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# QXmlStreamWriter Class Reference
[QtCore module]

The QXmlStreamWriter class provides an XML writer with a simple streaming API. More...

### Methods

- __init__ (self)
- __init__ (self, QIODevice device)
- __init__ (self, QByteArray array)
- __init__ (self, QString string)
- bool autoFormatting (self)
- int autoFormattingIndent (self)
- QTextCodec codec (self)
- QIODevice device (self)
- bool hasError (self)
- setAutoFormatting (self, bool)
- setAutoFormattingIndent (self, int spaces)
- setCodec (self, QTextCodec codec)
- setCodec (self, str codecName)
- setDevice (self, QIODevice device)
- writeAttribute (self, QString qualifiedName, QString value)
- writeAttribute (self, QString namespaceUri, QString name, QString value)
- writeAttribute (self, QXmlStreamAttribute attribute)
- writeAttributes (self, QXmlStreamAttributes attributes)
- writeCDATA (self, QString text)
- writeCharacters (self, QString text)
- writeComment (self, QString text)
- writeCurrentToken (self, QXmlStreamReader reader)
- writeDefaultNamespace (self, QString namespaceUri)
- writeDTD (self, QString dtd)
- writeEmptyElement (self, QString qualifiedName)
- writeEmptyElement (self, QString namespaceUri, QString name)
- writeEndDocument (self)
- writeEndElement (self)
- writeEntityReference (self, QString name)
- writeNamespace (self, QString namespaceUri, QString prefix = '')
- writeProcessingInstruction (self, QString target, QString data = '')
- writeStartDocument (self)
- writeStartDocument (self, QString version)
- writeStartDocument (self, QString version, bool standalone)
- writeStartElement (self, QString qualifiedName)
- writeStartElement (self, QString namespaceUri, QString name)
- writeTextElement (self, QString qualifiedName, QString text)
- writeTextElement (self, QString namespaceUri, QString name, QString text)

## Detailed Description

The QXmlStreamWriter class provides an XML writer with a simple streaming API.

QXmlStreamWriter is the counterpart to QXmlStreamReader for writing XML. Like its related class, it operates on a QIODevice specified with setDevice(). The API is simple and straightforward: for every XML token or event you want to write, the writer provides a specialized function.

You start a document with writeStartDocument() and end it with writeEndDocument(). This will implicitly close all remaining open tags.

Element tags are opened with writeStartElement() followed by writeAttribute() or writeAttributes(), element content, and then writeEndElement(). A shorter form writeEmptyElement() can be used to write empty elements, followed by writeAttributes().

Element content consists of either characters, entity references or nested elements. It is written with writeCharacters(), which also takes care of escaping all forbidden characters and character sequences, writeEntityReference(), or subsequent calls to writeStartElement(). A convenience method writeTextElement() can be used for writing terminal elements that contain nothing but text.

The following abridged code snippet shows the basic use of the class to write formatted XML with indentation:

         QXmlStreamWriter stream(&output);
         stream.setAutoFormatting(true);
         stream.writeStartDocument();
         ...
         stream.writeStartElement("bookmark");
         stream.writeAttribute("href", "http://qt.nokia.com/");
         stream.writeTextElement("title", "Qt Home");
         stream.writeEndElement(); // bookmark
         ...
         stream.writeEndDocument();

QXmlStreamWriter takes care of prefixing namespaces, all you have to do is specify the `namespaceUri` when writing elements or attributes. If you must conform to certain prefixes, you can force the writer to use them by declaring the namespaces manually with either writeNamespace() or writeDefaultNamespace(). Alternatively, you can bypass the stream writer's namespace support and use overloaded methods that take a qualified name instead. The namespace http://www.w3.org/XML/1998/namespace is implicit and mapped to the prefix xml.

The stream writer can automatically format the generated XML data by adding line-breaks and indentation to empty sections between elements, making the XML data more readable for humans and easier to work with for most source code management systems. The feature can be turned on with the autoFormatting property, and customized with the autoFormattingIndent property.

Other functions are writeCDATA(), writeComment(), writeProcessingInstruction(), and writeDTD(). Chaining of XML streams is supported with writeCurrentToken().

By default, QXmlStreamWriter encodes XML in UTF-8. Different encodings can be enforced using setCodec().

If an error occurs while writing to the underlying device, hasError() starts returning true and subsequent writes are ignored.

