Initializing an object as in a vector class [closed] - c++

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So, I know a vector object can be declared and initialized like this:
// Nothing new here. I know <int> is a template
// and how to implement it:
vector <int> vect{ 10, 20, 30 };
I assume that the vector object has inside an array of values, and the functions of that class (like push_back() for example) manage it. I would like and have been trying to implement something like that in a class of my own, without success. Would be interesting being able to understand how it's done! Did many "experiments" but none worked.
// Random named class:
class A_Class
{
private:
// A pointer for the type I want:
int *A_pointer_To_int;
public:
// Trying to accept the input values between
// brackets and putting them inside a temp array:
A_Class(int Input_Array[]) {}
};
int main()
{
// trying to create the object like in the vector class.
// Returns error "No instance of constructor matches the argument list":
A_Class My_Object{1,2,3}
return 0;
}

Answer 1

In a function parameter, int Input_Array[] is just syntax sugar for a decayed pointer int* Input_Array, which does not provide any information about any array that may be passed in to it.
For what you are attempting, you need to accept a std::initializer_list instead, eg:
#include <initializer_list>
#include <algorithm>
// Random named class:
class A_Class
{
private:
// A pointer for the type I want:
int *A_pointer_To_int;
// the number of values in the array:
size_t size;
public:
A_Class(std::initializer_list<int> Input_Values) {
size = Input_Values.size();
A_pointer_To_int = new int[size];
std::copy(Input_Values.begin(), Input_Values.end(), A_pointer_To_int);
}
~A_Class() {
delete[] A_pointer_To_int;
}
};
int main()
{
A_Class My_Object{1,2,3}; // works now
return 0;
}
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