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static varible and function with <template>

leeto (37)
I try to create small project in order to better understand how key word static works with templates . However some compiles errors crush my plan. Could you help me resolve compile errors:


1>------ Build started: Project: 4.2b - Ex 1. Static Variable for Array Def Size. Templates, Configuration: Release Win32 ------
1> main.cpp
1>c:\all my\с++\ha level 6\solution level 6\solution level 6\4.2b - ex1. static variable for array def size. templates\array.cpp(40): error C2724: 'Array<Type>::DefaultSize' : 'static' should not be used on member functions defined at file scope
1> with
1> [
1> Type=int
1> ]
1> c:\all my\с++\ha level 6\solution level 6\solution level 6\4.2b - ex1. static variable for array def size. templates\array.cpp(40) : while compiling class template member function 'void Array<Type>::DefaultSize(int)'
1> with
1> [
1> Type=int
1> ]
1> main.cpp(77) : see reference to class template instantiation 'Array<Type>' being compiled
1> with
1> [
1> Type=int
1> ]
1>c:\all my\с++\ha level 6\solution level 6\solution level 6\4.2b - ex1. static variable for array def size. templates\array.cpp(32): error C2724: 'Array<Type>::DefaultSize' : 'static' should not be used on member functions defined at file scope
1> with
1> [
1> Type=int
1> ]
1> c:\all my\с++\ha level 6\solution level 6\solution level 6\4.2b - ex1. static variable for array def size. templates\array.cpp(32) : while compiling class template member function 'int Array<Type>::DefaultSize(void)'
1> with
1> [
1> Type=int
1> ]
1>c:\all my\с++\ha level 6\solution level 6\solution level 6\4.2b - ex1. static variable for array def size. templates\array.cpp(32): error C2724: 'Array<Type>::DefaultSize' : 'static' should not be used on member functions defined at file scope
1> with
1> [
1> Type=double
1> ]
1> c:\all my\с++\ha level 6\solution level 6\solution level 6\4.2b - ex1. static variable for array def size. templates\array.cpp(32) : while compiling class template member function 'int Array<Type>::DefaultSize(void)'
1> with
1> [
1> Type=double
1> ]
1> main.cpp(79) : see reference to class template instantiation 'Array<Type>' being compiled
1> with
1> [
1> Type=double
1> ]
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========


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//array.h
#ifndef Array_H
#define Array_H

template <class Type> //Remove the "=double" default parameter.
class Array
{
private:
  int m_size;
  Type* m_data; //m_data should be a pointer, since you want to allocate data to it
 // static int m_size_default;

//protected : 
	//static int m_size_default;

public:

static int m_size_default;
  Array();
  Array(int new_size);
  Array(const Array<Type>& ar);
  ~Array(); //Don't make your destructor virtual. There is no reason to do it.

  // Selectors 
  int Size() const {return m_size;};
  static int DefaultSize();
  static void DefaultSize(int newSize) ;
  const Type& Array<Type>::GetElement(int index) const;
  void Array<Type>::SetElement(const Type& type_object, int index);
  Array<Type>& operator=(const Array& ar); //Const correctness here.
  Type& Array<Type>::operator [] (int index);
  void Swap(Array& ar);  
};



#endif

// ****************

//point.h

#include "array.h"
#include <sstream>
#include <iostream>
using namespace std;


class Point
{
private:
    double m_x;                                
    double m_y;                                
public:
    // Constructors
    ... // limition of 9000 char. 
};

//*****************

//array.cpp
#include "Array.h"
#include <sstream>
#include <iostream>
#include <exception>
using namespace std;
#ifndef Array_CPP
#define Array_CPP



template<class T>
int Array<T>::m_size_default = 10;

// default constructor 
template <typename T>
Array<T>::Array()
{

m_data = new T[m_size_default];
 
// iterate through array
for(int i=0; i<m_size_default; i++)
{
T temp;
m_data[i] = temp;
}
}

template <typename T>
static int Array<T>::DefaultSize() 
{ // line 32 
	
	return m_size_default;
}


template <typename T>
  static void Array<T>::DefaultSize(int newSize) 
  { // line 40 
	  m_size_default = newSize; 
	  
  };


template <class Type>
Array<Type>::Array(int new_size) : m_size(new_size), m_data(new Type[new_size])
{ }

template <class Type>
Array<Type>::~Array()
{
  //Technically, the if is not necessary
  if(m_data)
  {
    delete[] m_data;
    m_data = 0;
  }

  //Not necessary either, but just to be clean
  m_size = 0;
}

template <class Type>
Array<Type>::Array(const Array& ar) : m_data(0), m_size(0)
{
  if(!ar.m_data) {return;}

  Array tmp; //Copy construct into another temporary array, this way, if something throws, tmp will clean itself up.

