Passing user Input to Slots

[JohnSRV]

Hey Everyone,

I'm new to Qt and I find the Signal/Slot Concept in this Framework really helpful. I'm doing some GUI Programming and I'm trying to get some user Input and then do some actions with it. So I have some Qpush Buttons in my GUI when the User clicks one of them he is asked to insert a number or a String.

How can I pass the Input to a Slot that works with it ?

[JonB]

@JohnSRV
The slot for clicking the pushbutton does not itself do anything with/know about the number/string you are about to "ask for"; it hasn't happened yet! I trust you get that bit.

When the user has clicked the button, how do you intend to "[ask user] to insert a number or a String"? How are you going to prompt for that? Only after that can we discuss how you might use signals/slots to forward the data input onto something else.

[mrjj]

Hi
How do you then get this number or string?

[JohnSRV]

@JonB after the User clicks the Button a Dialog Window pops up where the User can insert an IP Adress for example.

void boxconec::Target_IP()
{
	QString TargetIP = QInputDialog::getText(this, "Choose Target system", "Enter the IP Address of the Target System:");
	ui->IPAdress->setText(TargetIP);
}

So I want to pass this TargetIP Variable to a Function that connects to a QTcp Server listening under the given Address. How can I pass that information to my Client Function?

[mrjj]

@JohnSRV
How does you client function look like ?
can you just add the new parameter and call it

void boxconec::Target_IP()
{
	QString TargetIP = QInputDialog::getText(this, "Choose Target system", "Enter the IP Address of the Target System:");
	ui->IPAdress->setText(TargetIP);
ClientFunction(TargetIP);
}

[JonB]

@JohnSRV
I will leave you in my colleague @mrjj's capable hands for guiding you now :)

[JohnSRV]

@mrjj Hey thanks for your reply and sorry for my late Reply. My Client Function is not complete so I tried to test this with a Simple QFile.

void BoxConnector::ProjectButtonPushed()
{
	QString ProjectPath_UserInput = QInputDialog::getText(this, "Project", "Enter the Path to the Project");
	ui->Project_Path->setText(ProjectPath_UserInput);
	QFile Project (Project_UserInput ); 
	if (Project.exists())
	{
		QMessageBox msgBox; 
		msgBox.setText("Opening the Project..");
	}
	else
	{
		QMessageBox ErrorBox; 
		ErrorBox.setText("couldn't find the Project..");
	}
}

I can't seem to get a Message box neither for "Opening the Project.." nor for "couldn't find with the Project". Does the User Input get passed correctly to the QFile with this Code??

[mrjj]

Hi
You need to call msgBox.exec(); to have it show.
Currently, you just set its text but dont tell it to show:=)
https://doc.qt.io/qt-5/qmessagebox.html

Also since you want the user to input the FULL path to a project what about using FileDialog instead so the user can browse to file and not have to type it all?

https://doc.qt.io/qt-5/qfiledialog.html

[JonB]

@JohnSRV
QMessageBox::setText() simply sets the text for the message box, it does not show it. You need to call QMessageBox::exec() to do that.

[JohnSRV]

Thank you all for your help ! I solved my problem with the snippet from @mrjj

void boxconec::Target_IP()
{
	QString TargetIP = QInputDialog::getText(this, "Choose Target system", "Enter the IP Address of the Target System:");
	ui->IPAdress->setText(TargetIP);
ClientFunction(TargetIP);
}

The Application will get more complicated where the ClientFunction returns a Value that has to be passed to another slot but I'm not there yet. As for now I'm gonna mark this question as solved.

Thank you !

[JonB]

@JohnSRV
What you have ended up with is fine. But be aware you have not encountered any signal/slot stuff in it. In effect, the signal/slot stuff is being hidden from you inside QInputDialog::getText(), and what you see at this level is a synchronous program.

[JohnSRV]

Hello Everyone,

I'm back on this topic now. I have a GUI where the User can choose which Project he wants to work with. When he pushes the Button "choose Project" a QFileDialog gets opened.

void BoxConnector::ProjectButtonPushed()
{
QString ProjectPath_UserInput = QFileDialog::getOpenFileName(this, tr("Open Project"), "C:/Users/Project");

Now I have many other buttons in my GUI where the user could manipulate the chosen project. How Can I pass the Path of the chosen Project to the other Slots?

I for example have a Button where the User could insert a Simulation Step Size

void BoxConnector::SimStepSizePushed()
{
	QString SimSize_UserInput = QInputDialog::getText(this, "Simulation Step Size", "Insert Simulation Step Size");
}

How Can I pass the Path of the chosen Project in the first Slot to this Slot for example so I could manipulate the Simulation Step Size of the chosen Project?

[mrjj]

Hi
Just make
QString ProjectPath_UserInput;
a member of BoxConnector
so all slots and methods has access.

[JohnSRV]

@mrjj I declared a QString in the BoxConnector.h.

Its Value gets set in the ProjectButtonPushed() Slot. When I call this String in another Slot it seems to be empty.

[mrjj]

@JohnSRV
make sure you didnt do the classic error.
you line should be be
ProjectPath_UserInput = QFileDialog::getOpenFileName(this, tr("Open Project"), "C:/Users/Project");

and NOT
QString ProjectPath_UserInput = QFileDialog::getOpenFileName(this, tr("Open Project"), "C:/Users/Project");
as then you still use local variable..

[JohnSRV]

As a matter of fact I did make the classic Mistake. Thanks !!!

[mrjj]

@JohnSRV
Thats is why its a classic, very easy to do :)