[SOLVED] Qt C++, connect class instance signal to Widget main class

Issue

My code contains a function which takes a lot of time to compute. To make it feel more responsive, I wanted to visualize every tenth of the progress with a progress bar. However, the function is implemented in another class other than my Main Widget class and I cannot access the ui elements of the Widget class. I tried putting a signal which can be emitted during the function, however it comes up as an error.
The relevant code looks like this:

//Class cpp implementation
void Dataset::calculateNew(){

for(int i = 0; i<1000; i++){
     if(i%100==0)
       emit valueChanged(i);  //first Error
        for(int j = 0; j<1000; j++){
            for(int k=0; k<1000; k++){

             //Expensive Matrix calculation
        }
     }
  }
} 

//Class .h implementation

signal:
valueChanged(int value);

//Widget implementation
 
connect(Dataset::calculateNew(), SIGNAL(valueChanged(int)), this, SLOT(updateProgressBar(int))); //second Error here
 

Am I thinking in the right way? What should I do to make it work? Or is there another way to access and change ui Elements of the Widget class.

Note:
I tried including the "widget.h" in Dataset class, but it isn´t recognized as a class to be included,

Solution

Hard to say without the minimal example, but I guess the problem lies in your call to connect:

connect(Dataset::calculateNew(), SIGNAL(valueChanged(int)), this, SLOT(updateProgressBar(int))); //second Error here

Provided your dataset object is called ds, it should look like this:
connect(&ds, SIGNAL(valueChanged(int)), this, SLOT(updateProgressBar(int)));

BTW, why don’t you use the new signal-slot syntax based on fucntion pointers? Are you still on QT4?

Answered By – alagner

Answer Checked By – David Goodson (BugsFixing Volunteer)