QtQuick.XmlListModel.XmlRole

For specifying a role to an XmlListModel More...

Properties

• isKey : bool
• name : string
• query : string

Detailed Description

See also Qt QML.

Property Documentation

Defines whether this is a key role. Key roles are used to determine whether a set of values should be updated or added to the XML list model when XmlListModel::reload() is called.

See also XmlListModel.

The name for the role. This name is used to access the model data for this role.

For example, the following model has a role named "title", which can be accessed from the view's delegate:

XmlListModel {
id: xmlModel
// ...
XmlRole {
name: "title"
query: "title/string()"
}
}

ListView {
model: xmlModel
delegate: Text { text: title }
}

The relative XPath expression query for this role. The query must be relative; it cannot start with a '/'.

For example, if there is an XML document like this:

<?xml version="1.0" encoding="iso-8859-1" ?>
<catalog>
<book type="Online" wanted="true">
<title>Qt 5 Cadaques</title>
<year>2014</year>
<author>Juergen Bocklage-Ryannel</author>
<author>Johan Thelin</author>
</book>
<book type="Hardcover">
<title>C++ GUI Programming with Qt 4</title>
<year>2006</year>
<author>Jasmin Blanchette</author>
<author>Mark Summerfield</author>
</book>
<book type="Paperback">
<title>Programming with Qt</title>
<year>2002</year>
<author>Matthias Kalle Dalheimer</author>
</book>
</catalog>

Here are some valid XPath expressions for XmlRole queries on this document:

XmlListModel {
id: model
...
// XmlRole queries will be made on <book> elements
query: "/catalog/book"
// query the book title
XmlRole { name: "title"; query: "title/string()" }
// query the book's year
XmlRole { name: "year"; query: "year/number()" }
// query the book's type (the '@' indicates 'type' is an attribute, not an element)
XmlRole { name: "type"; query: "@type/string()" }
// query the book's first listed author (note in XPath the first index is 1, not 0)
XmlRole { name: "first_author"; query: "author[1]/string()" }
// query the wanted attribute as a boolean
XmlRole { name: "wanted"; query: "boolean(@wanted)" }
}

Accessing the model data for the above roles from a delegate:

ListView {
width: 300; height: 200
model: model
delegate: Column {
Text { text: title + " (" + type + ")"; font.bold: wanted }
Text { text: first_author }
Text { text: year }
}

See the href="http://www.w3.org/TR/xpath20/">W3C XPath 2.0 specification for more information.