QUiLoader errơr when loading .ui file - qt

Question

I'm trying to load a simple .ui file using QUiLoader and I'm getting the following error:
Designer: An error has occurred while reading the UI file at line 1, column 0: Premature end of document.
I checked that the .ui file exists and printed its contents.
Code:
QApplication a(argc, argv);
MainWindow w;
w.show();
QUiLoader loader;
qDebug()<< QDir::currentPath();
QFile file("customwidget.ui");
qDebug() <<"File open: "<< file.open(QIODevice::ReadOnly| QIODevice::Text );
QWidget *formWidget;
qDebug() << file.readAll();
qDebug() <<"Loader: "<<(formWidget=loader.load(&file,&w));
file.close();
formWidget->show();
return a.exec();
Output:
"/home"
File open: true
"<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>customWidget</class>
<widget class="QWidget" name="customWidget">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>200</width>
<height>200</height>
</rect>
</property>
<property name="windowTitle">
<string>Form</string>
</property>
<widget class="QPushButton" name="pushButton">
<property name="geometry">
<rect>
<x>50</x>
<y>60</y>
<width>87</width>
<height>27</height>
</rect>
</property>
<property name="text">
<string>PushButton</string>
</property>
</widget>
</widget>
<resources/>
<connections/>
</ui>
"
Designer: An error has occurred while reading the UI file at line 1, column 0: Premature end of document.
Loader: QObject(0x0)
The customwidget.ui file was generated using the QTDesigner and is placed at /home.
Why is this not working?

Answer 1

you already read the entire file, do a file.reset() before the load or just don't read it first:
QUiLoader loader;
qDebug()<< QDir::currentPath();
QFile file("customwidget.ui");
qDebug() <<"File open: "<< file.open(QIODevice::ReadOnly| QIODevice::Text );
QWidget *formWidget;
qDebug() << file.readAll();
file.reset();//or file.seek(0);
qDebug() <<"Loader: "<<(formWidget=loader.load(&file,&w));
file.close();
formWidget->show();