QXmlSchema Class | Qt XML Patterns 5.15.1

- Qt 5.15
- Qt XML Patterns
- C++ Classes
- QXmlSchema
- Qt 5.15.1 Reference Documentation

# QXmlSchema Class

The QXmlSchema class provides loading and validation of a W3C XML Schema. More...

Header: | #include <QXmlSchema>
qmake: | QT += xmlpatterns
Since: | Qt 4.6

This class was introduced in Qt 4.6.

- List of all members, including inherited members

Note: All functions in this class are reentrant.

## Public Functions

| QXmlSchema(const QXmlSchema &other)
| QXmlSchema()
QXmlSchema & | operator=(const QXmlSchema &other)
| ~QXmlSchema()
QUrl | documentUri() const
bool | isValid() const
bool | load(const QUrl &source)
bool | load(QIODevice *source, const QUrl &documentUri = QUrl())
bool | load(const QByteArray &data, const QUrl &documentUri = QUrl())
QAbstractMessageHandler * | messageHandler() const
QXmlNamePool | namePool() const
QNetworkAccessManager * | networkAccessManager() const
void | setMessageHandler(QAbstractMessageHandler *handler)
void | setNetworkAccessManager(QNetworkAccessManager *manager)
void | setUriResolver(const QAbstractUriResolver *resolver)
const QAbstractUriResolver * | uriResolver() const

## Detailed Description

The QXmlSchema class loads, compiles and validates W3C XML Schema files that can be used further for validation of XML instance documents via QXmlSchemaValidator.

The following example shows how to load a XML Schema file from the network and test whether it is a valid schema document:

         QUrl url("http://www.schema-example.org/myschema.xsd");

         QXmlSchema schema;
         if (schema.load(url) == true)
             qDebug() << "schema is valid";
         else
             qDebug() << "schema is invalid";

### XML Schema Version

This class is used to represent schemas that conform to the XML Schema 1.0 specification.

See also QXmlSchemaValidator and XML Schema Validation Example.

## Member Function Documentation

### QXmlSchema::QXmlSchema(const QXmlSchema &other)

Constructs a QXmlSchema that is a copy of other. The new instance will share resources with the existing schema to the extent possible.

### QXmlSchema::QXmlSchema()

Constructs an invalid, empty schema that cannot be used until load() is called.

### QXmlSchema &QXmlSchema::operator=(const QXmlSchema &other)

Copies the resources of other into this instance, sharing them to the extent possible.

This function was introduced in Qt 5.4.

### QXmlSchema::~QXmlSchema()

Destroys this QXmlSchema.

### QUrl QXmlSchema::documentUri() const

Returns the document URI of the schema or an empty URI if no schema has been set.

### bool QXmlSchema::isValid() const

Returns true if this schema is valid. Examples of invalid schemas are ones that contain syntax errors or that do not conform the W3C XML Schema specification.

### bool QXmlSchema::load(const QUrl &source)

Sets this QXmlSchema to a schema loaded from the source URI.

If the schema is invalid, `false` is returned and the behavior is undefined.

Example:

         QUrl url("http://www.schema-example.org/myschema.xsd");

         QXmlSchema schema;
         if (schema.load(url) == true)
             qDebug() << "schema is valid";
         else
             qDebug() << "schema is invalid";

See also isValid().

### bool QXmlSchema::load(QIODevice *source, const QUrl &documentUri = QUrl())

Sets this QXmlSchema to a schema read from the source device. The device must have been opened with at least QIODevice::ReadOnly.

documentUri represents the schema obtained from the source device. It is the base URI of the schema, that is used internally to resolve relative URIs that appear in the schema, and for message reporting.

If source is `null` or not readable, or if documentUri is not a valid URI, behavior is undefined.

If the schema is invalid, `false` is returned and the behavior is undefined.

Example:

         QFile file("myschema.xsd");
         file.open(QIODevice::ReadOnly);

         QXmlSchema schema;
         schema.load(&file, QUrl::fromLocalFile(file.fileName()));

         if (schema.isValid())
             qDebug() << "schema is valid";
         else
             qDebug() << "schema is invalid";

See also isValid().

### bool QXmlSchema::load(const QByteArray &data, const QUrl &documentUri = QUrl())

Sets this QXmlSchema to a schema read from the data

documentUri represents the schema obtained from the data. It is the base URI of the schema, that is used internally to resolve relative URIs that appear in the schema, and for message reporting.

If documentUri is not a valid URI, behavior is undefined.

If the schema is invalid, `false` is returned and the behavior is undefined.

Example:

         QByteArray data( "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"
                          "<xsd:schema"
                          "        xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\""
                          "        xmlns=\"http://www.qt-project.org/xmlschematest\""
                          "        targetNamespace=\"http://www.qt-project.org/xmlschematest\""
                          "        version=\"1.0\""
                          "        elementFormDefault=\"qualified\">"
                          "</xsd:schema>" );

         QXmlSchema schema;
         schema.load(data);

         if (schema.isValid())
             qDebug() << "schema is valid";
         else
             qDebug() << "schema is invalid";

See also isValid() and isValid().

### QAbstractMessageHandler *QXmlSchema::messageHandler() const

Returns the message handler that handles compile and validation messages for this QXmlSchema.

See also setMessageHandler().

### QXmlNamePool QXmlSchema::namePool() const

Returns the name pool used by this QXmlSchema for constructing names. There is no setter for the name pool, because mixing name pools causes errors due to name confusion.

### QNetworkAccessManager *QXmlSchema::networkAccessManager() const

Returns the network manager, or 0 if it has not been set.

See also setNetworkAccessManager().

### void QXmlSchema::setMessageHandler(QAbstractMessageHandler *handler)

Changes the message handler for this QXmlSchema to handler. The schema sends all compile and validation messages to this message handler. QXmlSchema does not take ownership of handler.

Normally, the default message handler is sufficient. It writes compile and validation messages to stderr. The default message handler includes color codes if stderr can render colors.

When QXmlSchema calls QAbstractMessageHandler::message(), the arguments are as follows:

message() argument | Semantics
--- | ---
QtMsgType type | Only QtWarningMsg and QtFatalMsg are used. The former identifies a warning, while the latter identifies an error.
const QString & description | An XHTML document which is the actual message. It is translated into the current language.
const QUrl &identifier | Identifies the error with a URI, where the fragment is the error code, and the rest of the URI is the error namespace.
const QSourceLocation & sourceLocation | Identifies where the error occurred.

See also messageHandler().

### void QXmlSchema::setNetworkAccessManager(QNetworkAccessManager *manager)

Sets the network manager to manager. QXmlSchema does not take ownership of manager.

See also networkAccessManager().

### void QXmlSchema::setUriResolver(const QAbstractUriResolver *resolver)

Sets the URI resolver to resolver. QXmlSchema does not take ownership of resolver.

See also uriResolver().

### const QAbstractUriResolver *QXmlSchema::uriResolver() const

Returns the schema's URI resolver. If no URI resolver has been set, Qt XML Patterns will use the URIs in schemas as they are.

The URI resolver provides a level of abstraction, or polymorphic URIs. A resolver can rewrite logical URIs to physical ones, or it can translate obsolete or invalid URIs to valid ones.

When Qt XML Patterns calls QAbstractUriResolver::resolve() the absolute URI is the URI mandated by the schema specification, and the relative URI is the URI specified by the user.

See also setUriResolver().