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/****************************************************************************
**
** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the Technology Preview License Agreement accompanying
** this package.
**
** GNU Free Documentation License
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of this
** file.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\page qdeclarativebasictypes.html
\title QML Basic Types
QML has a set of primitive types, as listed below, that are used throughout
the \l {QML Elements}.
Some of these types can also be used for defining
\c property values in QML. See \l{Writing QML Components: Properties, Methods and Signals} for the
list of types that can be used for \c property values.
\annotatedlist qmlbasictypes
*/
/*!
\qmlbasictype int
\ingroup qmlbasictypes
\brief An integer is a whole number, e.g. 0, 10, or -20.
An integer is a whole number, e.g. 0, 10, or -20. The possible \c
int values range from around -2000000000 to around 2000000000,
although most elements will only accept a reduced range (which they
mention in their documentation).
Example:
\qml
Item { width: 100; height: 200 }
\endqml
\sa {QML Basic Types}
*/
/*!
\qmlbasictype bool
\ingroup qmlbasictypes
\brief A boolean is a binary true/false value.
A boolean is a binary true/false value.
Example:
\qml
Item { focus: true; clip: false }
\endqml
\sa {QML Basic Types}
*/
/*!
\qmlbasictype real
\ingroup qmlbasictypes
\brief A real number has a decimal point, e.g. 1.2 or -29.8.
A real number has a decimal point, e.g. 1.2 or -29.8.
Example:
\qml
Item { width: 100.45; height: 150.82 }
\endqml
\note In QML all reals are stored in single precision, \l
{http://en.wikipedia.org/wiki/IEEE_754} {IEEE floating point}
format.
\sa {QML Basic Types}
*/
/*!
\qmlbasictype double
\ingroup qmlbasictypes
\brief A double number has a decimal point and is stored in double precision.
A double number has a decimal point and is stored in double precision, \l
{http://en.wikipedia.org/wiki/IEEE_754} {IEEE floating point}
format.
Example:
\qml
Item {
property double number: 32155.2355
}
\endqml
\sa {QML Basic Types}
*/
/*!
\qmlbasictype string
\ingroup qmlbasictypes
\brief A string is a free form text in quotes, e.g. "Hello world!".
A string is a free form text in quotes, e.g. "Hello world!".
Example:
\qml
Text { text: "Hello world!" }
\endqml
Strings have a \c length attribute that holds the number of
characters in the string.
\sa {QML Basic Types}
*/
/*!
\qmlbasictype url
\ingroup qmlbasictypes
\brief A URL is a resource locator, like a file name.
A URL is a resource locator, like a file name. It can be either
absolute, e.g. "http://qt.nokia.com", or relative, e.g.
"pics/logo.png". A relative URL is resolved relative to the URL of
the component where the URL is converted from a JavaScript string
expression to a url property value.
Example:
\qml
Image { source: "pics/logo.png" }
\endqml
\raw HTML
\endraw
\sa {QML Basic Types}
*/
/*!
\qmlbasictype color
\ingroup qmlbasictypes
\brief A color is a standard color name in quotes.
A color is a standard color name in quotes. It is normally specified
as an \l {http://www.w3.org/TR/SVG/types.html#ColorKeywords} {SVG
color name}. These names include colors like "red", "green" and
"lightsteelblue".
If the color you want isn't part of this list, colors can also be
specified in hexidecimal triplets or quads that take the form \c
"#RRGGBB" and \c "#AARRGGBB" respectively. For example, the color
red corresponds to a triplet of \c "#FF0000" and a slightly
transparent blue to a quad of \c "#800000FF".
Example:
\qml
Rectangle { color: "steelblue" }
Rectangle { color: "transparent" }
Rectangle { color: "#FF0000" }
Rectangle { color: "#800000FF" }
Rectangle { color: "#00000000" } // ARGB fully transparent
\endqml
Or with the \l{QML:Qt::rgba()}{Qt.rgba()}, \l{QML:Qt::hsla()}{Qt.hsla()}, \l{QML:Qt::darker()}{Qt.darker()},
\l{QML:Qt::lighter()}{Qt.lighter()} or \l{QML:Qt::tint()}{Qt.tint()} functions:
\qml
Rectangle { color: Qt.rgba(0.5, 0.5, 0, 1) }
\endqml
\sa {QML Basic Types}
*/
/*!
\qmlbasictype point
\ingroup qmlbasictypes
\brief A point type has x and y attributes.
A \c point type has \c x and \c y attributes.
To create a \c point value, specify it as a "x,y" string:
\qml
CustomObject { myPointProperty: "0,20" }
\endqml
Or use the \l{QML:Qt::point()}{Qt.point()} function:
\qml
CustomObject { myPointProperty: Qt.point(0, 20) }
\endqml
\sa {QML Basic Types}
*/
/*!
\qmlbasictype size
\ingroup qmlbasictypes
\brief A size type has width and height attributes
A \c size type has \c width and \c height attributes.
