Is it possible to add some behavior at the beginning of Qt-slot or before?

bduminyuk

I use an auth form. Its implementation is not mine, so I cannot change it. The form has two fields for a login and password and also two buttons (ok + cancel).

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:

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

I want it to work:

user clicks ok
verifying if the login match mask and check if the fields are not empty
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?

Christian Ehrlicher

You have to modify AuthForm to achieve what you want. How should it work otherwise? You don't have access to the ui elements outside AuthForm and even then you could not stop on_btn_ok_clicked() from being called without modifying the AuthForm code.

mpergand

You can listen to textChanged signal of lineEdit and enable/disable the button accordingly:

ui->setupUi(this);

   connect(ui->loginLineEdit,&QLineEdit::textChanged,[this](const QString &text)
       {
       QPushButton* okBut=ui->buttonBox->button(QDialogButtonBox::Ok);

       // button OK enabled if the field is not empty
       if(text.isEmpty())
           okBut->setEnabled(false);
       else
           okBut->setEnabled(true);

       });

SGaist

Hi,

Even shorter and just as clear:

connect(ui->loginLineEdit,&QLineEdit::textChanged,[this](const QString &text)
   {
       QPushButton* okBut=ui->buttonBox->button(QDialogButtonBox::Ok);
       okBut->setDisabled(text.isEmpty());
   });