How to Use Cout ≪≪ Myclass

Using cin and cout to populate fields of a class C++

The compiler fails to see the operator overloads in your main.cpp translation unit, because the overloads are not found in that file, nor are they found in any of the #include files. You need to declare both overloads in your MyClass.h file instead, after the MyClass declaration:

MyClass.h:

#ifndef MyClass_h
#define MyClass_h

#include <iostream>
#include <stdio.h>
#include <string>

using namespace std;

class MyClass {
public:
    string input
    void ReadFrom(istream &is);
    void WriteTo(ostream &os) const;
};

istream& operator >>(istream &is, MyClass &cls);    
ostream& operator <<(ostream &os, const MyClass &cls);

#endif /* MyClass_h */

You can leave the definitions as-is in your MyClass.cpp file.

How to your own C++ cout like object

I'm not sure if I interpretted your question correctly but I think you want a class with an overloaded operator<< so that's what i have here

class MyClass {
  public:
    MyClass() = default;
    MyClass& operator<<(int input) {
      //do something with input
      return *this;
    }
}

You would use it like this;

MyClass myObject;
myObject << 42;
//the function would have been called

cout a function of a class

You did not define the operator << for your class Complex. So the compiler does not know how to output an object of the class.

You could define it for example the following way

std::ostream & operator <<( std::ostream &os, const Complex &c )
{
    return os << "{ " << c.GetRe() << ", " << c.GetIm() << "i }";
}

To do this the member functions GetRe and GetIm shall be declared with the qualifier const. For example

float GetRe() const
{
    return Re;
}

float GetIm() const
{
    return Im;
}

After that you can write

std::cout << z1.add(z2) << '\n'; 

Pay attention to that the member function add also should be declared like

Complex add( const Complex &s2 ) const 
{
    Complex sum(Re + s2.Re, Im + s2.Im);
    return sum;
}

Or just

Complex add( const Complex &s2 ) const 
{
    return { Re + s2.Re, Im + s2.Im };
}

Passing data types to C++ class contructor

Not commenting on whether you could use vector instead of int *my_dynamic_array, I just translated your code into a template. Hope it helps somehow:

template<typename T>
class ImageClass {
public:
    ImageClass<T>() {
        cout << "Please enter the size of array: ";
        cin >> this->size;

        my_dynamic_array = new T[this->size];
        SetPrivate();
    }

    void SetPrivate() {
        cout << "\n\nPlease enter " << this->size << " numbers for the array elements...";
        for (int i = 0; i < this->size; i++) {
            cout << "\n\n#" <<i+1<<" : ";
            cin >> my_dynamic_array[i];

        }
    }
protected:
    int size;
    T *my_dynamic_array;

};

int main() {

    ImageClass<int> ic_i;
    ImageClass<double> ic_d;
}

C++ : &(std::cout) as template argument

This fixes your code, omit the parenthesis:

#include <iostream>

template<std::ostream* stream>
class MyClass
{
public:
    void disp(void) { 
        (*stream) << "hello"; 
    }
};

int main(void)
{
    MyClass<&std::cout> MyObj;
    MyObj.disp();

    return 0;
}

Live Demo

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A more detailed explanation why can be found here:

Error with address of parenthesized member function

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