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| /*! |
| \example schema |
| \title XML Schema Validation Example |
| \ingroup xmlpattern_examples |
| \brief Using Qt XML Patterns to validate XML with a W3C XML Schema. |
| |
| The XML Schema Validation example shows how to use Qt XML Patterns to |
| validate XML with a W3C XML Schema. |
| |
| \tableofcontents |
| |
| \section1 Introduction |
| |
| The example application shows different XML schema definitions and |
| for every definition two XML instance documents, one that is valid |
| according to the schema and one that is not. |
| The user can select the valid or invalid instance document, change |
| it and validate it again. |
| |
| \section2 The User Interface |
| |
| The UI for this example was created using \l{Qt Designer Manual} {Qt |
| Designer}: |
| |
| \image schema-example.png |
| |
| The UI consists of three parts, at the top the XML schema \l{QComboBox} {selection} |
| and the schema \l{QTextBrowser} {viewer}, below the XML instance \l{QComboBox} {selection} |
| and the instance \l{QTextEdit} {editor} and at the bottom the validation status \l{QLabel} {label} |
| next to the validation \l{QPushButton} {button}. |
| |
| \section2 Validating XML Instance Documents |
| |
| You can select one of the three predefined XML schemas and for each schema |
| an valid or invalid instance document. A click on the 'Validate' button will |
| validate the content of the XML instance editor against the schema from the |
| XML schema viewer. As you can modify the content of the instance editor, different |
| instances can be tested and validation error messages analysed. |
| |
| \section1 Code Walk-Through |
| |
| The example's main() function creates the standard instance of |
| QApplication. Then it creates an instance of the mainwindow class, shows it, |
| and starts the Qt event loop: |
| |
| \snippet schema/main.cpp 0 |
| |
| \section2 The UI Class: MainWindow |
| |
| The example's UI is a conventional Qt GUI application inheriting |
| QMainWindow and the class generated by \l{Qt Designer Manual} {Qt |
| Designer}: |
| |
| \snippet schema/mainwindow.h 0 |
| |
| The constructor fills the schema and instance \l{QComboBox} selections with the predefined |
| schemas and instances and connects their \l{QComboBox::currentIndexChanged()} {currentIndexChanged()} |
| signals to the window's \c{schemaSelected()} resp. \c{instanceSelected()} slot. |
| Furthermore the signal-slot connections for the validation \l{QPushButton} {button} |
| and the instance \l{QTextEdit} {editor} are set up. |
| |
| The call to \c{schemaSelected(0)} and \c{instanceSelected(0)} will trigger the validation |
| of the initial Contact Schema example. |
| |
| \snippet schema/mainwindow.cpp 0 |
| |
| In the \c{schemaSelected()} slot the content of the instance \l{QComboBox} {selection} |
| is adapted to the selected schema and the corresponding schema is loaded from the |
| \l{The Qt Resource System} {resource file} and displayed in the schema \l{QTextBrowser} {viewer}. |
| At the end of the method a revalidation is triggered. |
| |
| \snippet schema/mainwindow.cpp 1 |
| |
| In the \c{instanceSelected()} slot the selected instance is loaded from the |
| \l{The Qt Resource System} {resource file} and loaded into the instance \l{QTextEdit} {editor} |
| an the revalidation is triggered again. |
| |
| \snippet schema/mainwindow.cpp 2 |
| |
| The \c{validate()} slot does the actual work in this example. |
| At first it stores the content of the schema \l{QTextBrowser} {viewer} and the |
| \l{QTextEdit} {editor} into temporary \l{QByteArray} {variables}. |
| Then it instanciates a \c{MessageHandler} object which inherits from |
| \l{QAbstractMessageHandler} {QAbstractMessageHandler} and is a convenience |
| class to store error messages from the XmlPatterns system. |
| |
| \snippet schema/mainwindow.cpp 4 |
| |
| After the \l{QXmlSchema} {QXmlSchema} is instanciated and the message handler set |
| on it, the \l{QXmlSchema::load()} {load()} method is called with the schema data as argument. |
| If the schema is invalid or a parsing error has occurred, \l{QXmlSchema::isValid()} {isValid()} |
| returns \c{false} and the error is flagged in \c{errorOccurred}. |
| If the loading was successful, a \l{QXmlSchemaValidator} {QXmlSchemaValidator} is |
| instanciated and the schema passed in the constructor. |
| A call to \l{QXmlSchemaValidator::validate()} {validate()} will validate the passed |
| XML instance data against the XML schema. The return value of that method signals |
| whether the validation was successful. |
| Depending on the success the status \l{QLabel} {label} is set to 'validation successful' |
| or the error message stored in the \c{MessageHandler} |
| |
| The rest of the code does only some fancy coloring and eyecandy. |
| |
| \snippet schema/mainwindow.cpp 3 |
| */ |