How to overload assignment operator inside a class?

[CJha]

Hi! I have a struct that has two members and I want to assign the current value of newState to oldState before changing the value of newState and then emit a signal with the new state as a parameter. My struct looks like this:

/* myData.h */
enum class myState_Enum{Uninitialized, OFF, ON, Processing};
struct myStruct
{
    myState_Enum oldState,
    myState_Enum newState,
};

The only way I am currently able to override the assignment operator is like this:

/* myData.h */
enum class myState_Enum{Uninitialized, OFF, ON, Processing};
struct myStruct
{
    myState_Enum oldState,
    myState_Enum newState,
    myStruct &operator=(myStruct val)
    {
        //perform the assignment here
        return *this;
    }
};

But, it defeats the purpose of overloading the assignment operator for me. I want to overload this in my class where this struct is a member so that I can emit a signal each time the newState is changed. I want to do something like this:

/* mainData.h */
class mainData
{
public:
    mainData();
    myStruct State;
    void operator=(myState_Enum val);

signals:
    void stateChanged(myState_Enum val);
}


/*mainData.cpp */
mainData::mainData()
{
    State.oldState = myState_Enum::Uninitialized;
    State.newState = myState_Enum::Uninitialized;
}

void mainData::operator=(myState_Enum val)
{
    State.oldState = State.newState;
    State.newState = val;
    emit stateChanged(val);
}

Is there any way I can achieve this? Thanks :)

[SGaist]

Hi,

Not directly as you want. The usual way is to have a setter that does the value check and emit the signal if appropriate.

Emitting a signal requires the class to derive from QObject which is not copyable.

[CJha]

@SGaist Thank you :)