Structures inside private - c++

Question

I do not know how to work with structures inside a class. I think I have the first part right but nothing works in the main. When I try running my program it says "function does not take 0 arguments" Should I write everything in the main like this:
P.Read(BOX m);
Here's my code so far as below:
#include <iostream>
#include <string>
using namespace std;
template <class T, int n>
class SIX
{
private:
struct BOX
{
T a[n];
string name;
};
public:
void Read(BOX m)
{
cout<<"Enter your name: ";
cin>>m.name;
cout<<m.name<<" please enter "<<n<<" data: ";
for(int i=0;i<n;++i)
cin>>m.a[i];
}
void SortArray(BOX m)
{
sort(m.a, m.a+n);
}
void Display(BOX m)
{
cout<<m.name<<" this is the sorted list of data in your array a: ";
for(int i=0;i<n;++i)
cout<<m.a[i]<<'\t';
cout<<endl;
}
};
int main()
{
SIX <int, 6> P;
SIX <string, 5> Q;
P.Read();
P.SortArray();
P.Display();
cout<<endl;
Q.Read();
Q.SortArray();
Q.Display();
cout<<endl;
system("pause");
return 0;
}

Answer 1

No, define Read as
void Read()
{
cout<<"Enter your name: ";
cin>>BOX.name;
cout<<BOX.name<<" please enter "<<n<<" data: ";
for(int i=0;i<n;++i)
cin>>BOX.a[i];
}
Read is a member function, and it has access to Box, so that's all you have to do.
Same for the other functions, you don't need to specify BOX m as the parameter, replace it by () and replace m by BOX inside the code.
As #Barmar pointed out, your struct BOX just defines a type, you should define a member variable named BOX. Simplest way to do it is to just move BOX to the end of struct declaration,
struct
{
T a[n];
string name;
} BOX;