C ++如何使用模板类调用模板函数？

Question

I have a quick question for my program: How can I call this template function with Set , rather than int ? I have a class here called Set

#include <iostream>
#include <vector>

using namespace std;

template<typename T> 
class Set
{
public:
    class Iterator;
    void add(T v);
    void remove(T v);
    Iterator begin();
    Iterator end();

private:
    vector<T> data;
}; 

Here's my cpp:
Unfortunately, main cannot be a template function so I had to make another function addstuff , which main calls

template <class T>
Set<T> addstuff()
{
    Set<T> a;
    a.add(1);
    a.add(2);
    a.add(3);
    a.add("a string");

    return a;
}

void main()
{
    addstuff<Set>(); //<< Error here. If I use addstuff<int>(), it would run but   
                     //I can't add string to it. I am required to be able to add 
                     //different data types to this vector
}

Answer 1

Your writing addstuff<Set>() would be an attempt to resolve to Set<Set> addstuff() which is meaningless.

addstuff<std::string>() would allow you to add std::string s to your set, but then a.add(1) would fail since the literal cannot be implicitly converted to a string type.

addstuff<int>() does work but that's a merry coincidence. add(1) has the correct type in that instance to be added to Set<int> .

You could build a class Foo that has non-explicit constructors to a string and an integer and make that your template type: addstuff<Foo>() . But I'm not convinced that's what your professor wants you to do and there are better ways of solving this (type erasure for one, but this is getting quite involved).