LNK2019 error

[GL1Rko23]

Now I know what this error means but I am having the strangest problem with it and someone else on here might have had it before and can see what I can not.

 //Counting_Observer.h
     
    #ifndef COUNTING_OBSERVER_H
    #define COUNTING_OBSERVER_H
     
    #include "observer.h"
    #include "observable.h"
    #include "monitor.h"
    #include <iostream>
     
    class CountingObserver : public Observer
    {
    public:
            CountingObserver(Observable* subject);
			//CountingObserver();
            void update(Observable* subject);
            void show_data();
    private:
            char observer_state;
    };
     
     
    #endif 

With the default constructor commented out it calls for the default constructor, but when i implement it, it then has linker errors.

#include "monitor.h"
#include "counting_observer.h"
#include "accumulating_observer.h"
#include <iostream>
using namespace std;
//==============================================================================
void process_input(char chr);

//==============================================================================
int main()
{
    // Monitor for uppercase chars
    UpperCaseMonitor     uc_monitor;
    
    // Want to be notified when there's an upper case char
    CountingObserver     observer1;
    AccumulatingObserver observer2;

    // Get registered
    uc_monitor.attach(&observer1);
    uc_monitor.attach(&observer2);

    // Prompt
    cout << "Enter some text, type ^d when done.\n";

    // Process text
    char chr;
    while (cin.get(chr))
    {
        uc_monitor.watch(chr);
        process_input(chr);
    }

    // See what observers know
    observer1.show_data();
    observer2.show_data();

	
}

Any ideas?

[Disch]

I don't remember exactly what LNK2019 is, but if it's "unresolved external symbol" that means you never gave the function a body.

[TheIdeasMan]

Linker errors mean that the linker cannot find a function definition.

This might be because you have not written the code for a function, or haven't linked a necessary library.

It can also happen if a file wasn't compiled, because it wasn't in the list of files for the project - so make misses out on that file.

If you post the full output (always do this), then we might be able to tell which is the offending function.

HTH

[GL1Rko23]

Thanks for your help guys, what I had done was defined one of the functions in the wrong header