  //Create the array
  tmp.m_data = new Type[ar.m_size];
  tmp.m_size = ar.m_size;

  //Copy the array elements
  for(int i = 0; i < tmp.m_size; ++i)
    {tmp.m_data[i] = ar.m_data[i];}

  //All done! swap into this!
  this->Swap(tmp);
}

template <class Type>
Array<Type>& Array<Type>::operator=(const Array& ar)
{
  //Check self assign:
  if(this == &ar) {return *this;}

  Array<Type> copy(ar); //Create a copy of ar; If this fails, then *this will not be changed, and nothing will leak

  //Succeeded creating copy. Now we can put it inside this
  this->Swap(copy); //And then swap the copy into this!

  return *this;
}

template <class Type>
void Array<Type>::Swap(Array& ar)
{
  Type* data = m_data;
  int   size = m_size;
  m_data = ar.m_data;
  m_size = ar.m_size;
  ar.m_data = data;
  ar.m_size = size;
}

template <class Type> 
void Array<Type>::SetElement(const Type& type_object, int index)
{

		if (index >= m_size || index < 0 )
		{ throw std:: out_of_range ("out of range error in void Array<Type>::SetElement");}
		m_data[index] = type_object;
		cout << "Set Element " << type_object  << endl;

	
}
template <class Type> 
const Type& Array<Type>::GetElement(int index) const
{
	
		if (index >= m_size || index < 0)
		{ throw std::out_of_range ("Out of range error in void Array<Type>::GetElement");} 

	return m_data[index];
}
template <class Type> 
Type& Array<Type>::operator [] (int index) 
{
    cout << "Array [] operator" << endl;
 
    if (index >= this->m_size)
	{
        cout << "i am hreeeee" << endl;
        return this->m_data[0];
	}
    return m_data[index];
}



#endif //Array_CPP

// ************ 




/*
Exercise 1: Static Variable for Array Default Size (optional)

Static variables, which are shared between all instances of a class, 
behave slightly different with templates. We are going to test this with a static variable in 
the Array class that indicates the default array size when using the default constructor.
Add a static data member to the Array class indicating the default size.
Initialise this static in the source file to a value.
Also add static functions to set and get the default size.
In the default constructor, use the static default size variable 
instead of a literal value to set the array size.
Test the following code in the main program:
Code (cpp):
Array<int> intArray1;
Array<int> intArray2;
Array<double> doubleArray;
 
cout<<intArray1.DefaultSize()<<endl;
cout<<intArray2.DefaultSize()<<endl;
cout<<doubleArray.DefaultSize()<<endl;
 
intArray1.DefaultSize(15);
 
cout<<intArray1.DefaultSize()<<endl;
cout<<intArray2.DefaultSize()<<endl;
cout<<doubleArray.DefaultSize()<<endl;
What values are printed? Can you explain the result?
*/
//
//
// QuantNet C++ course
// LEVEL 6. 4.2b - Advanced Templates
// https://www.quantnet.com/threads/level-6-homework.7857/
// Exercise 1: Static Variable for Array Default Size (optional)
//
// Created by Denis Igoshev
//
// additional helping links: 
// https://www.quantnet.com/threads/4-2b-exercise-1.9082/
// 

//main.cpp
		#include "point.h"
		#include <iostream>
		#include "array.cpp"
		#include <exception>
		using namespace std;

int main()
{
	Array<int> intArray1;
    Array<int> intArray2;
    Array<double> doubleArray;
 
    cout<<intArray1.DefaultSize()<<endl;
    cout<<intArray2.DefaultSize()<<endl;
    cout<<doubleArray.DefaultSize()<<endl; // line 57 
 
    intArray1.DefaultSize(15);
   
    cout<<intArray1.DefaultSize()<<endl;
    cout<<intArray2.DefaultSize()<<endl;
    cout<<doubleArray.DefaultSize()<<endl;
	
}


many thanks in advance
closed account (o3hC5Di1)
Hi there,

Not 100% sure about this, but I think this error:
1>c:\all my\с++\ha level 6\solution level 6\solution level 6\4.2b - ex1. static variable for array def size. templates\array.cpp(40): 
error C2724: 'Array<Type>::DefaultSize' : 'static' should not be used on member functions defined at file scope


Is because you are not declaring DefaultSize as a method of a class, but on a global scope level.
Try removing the static keyword in its declaration (array.cpp line 29 and 37) and see if that works.

Hope that helps.

All the best,
NwN
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