Below I have attempted to write a sudo code for the Observer pattern when observers wish to observe different items.
Ignore the syntax errors. I wish to know if this is the correct way to implement this. If not, please suggest better ways.
Code:
// Used by the subject for keeping a track of what items the observer wants to observe
typedef struct observerListStruct
{
bool getTemperatureUpdate;
bool getHumidityUpdate;
bool getPressureUpdate;
observer's-function pointer's address;
};
// Subject's class
class weatherData
{
public:
// Observers will call this function to register themselves. The function pointer will point to the function which will get called when updates are available.
void registerObservers (observer obj, observer's-FunctionPointer)
{
// This observer's function returns which items to observe.
char* f = obj.returnItemsToObserve ();
if f[0] = `1`
observerListStruct.getTemperatureUpdate = true;
}
void unregisterObservers (observer obj) {}
private:
vector <observerListStruct> observerList;
float temperature;
float humidity;
float pressure;
void notifyObservers (){}
float getTemperature (){}
float getHumidity () {}
float getPressure () {}
} weatherDataObject;
// Base class for observers containing common functions
class observers
{
char ItemsToObserve [3] = {1, 2, 3};
// This observer's function returns which items to observe. Default - return all items
virtual char* returnItemsToObserve ()
{
return ItemsToObserve;
}
};
class observerDisplayElementCurrentConditions : public observers
{
char ItemsToObserve [3] = {1, 2};
char* returnItemsToObserve ()
{
return ItemsToObserve;
}
// this function will be used as a function pointer for getting updates
void getUpdatesAndDisplayWeatherData (float, float) {}
};
-EDIT-
Another way can be to implement a global table which'll contain the following:
Code:
Observer | Item to be observed | Function pointer addresss
Observer will fill up this table, and subject will read from the table and act accordingly?
Which one is the better way out, and why?