Let's imagine the authorize method looks like this (I replaced the code sending requests to a server with one condition inside the if statement):

void AuthForm::on_btn_ok_clicked()
{
    if (loginLineEdit->text() == "auth" && passwordLineEdit->text() == "auth")
        emit accepted();
    else
        emit rejected();
}

I can connect to signals AuthForm::accepted or AuthForm::rejected to get result of authorization. But the problem is the default implementation of AuthForm does not validate form fields. Before the program send requests to authorize the user I want it to check if the form fields are empty or if the login match a mask.

It works:

1. user clicks ok
2. calling of on_btn_ok_clicked() immediately
3. sending requests to get user logged in or not

I want it to work:

1. user clicks ok
2. verifying if the login match mask and check if the fields are not empty
3. using of default on_btn_ok_clicked() implementation

I think it should be like a middle layer between signal and slot. But I don't know if it is possible and how to do it.

So, is it possible to add some behavior at the beginning of Qt-slot not modifying it?