重载[]和，c ++ 11

Question

So suppose we have this expression

auto x =Object.operator[][1,2,3,4];

I want my C++ code to insert the numbers 1 2 3 4 to a vector that is located inside the object my code is below.

class Object{
    Object operator[](int temp){
        this->x.push_back(temp);
        return *this;
    }
    vector<int> x;
};
int main()
{
    auto x =Object().operator[][1,2,3,4];

   return 0;
}

This code doesnt compile. As far as i have understood i have to overload comma and [] but i cant figure out how to do this.I am new to C++.

Edit extra question.!!!!!!!!!!!!!!!!!!!!!!!!!!

Check code below that is my update.

#include <iostream>

using namespace std;
class List{
    public:
    List(){}
    List(int a){
        x.push_back(a);
    }
    ~List(){}
    int operator[](int a){

        return a;
    }
        const char* operator[](const char * a){
        return a;
    }

    vector <int> x;
};
int main()
{
    List x = List{}[1,2,3,4];


   return 0;
}

Thanks to you guys i am close to the answer i am searching.How can i add all the values included in [] to some vector for example and send it to list and add to its vector.There comma operator will be overloaded but i dont know how.As far as i know and i can understand is that i have to put an object before 1 and the overloaded comma will be called but i cannot do that.is there any other special syntax that would call it.

Answer 1

A possible, straight-forward way to do this without comma overloading would be:

class Object
{
public:
    template<typename Numbers = std::initializer_list<int>>
    Object &operator[](const Numbers &numbers)
    {
        std::copy(std::begin(numbers), std::end(numbers), std::back_inserter(x_));
        return *this;
    }

private:
    std::vector<int> x_;
};
int main()
{
    Object object;
    auto &obj = object[{1,2,3,4}];
    std::vector<int> numbers = {1, 2, 3, 4};
    obj = obj[numbers];
    return 0;
}

Some noteworthy changes:

• class member visibility
• operator[] is more generic and returns a reference
• caller accepts by reference

Answer 2

I understand that you want to use the [] operator in C++ to insert a list of numbers to your object's vector.

If that's the case, you can make use of C++11's implicit conversion. Here's a sample code:

class Object
{

public:

    Object operator[]( vector<int> vx )
    {
        v.insert( v.end(), vx.begin(), vx.end() );
        return *this;
    }

private:

    vector<int> v;
};

This way you can use:

Object o;
o[{1, 2, 5}];

to insert the list "1, 2, 5" to your object's vector easily. The {1, 2, 5} will be implicitly converted to a vector of integers and your custom [] operator function will be called and executed.

Answer 3

The operator[](int) is a binary operator. It can't be overloaded to take more then 1 index argument.

here some working example:

#include <iostream>
#include <vector>

using namespace std;

class Object{
  public:
    Object operator[](int temp){
        this->x.push_back(temp);
        return *this;
    }
    vector<int> x;
};

int main() {

    auto x = Object();
    x[1];
    x[2];
    x[3];

   return 0;
}