- Qt 5.15
- Qt Designer Manual
- C++ Classes
- QAbstractFormBuilder
- Qt 5.15.18 Reference Documentation

# QAbstractFormBuilder Class

The QAbstractFormBuilder class provides a default implementation for classes that create user interfaces at run-time. More...

Header: | #include <QAbstractFormBuilder>
qmake: | QT += designer
Inherited By: | QFormBuilder

- List of all members, including inherited members

## Public Functions

| QAbstractFormBuilder()
virtual | ~QAbstractFormBuilder()
QString | errorString() const
virtual QWidget * | load(QIODevice *device, QWidget *parent = nullptr)
virtual void | save(QIODevice *device, QWidget *widget)
void | setWorkingDirectory(const QDir &directory)
QDir | workingDirectory() const

## Protected Types

(alias) | DomPropertyHash
(alias) | IconPaths

## Detailed Description

QAbstractFormBuilder provides a standard interface and a default implementation for constructing forms from user interface files. It is not intended to be instantiated directly. Use the QFormBuilder class to create user interfaces from UI files at run-time. For example:

             MyForm::MyForm(QWidget *parent)
                 : QWidget(parent)
             {
                 QFormBuilder builder;
                 QFile file(":/forms/myWidget.ui");
                 file.open(QFile::ReadOnly);
                 QWidget *myWidget = builder.load(&file, this);
                 file.close();

                 QVBoxLayout *layout = new QVBoxLayout;
                 layout->addWidget(myWidget);
                 setLayout(layout);
             }

To override certain aspects of the form builder's behavior, subclass QAbstractFormBuilder and reimplement the relevant virtual functions:

- load() handles reading of UI format files from arbitrary QIODevices, and construction of widgets from the XML data that they contain.
- save() handles saving of widget details in UI format to arbitrary QIODevices.
- workingDirectory() and setWorkingDirectory() control the directory in which forms are held. The form builder looks for other resources on paths relative to this directory.

The QFormBuilder class is typically used by custom components and applications that embed Qt Designer. Standalone applications that need to dynamically generate user interfaces at run-time use the QUiLoader, found in the Qt UI Tools module.

See also Qt UI Tools.

## Member Function Documentation

### QAbstractFormBuilder::QAbstractFormBuilder()

Constructs a new form builder.

### `[virtual]` QAbstractFormBuilder::~QAbstractFormBuilder()

Destroys the form builder.

### QString QAbstractFormBuilder::errorString() const

Returns a human-readable description of the last error occurred in load().

This function was introduced in Qt 5.0.

See also load().

### `[virtual]` QWidget *QAbstractFormBuilder::load(QIODevice *device, QWidget *parent = nullptr)

Loads an XML representation of a widget from the given device, and constructs a new widget with the specified parent.

See also save() and errorString().

### `[virtual]` void QAbstractFormBuilder::save(QIODevice *device, QWidget *widget)

Saves an XML representation of the given widget to the specified device in the standard UI file format.

Note: Unlike when saving a form in Qt Designer, all property values are written. This is because, the state of whether a property value was modified or not isn't stored in the Qt property system. The widget that is being saved, could have been created dynamically, not loaded via load(), so in this case the form builder isn't aware of the list of changed properties. Also, there's no generic way to do this for widgets that were created dynamically.

Therefore, you should remove properties that are not required from your resulting XML files, before loading them. Alternatively, if you already know which properties you want to save when you call this method, you can overload `computeProperties()` and return a filtered list of required properties. Otherwise, unexpected behavior may occur as some of these properties may depend on each other.

See also load().

### void QAbstractFormBuilder::setWorkingDirectory(const QDir &directory)

Sets the current working directory of the form builder to the specified directory.

See also workingDirectory().

### QDir QAbstractFormBuilder::workingDirectory() const

Returns the current working directory of the form builder.

See also setWorkingDirectory().