C ++, Class: Out of order element error declaration?

I am trying to create a dynamic array using the class. In my header file, I have the following code:

#ifndef DYNAMICARRAY
#define DYNAMICARRAY
#include <iostream>

class Array 
{

public:

    Array(); // Constructor - Initialises the data members
    ~Array(); // Destructor - That deletes the memory allocated to the array
    void addTings (float itemValue); // which adds new items to the end of the array
    float getTings (int index); // which returns the item at the index
    void size(); // which returns the number of items currently in the array

private:

    int arraySize;
    float  *floatPointer = nullptr;
};

#endif // DYNAMICARRAY

      

        
        
        
      

    

And in my .cpp file I have the following code:

#include "DYNAMICARRAY.h"

Array::Array()
{
    floatPointer = new float[arraySize];
}

Array::~Array()
{
    delete[] floatPointer;
}

void Array::addTings (float itemValue);  // Out-of-line declaration ERROR
{
    std::cout << "How many items do you want to add to the array";
    std::cin >> arraySize;
}

float Array::getTings (int index);    // Out-of-line declaration ERROR
{

}

void Array::size()
{

}

      

        
        
        
      

    

I get the message Out-of-line member, there must be a compile-time definition error on both lines:

float Array::getTings (int index);

      

        
        
        
      

    

and

void Array::addTings (float itemValue);

      

        
        
        
      

    

Can anyone understand why? I thought I linked the header file to the cpp file correctly, but obviously not?