On value changed event.

#include <functional>

class TempWrapper
{
public:
    TempWrapper() { /*...*/ }
    TempWrapper(int val) : Value(val) { /*...*/ }

    ~TempWrapper() { /*...*/ }

    TempWrapper & operator = (int val)
    {
        Value = val;
        if (Changed) Changed(Value);
        return *this;
    }

    typedef std::function<void(int)> EvDef;
    EvDef Changed;

    int Value;
};

class UsingWrapper
{
public:

    TempWrapper MyValue;

    UsingWrapper() { /*...*/ }
    UsingWrapper(int val) : MyValue(val) { /*...*/ }

    ~UsingWrapper() { /*...*/ }
};

void onChanged(int value)
{
    printf("value changed %d\n", value);
}

int main()
{
    UsingWrapper some_value(32);

    some_value.MyValue.Changed = TempWrapper::EvDef(onChanged);

    some_value.MyValue = 77; // With event
    some_value.MyValue.Value = 27; // Without event

    return 0;
}