Cannot Call Member Function Without Object

cannot call member function without object

You need to instantiate an object in order to call its member functions. The member functions need an object to operate on; they can't just be used on their own. The main() function could, for example, look like this:

int main()
{
   Name_pairs np;
   cout << "Enter names and ages. Use 0 to cancel.\n";
   while(np.test())
   {
      np.read_names();
      np.read_ages();
   }
   np.print();
   keep_window_open();
}

Cannot call member function without object but I call the function with an object

DisplayAge in Utility is not a static function. Therefore you need an instance of Uitility in order to call it.

So, either make the function static, or call it via an anonymous temporary

Utility().DisplayAge(FirstMan);

Better still, make DisplayAge a member function of Human.

namespace: cannot call member function without object

void pushEvent(Event *event);

This is a non-static function, it cannot be called without an object.
Somewhere you should have an instance of EventManager and use the instance to call pushEvent()

If you want to be able to call this function without object, you need to mark this function as static.

static void pushEvent(Event *event);

error: cannot call member function without object - but I have an object?

If the function validate is not a static member function then you need to specify an object for which it is called as for example

if (game->validate(game->currentCommand())) {

Cannot call member function without object = C++

If you've written the CP_StringToPString function, you need to declare it static:

static void IC_Utility::CP_StringToPString( FxString& inString, FxUChar *outString)

Alternatively, if it's a function in third-party code, you need to declare an IC_Utility object to call it on:

IC_Utility u;
u.CP_StringToPString(text, &outDescription1[0] );

Qt C++ cannot call member function ' ' without object

The error description is pretty clear

cannot call member function 'QString Load::loadRoundsPlayed()'without object

You cannot call member functions, that are not static, without creating instance of the class.

Looking at you code, you probably need to do this:

Load load;
ui->roundPlayer_lcdNumber->display(load.loadRoundsPlayed()); //right here

There are two other options:

make loadRoundsPlayed static and roundsPlayed static, if you don't want them to be associated with the concrete instances OR
make loadRoundsPlayed static and return QString by copy, that will be locally created inside the function. Something like

QString Load::loadRoundsPlayed()
{
    QFile roundsFile(":/StartupFiles/average_rounds.dat");

    if(!roundsFile.open(QFile::ReadOnly | QFile::Text))
    {
        qDebug("Could not open average_rounds for reading");
    }

    QString lRoundsPlayed = roundsFile.readAll();
    roundsFile.close();
    return lRoundsPlayed;
}