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# QXmlSchema Class Reference
[QtXmlPatterns module]

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

### Methods

- __init__ (self)
- QUrl documentUri (self)
- bool isValid (self)
- bool load (self, QUrl)
- bool load (self, QIODevice, QUrl documentUri = QUrl())
- bool load (self, QByteArray, QUrl documentUri = QUrl())
- QAbstractMessageHandler messageHandler (self)
- QXmlNamePool namePool (self)
- QNetworkAccessManager networkAccessManager (self)
- setMessageHandler (self, QAbstractMessageHandler)
- setNetworkAccessManager (self, QNetworkAccessManager)
- setUriResolver (self, QAbstractUriResolver)
- QAbstractUriResolver uriResolver (self)

## Detailed Description

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

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";

See also QXmlSchemaValidator and XML Schema Validation Example.

## Method Documentation

### QXmlSchema.__init__ (self)

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

### QUrl QXmlSchema.documentUri (self)

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

### bool QXmlSchema.isValid (self)

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 (self, QUrl)

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 (self, QIODevice, 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 (self, QByteArray, 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://qt.nokia.com/xmlschematest\""
                          "        targetNamespace=\"http://qt.nokia.com/xmlschematest\""
                          "        version=\"1.0\""
                          "        elementFormDefault=\"qualified\">"
                          "</xsd:schema>" );

         QBuffer buffer(&data);
         buffer.open(QIODevice.ReadOnly);

         QXmlSchema schema;
         schema.load(&buffer);

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

See also isValid() and isValid().

### QAbstractMessageHandler QXmlSchema.messageHandler (self)

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

See also setMessageHandler().

### QXmlNamePool QXmlSchema.namePool (self)

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 (self)

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

See also setNetworkAccessManager().

### QXmlSchema.setMessageHandler (self, QAbstractMessageHandler)

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().

### QXmlSchema.setNetworkAccessManager (self, QNetworkAccessManager)

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

See also networkAccessManager().

### QXmlSchema.setUriResolver (self, QAbstractUriResolver)

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

See also uriResolver().

### QAbstractUriResolver QXmlSchema.uriResolver (self)

Returns the schema's URI resolver. If no URI resolver has been set, QtXmlPatterns 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 QtXmlPatterns 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().