非静态数据成员的无效使用

我想创建一个文件，在这个文件中我可以将person添加到PersonList，其中包含一个计数器，以确保不超过PersonList的容量。我注释了所有的函数，以明确它们应该执行什么任务。

在编译过程中，我得到以下错误:

invalid use of non-static data member 'PersonList::m_Capacity'

不幸的是，我无法找出代码中的错误:

main.cpp

#include <iostream>
#include "Person.h"
#include "PersonList.h"
int main()
{
    Person p1 = Person("John", 21);
    Person p2 = Person("Elham", 19);
    PersonList p_list = PersonList();
    p_list.add(p1);
    p_list.add(p2);
    std::cout << p_list.get_Size() << std::endl;
    Person p = p_list.get(0);
    std::cout << p.get_Name() << " " << p.get_Age() << std::endl;
    return 0;
}

Person.h

#ifndef PERSON_H
#define PERSON_H
class Person
{
    public:
        Person();
        Person(std::string Name, int Age);
        void set_Name(std::string name);
        void set_Age(int age);
        std::string get_Name();
        int get_Age();
    private:
        std::string m_Name;
        int m_Age;
};
#endif // PERSON_H

Person.cpp

#include <string>
#include "Person.h"
Person::Person(){}
Person::Person(std::string Name, int Age){
// pre:  0 <= Age
// post: m_Name, if pre Name (is true) Age = m_Age,
//       otherwise age = -1
    set_Name(Name);
    if (0 <= Age){
        set_Age(Age);
    }
    else{
        set_Age(-1);
    }
}
void Person::set_Name(std::string Name){
// post: m_Name = Name
    m_Name = Name;
}
void Person::set_Age(int Age){
// pre:  0 <= Age
// post: if pre Age (is true) = m_Age, otherwise m_Age = -1;
    if (0 <= Age){
        m_Age = Age;
    }
    else set_Age(-1);
}
std::string Person::get_Name(){
// post: returns name
    return m_Name;
}
int Person::get_Age(){
// post: returns age
    return m_Age;
}

PersonList.h

#ifndef PERSONLIST_H
#define PERSONLIST_H
class PersonList
{
    public:
        PersonList();
        void add(Person p);
        void set_Size(int Size);
        int get(int index);
        int get_Size();
    private:
        const int m_Capacity;
        const Person m_Empty;
        Person m_Data[m_Capacity];
        int m_Size;
};
#endif // PERSONLIST_H

PersonList.cpp

#include "Person.h"
#include "PersonList.h"
PersonList::PersonList()
m_Capacity(10), m_Empty(Person())
{
// post: has created a new PersonList-object with
//      CAPACITY elements and size = 0
    set_Size(0);
}
void PersonList::add(Person p){
// pre:  size < CAPACITY
// post: if pre (is true) p has been stored at the
//      first empty location. size was incremented.
    if (m_Size < m_Capacity){
        m_Data[m_Size] = p;
        set_Size(m_Size+1);
    }
}
void set_Size(int Size){
    m_Size = Size;
}
int PersonList::get(int index){
// pre:  0 <= index && index < size
// post: if pre returns data[index] otherwise returns EMPTY
    if (0 <= index && index < m_Size){
        return m_Data[index];
    }
    else{
        return m_EMPTY;
    }
}
int PersonList::get_Size(){
// post returns size;
    return m_Size;
}