Using virtual methods with Arduino - c++

Question

I have a small piece of Arduino code that gives me compilation error:
error: no matching function for call to 'PushButton::PushButton(int, LeftButtonEvent*)
In its own header file I have two classes:
class Event
{
public:
virtual void handle() {
}
};
class PushButton
{
public:
PushButton(int pinButton, Event *event);
uint8_t read();
private:
uint8_t _buttonState;
Event _event;
};
And the source file for classes:
PushButton::PushButton(int pinButton, Event *event)
{
// implementation
}
uint8_t PushButton::read() {
// implementation
return _buttonState;
}
In the main ino sketch header file I have defined a new class that extends Event class:
class LeftButtonEvent : public Event {
public:
virtual void handle();
};
And in the sketch source file I provide the implementation for the handle method and use it:
void LeftButtonEvent::handle() {
log("Is working!!!!!");
}
LeftButtonEvent leftButtonEvent;
PushButton leftButton;
void setup() {
leftButton = PushButton(PIN_LEFT_BUTTON, &leftButtonEvent);
}
I was expecting the constructor for PushButton to accept a LeftButtonEvent type because it extends Event class, but it looks like it doesn't like it.
Am I missing something?

Answer 1

As there is only incomplete code and I couldn't test it directly, there is example how it's possible to get it work (it's all in one sketch, Arduino IDE 1.6.12, C++11):
class Event {
public:
virtual void handle() = 0;
};
class EventLeft : public Event {
public:
virtual void handle() {
Serial.println("EventLeft");
}
} leftEvent;
class EventRight : public Event {
public:
virtual void handle() {
Serial.println("EventRight");
}
} rightEvent;
class PushButton {
public:
PushButton(int8_t _pin, Event * _event) : pin(_pin), state(true), event(_event) {
pinMode(pin, INPUT_PULLUP);
}
void check() {
if (! digitalRead(pin)) { // inverted logic
if (state) event->handle();
state = false;
} else {
state = true;
}
}
private:
int8_t pin;
bool state;
Event * event;
};
PushButton buttons[] = {
{4, &leftEvent},
{5, &rightEvent}
};
void setup() {
Serial.begin(115200);
}
void loop() {
delay(10);
for (PushButton & button : buttons) button.check();
//// if the range based for loop above doesn't work, you have to use old school one:
// for (uint8_t i = 0; i < 2; ++i) buttons[i].check();
}