Question

I am refactoring some code to decouple GUI from some state.

#include <StateObject>

Class GUI{  
 ...  
 StateObject A;
 void doSomething() { A->hullaballoo();}  

 **void ReFreshMyGui() { //take state A and redraw }**  
 };  

State object is being shared by multiple classes to update the state but this Gui Object specializes in displaying the state. So I would like to call the Refresh function via StateObject whenever its modified.

I am not sure how or if signals will provide the solution. Any hints?

Answer 1

In order to decouple GUI and Data you could use the MVC pattern. This means your GUI should register to your model’s (data) object(s) and whenever the data changes the GUI will be notified and it will be the GUI to redraw itself.

But careful, the model should not have the notion of a concrete GUI, instead the GUI should implement an observer interface containing a method (e.g. void Update()) that will be called whenever changes occur (notification handler).

Just look for the MVC-pattern on google. You’ll find thousands of useful tutorials.
You may also take in consideration the MVP and the MVVM patterns.

Example:

    class Observer
    {
     virtual void Update(void* data) = 0;
    }


    class GUI : public Observer
    {
public:
     virtual void Update(void* data)
     {
         //Redraw method and some other things you may 
      //want to do with the new data
     }
    }


    class Model 
    {
    private:
       int m_iData;
       List<Observer> observers;

    public:
       void SetData(int iData)
       {
           m_iData = iData;
           for(int i = 0; i < observers.Length; i++)
           {
               observers[i].Update(NULL);
           }
       }
    }