Hello, I am having trouble passing a value from one function in Qt to another in a different form

Beastiary.cpp
Qt Code: 
  1. void beastiary::on_listWidget_itemClicked(QListWidgetItem *item)
  2. {   
  3.    const QString nvalue = ui->listWidget->currentItem()->text(); //Value that needs to passed
  4.    read red;
  5.    red.setModal(true);
  6.    red.exec();
  7.    red.ulk();
  8.  
  9. }
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read.cpp
Qt Code: 
  1. void read::ulk()
  2. {
  3.  
  4.     QFile file (nvalue); //needs nvalue from beastiary so it knows the name of the file to look for
  5.     if (!file.open(QFile::ReadOnly | QFile::Text))
  6.      {
  7.          QMessageBox::warning (this, "Error", "File Could not Be Opened");
  8.  
  9.      }
  10.   QString line;
  11.   QTextStream in(&file);
  12.   while (!in.atEnd())
  13.    {
  14.     line = in.readLine();
  15.     ui->lineEdit_name_r->setText(ui->lineEdit_name_r->text()+line);
  16.     qDebug() <<line;
  17.    }
  18. }
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The variable nvalue must be obtained in beastiary.cpp but is needed in read.cpp and im not sure of how to pass the variable to read from beastiary.