QtE56: QFormBuilder: Error: undefined identifier `QFormBuilder`

[Marcone via Digitalmars-d-learn]

I'm trying to load a .ui GUI designed in Qt Designer. I'm 
following the examples in the links below, but the following 
error occurs: Error: undefined identifier `QFormBuilder`

QFormBuilder qfb = new QFormBuilder(this);
setQtObj((qfb.load(":/fQtE56help.ui")).QtObj);


* https://github.com/MGWL/QtE5/

* https://github.com/MGWL/QtE5/wiki

* https://github.com/MGWL/QtE5/wiki

* https://www.youtube.com/watch?v=TFN5P4eoS_o

Could anyone help me to solve the problem? I would like to design 
my GUI in Qt Designer, and load the .ui to create my program.