The QXmlStream Bookmarks Example illustrates how to use a stream writer to write an XML bookmark file (XBEL) that was previously read in by a QXmlStreamReader.

## Method Documentation

### QXmlStreamWriter.__init__ (self)

Constructs a stream writer.

See also setDevice().

### QXmlStreamWriter.__init__ (self, QIODevice device)

Constructs a stream writer that writes into device;

### QXmlStreamWriter.__init__ (self, QByteArray array)

Constructs a stream writer that writes into array. This is the same as creating an xml writer that operates on a QBuffer device which in turn operates on array.

### QXmlStreamWriter.__init__ (self, QString string)

Constructs a stream writer that writes into string.

### bool QXmlStreamWriter.autoFormatting (self)

### int QXmlStreamWriter.autoFormattingIndent (self)

### QTextCodec QXmlStreamWriter.codec (self)

Returns the codec that is currently assigned to the stream.

See also setCodec().

### QIODevice QXmlStreamWriter.device (self)

Returns the current device associated with the QXmlStreamWriter, or 0 if no device has been assigned.

See also setDevice().

### bool QXmlStreamWriter.hasError (self)

Returns true if the stream failed to write to the underlying device; otherwise returns false.

The error status is never reset. Writes happening after the error occurred are ignored, even if the error condition is cleared.

This function was introduced in Qt 4.8.

### QXmlStreamWriter.setAutoFormatting (self, bool)

### QXmlStreamWriter.setAutoFormattingIndent (self, int spaces)

### QXmlStreamWriter.setCodec (self, QTextCodec codec)

Sets the codec for this stream to codec. The codec is used for encoding any data that is written. By default, QXmlStreamWriter uses UTF-8.

The encoding information is stored in the initial xml tag which gets written when you call writeStartDocument(). Call this function before calling writeStartDocument().

See also codec().

### QXmlStreamWriter.setCodec (self, str codecName)

Sets the codec for this stream to the QTextCodec for the encoding specified by codecName. Common values for `codecName` include "ISO 8859-1", "UTF-8", and "UTF-16". If the encoding isn't recognized, nothing happens.

See also QTextCodec.codecForName().

### QXmlStreamWriter.setDevice (self, QIODevice device)

Sets the current device to device. If you want the stream to write into a QByteArray, you can create a QBuffer device.

See also device().

### QXmlStreamWriter.writeAttribute (self, QString qualifiedName, QString value)

Writes an attribute with name and value, prefixed for the specified namespaceUri. If the namespace has not been declared yet, QXmlStreamWriter will generate a namespace declaration for it.

This function can only be called after writeStartElement() before any content is written, or after writeEmptyElement().

### QXmlStreamWriter.writeAttribute (self, QString namespaceUri, QString name, QString value)

This is an overloaded function.

Writes an attribute with qualifiedName and value.

This function can only be called after writeStartElement() before any content is written, or after writeEmptyElement().

### QXmlStreamWriter.writeAttribute (self, QXmlStreamAttribute attribute)

This is an overloaded function.

Writes the attribute.

This function can only be called after writeStartElement() before any content is written, or after writeEmptyElement().

### QXmlStreamWriter.writeAttributes (self, QXmlStreamAttributes attributes)

Writes the attribute vector attributes. If a namespace referenced in an attribute not been declared yet, QXmlStreamWriter will generate a namespace declaration for it.

This function can only be called after writeStartElement() before any content is written, or after writeEmptyElement().

See also writeAttribute() and writeNamespace().

### QXmlStreamWriter.writeCDATA (self, QString text)

Writes text as CDATA section. If text contains the forbidden character sequence "]]>", it is split into different CDATA sections.

This function mainly exists for completeness. Normally you should not need use it, because writeCharacters() automatically escapes all non-content characters.

### QXmlStreamWriter.writeCharacters (self, QString text)

Writes text. The characters "<", "&", and """ are escaped as entity references "&lt;", "&amp;, and "&quot;". To avoid the forbidden sequence "]]>", ">" is also escaped as "&gt;".

See also writeEntityReference().

### QXmlStreamWriter.writeComment (self, QString text)

Writes text as XML comment, where text must not contain the forbidden sequence "--" or end with "-". Note that XML does not provide any way to escape "-" in a comment.

### QXmlStreamWriter.writeCurrentToken (self, QXmlStreamReader reader)

Writes the current state of the reader. All possible valid states are supported.

