QObject connection function

Question

I checked other similar questions and tried their solutions but they don't work for me.

I'm basically trying to make a http client that only makes post requests. In order to do this, I need to connect QNetworkManager's finished signal to some callback slot.

Here's my code.

h file:

... public slots:    void finishedSlot(QNetworkReply* reply); private:     QNetworkAccessManager *network_manager; ... 

cpp file:

... Class1::Class1(){     network_manager = new QNetworkAccessManager(this);     QObject::connect(network_manager, SIGNAL(finished(QNetworkReply *)), this, SLOT(finishedSlot(QNetworkReply *))); } ... void Class1::finishedSlot(QNetworkReply* reply) {     // some logic with reply } ... 

As you can see, the slot is definitely present and it is declared under public slots in header file. So I have no idea why this is happening. I already tried clean, run qmake, and rebuild.

The error message is:

"QObject::connect: No such slot QObject::finishedSlot(QNetworkReply *)"

Any idea?

Answer 1

You probably forgot to use the Q_OBJECT macro. Every class that implements its own slots/signals needs that macro. Don't forget that you need to add your header/source file to the .pro file.

Answer 2

One thing to note; since you're using Qt 5, there's a new signal slot connection syntax, which will allow you to specify any function and not just those defined as slots.

In this situation you can do this: -

connect(network_manager, &QNetworkAccessManager::finished, this, &Class1::finishedSlot); 

What's great about this syntax is that you just specify the address of the function and don't bother about the parameters, so if you change them in a function, you don't need to update them in the connect statements.

You still should be using the Q_OBJECT macro though and you can read more about the new syntax here.