ERROR C2039: 'vector': is not a member of 'std' - c++

Question

I am new to C++ and I am trying to make a little dungeon crawler game. Currently I have multiple vectors declared in my header files but they seem to give multiple errors. I have tried searching for this problem on StackOverflow but the answers don't really seem to work.
Here is one of my header files: (Hero.h)
#pragma once
class Hero {
public:
Hero();
std::string name;
int experience;
int neededExperience;
int health;
int strength;
int level;
int speed;
std::vector<Item> items = std::vector<Item>();
void levelUp();
private:
};
Here is my .cpp file: (Hero.cpp)
#include "stdafx.h"
#include <vector>
#include "Hero.h"
#include "Item.h"
Hero::Hero() {
}
void Hero::levelUp()
{
};
Like I said I am new to C++ so there might be a lot more wrong with my code than I know. This is just a test.
Below are the errors that are shown in the Error list of Visual Studio 2015:
Error C2039 'vector': is not a member of 'std' CPPAssessment hero.h 13
Error C2143 syntax error: missing ';' before '<' CPPAssessment hero.h 13
Error C4430 missing type specifier - int assumed. Note: C++ does not support default-int CPPAssessment hero.h 13
Error C2238 unexpected token(s) preceding ';' hero.h 13

Answer 1

Include <vector> in your Hero.h header and consider removing it from your Hero.cpp file as mentioned in the comments below.

Answer 2

std::vector<Item> items = std::vector<Item>(); declares a complete type.
Therefore the compiler needs to know the declaration of std::vector at that point (amongst other things, it's required to establish the compile-time evaluable constant sizeof Hero). The solution is to #include <vector> in the header hero.h, not the source file.

Answer 3

//.h
template<class _Ty>
class std::allocator;
template<class _Ty, class _Alloc = std::allocator<_Ty> >
class std::vector;
//this line in .cpp file. Put it before custom header files.
#include<vector>
Tested in vs 2017.
In this way, no header file included in your custom header file.
But not sure why the save way for stack does not work.
For further information, https://github.com/YagaoDirac/snippet-set-for-cpp. And a discord link inside.