The purpose of this function is to support chained processing of XML data.

See also QXmlStreamReader.tokenType().

### QXmlStreamWriter.writeDefaultNamespace (self, QString namespaceUri)

Writes a default namespace declaration for namespaceUri.

If writeStartElement() or writeEmptyElement() was called, the declaration applies to the current element; otherwise it applies to the next child element.

Note that the namespaces http://www.w3.org/XML/1998/namespace (bound to xmlns) and http://www.w3.org/2000/xmlns/ (bound to xml) by definition cannot be declared as default.

### QXmlStreamWriter.writeDTD (self, QString dtd)

Writes a DTD section. The dtd represents the entire doctypedecl production from the XML 1.0 specification.

### QXmlStreamWriter.writeEmptyElement (self, QString qualifiedName)

Writes an empty element with name, prefixed for the specified namespaceUri. If the namespace has not been declared, QXmlStreamWriter will generate a namespace declaration for it. Subsequent calls to writeAttribute() will add attributes to this element.

See also writeNamespace().

### QXmlStreamWriter.writeEmptyElement (self, QString namespaceUri, QString name)

This is an overloaded function.

Writes an empty element with qualified name qualifiedName. Subsequent calls to writeAttribute() will add attributes to this element.

### QXmlStreamWriter.writeEndDocument (self)

Closes all remaining open start elements and writes a newline.

See also writeStartDocument().

### QXmlStreamWriter.writeEndElement (self)

Closes the previous start element.

See also writeStartElement().

### QXmlStreamWriter.writeEntityReference (self, QString name)

Writes the entity reference name to the stream, as "&name;".

### QXmlStreamWriter.writeNamespace (self, QString namespaceUri, QString prefix = '')

Writes a namespace declaration for namespaceUri with prefix. If prefix is empty, QXmlStreamWriter assigns a unique prefix consisting of the letter 'n' followed by a number.

If writeStartElement() or writeEmptyElement() was called, the declaration applies to the current element; otherwise it applies to the next child element.

Note that the prefix xml is both predefined and reserved for http://www.w3.org/XML/1998/namespace, which in turn cannot be bound to any other prefix. The prefix xmlns and its URI http://www.w3.org/2000/xmlns/ are used for the namespace mechanism itself and thus completely forbidden in declarations.

### QXmlStreamWriter.writeProcessingInstruction (self, QString target, QString data = '')

Writes an XML processing instruction with target and data, where data must not contain the sequence "?>".

### QXmlStreamWriter.writeStartDocument (self)

Writes a document start with the XML version number version.

See also writeEndDocument().

### QXmlStreamWriter.writeStartDocument (self, QString version)

Writes a document start with the XML version number version and a standalone attribute standalone.

This function was introduced in Qt 4.5.

See also writeEndDocument().

### QXmlStreamWriter.writeStartDocument (self, QString version, bool standalone)

This is an overloaded function.

Writes a document start with XML version number "1.0". This also writes the encoding information.

This function was introduced in Qt 4.5.

See also writeEndDocument() and setCodec().

### QXmlStreamWriter.writeStartElement (self, QString qualifiedName)

Writes a start element with name, prefixed for the specified namespaceUri. If the namespace has not been declared yet, QXmlStreamWriter will generate a namespace declaration for it. Subsequent calls to writeAttribute() will add attributes to this element.

See also writeNamespace(), writeEndElement(), and writeEmptyElement().

### QXmlStreamWriter.writeStartElement (self, QString namespaceUri, QString name)

This is an overloaded function.

Writes a start element with qualifiedName. Subsequent calls to writeAttribute() will add attributes to this element.

See also writeEndElement() and writeEmptyElement().

### QXmlStreamWriter.writeTextElement (self, QString qualifiedName, QString text)

Writes a text element with name, prefixed for the specified namespaceUri, and text. If the namespace has not been declared, QXmlStreamWriter will generate a namespace declaration for it.

This is a convenience function equivalent to:

             writeStartElement(namespaceUri, name);
             writeCharacters(text);
             writeEndElement();

### QXmlStreamWriter.writeTextElement (self, QString namespaceUri, QString name, QString text)

This is an overloaded function.

Writes a text element with qualifiedName and text.

This is a convenience function equivalent to:

             writeStartElement(qualifiedName);
             writeCharacters(text);
             writeEndElement();