For example, to read the \l {Image::sourceSize} \c size property:
\qml
Column {
Image { id: image; source: "logo.png" }
Text { text: image.sourceSize.width + "," + image.sourceSize.height }
}
\endqml
To create a \c size value, specify it as a "width x height" string:
\qml
LayoutItem { preferredSize: "150x50" }
\endqml
Or use the \l{QML:Qt::size()}{Qt.size()} function:
\qml
LayoutItem { preferredSize: Qt.size(150, 50) }
\endqml
\sa {QML Basic Types}
*/
/*!
\qmlbasictype rect
\ingroup qmlbasictypes
\brief A rect type has x, y, width and height attributes.
A \c rect type has \c x, \c y, \c width and \c height attributes.
For example, to read the \l {Item::childrenRect.x}{Item::childrenRect} \c rect property:
\qml
Rectangle {
width: childrenRect.width
height: childrenRect.height
Rectangle { width: 100; height: 100 }
}
\endqml
To create a \c rect value, specify it as a "x, y, width x height" string:
\qml
CustomObject { myRectProperty: "50,50,100x100" }
\endqml
Or use the \l{QML:Qt::rect()}{Qt.rect()} function:
\qml
CustomObject { myRectProperty: Qt.rect(50, 50, 100, 100) }
\endqml
\sa {QML Basic Types}
*/
/*!
\qmlbasictype date
\ingroup qmlbasictypes
\brief A date is specified as "YYYY-MM-DD".
To create a \c date value, specify it as a "YYYY-MM-DD" string:
Example:
\qml
MyDatePicker { minDate: "2000-01-01"; maxDate: "2020-12-31" }
\endqml
To read a date value returned from a C++ extension class, use
\l{QML:Qt::formatDate()}{Qt.formatDate()} and \l{QML:Qt::formatDateTime()}{Qt.formatDateTime()}.
\sa {QML Basic Types}
*/
/*!
\qmlbasictype time
\ingroup qmlbasictypes
\brief A time is specified as "hh:mm:ss".
A time is specified as "hh:mm:ss".
Example:
\qml
MyTimePicker { time: "14:22:15" }
\endqml
To read a time value returned from a C++ extension class, use
\l{QML:Qt::formatTime()}{Qt.formatTime()} and \l{QML:Qt::formatDateTime()}{Qt.formatDateTime()}.
\sa {QML Basic Types}
*/
/*!
\qmlbasictype font
\ingroup qmlbasictypes
\brief A font type has the properties of a QFont.
A font type has the properties of a QFont. The properties are:
\list
\o \c string font.family
\o \c bool font.bold
\o \c bool font.italic
\o \c bool font.underline
\o \c real font.pointSize
\o \c int font.pixelSize
\endlist
Example:
\qml
Text { font.family: "Helvetica"; font.pointSize: 13; font.bold: true }
\endqml
\sa {QML Basic Types}
*/
/*!
\qmlbasictype action
\ingroup qmlbasictypes
\brief The action type has all the properties of QAction.
The action type has all the properties of QAction. The properties
are:
\list
\o \c slot action.trigger - invoke the action
\o \c bool action.enabled - true if the action is enabled
\o \c string action.text - the text associated with the action
\endlist
Actions are used like this:
\qml
MouseArea { onClicked: myaction.trigger() }
State { name: "enabled"; when: myaction.enabled == true }
Text { text: someaction.text }
\endqml
\sa {QML Basic Types}
*/
/*!
\qmlbasictype list
\ingroup qmlbasictypes
\brief A list of objects.
A list type contains a list of objects. While not technically
a basic type, QML supports lists of object types. When used
from QML, the engine automatically appends each value to the list.
Items in the list can be accessed by index using the usual
\c listName[index] syntax.
For example, the \l Item class contains a list property named
children that can be used like this:
\qml
Item {
children: [
Item { id: child1 },
Rectangle { id: child2; width: 200 },
Text { id: child3 }
]
Component.onCompleted: {
console.log("Width of child rectangle:", children[1].width)
}
}
\endqml
\c child1, \c child2 and \c child3 will be added to the children list
in the order in which they appear.
List \l {Adding Properties}{properties} can be created as a
\c variant type, or as a \c list<Type> type, where \c Type is the
type of the object in the list:
\qml
Item {
property variant values: [ 10, 20, 'abc', 'xyz' ]
property list<Rectangle> rects: [
Rectangle { width: 100; height: 100},
Rectangle { width: 200; height: 200}
]
}
\endqml
A \c variant list can contain values of any of the \l {QML Basic Types}{basic QML types}
such as numbers, strings, etc. while a \c list<Type> list can only contain values
that match (or are derived from) the specified \c Type.
A list property can be cleared by setting it to an empty list:
\qml
Item {
children: []
}
\endqml
A list property cannot be modified in any other way. Items cannot be dynamically added to
or removed from the list through JavaScript operations; any \c push() operations on the
list only modify a \e copy of the list and not the actual list. (These current limitations
are due to restrictions on \l {Property Binding} where lists are involved.)
You can, however, modify a copy of the list and then reassign the property to the modified
value. Other options are to create an array object from within a \c .js JavaScript file,
or implement a custom list element in C++. Here is a QML element that modifies the list in a
JavaScript file:
\table
\row
\o
\qml
// QML
import "script.js" as Script
Item {
Component.onCompleted: {
Script.addItem('abc')
console.log("Added:", Script.getList()[0])
}
}
\endqml
\o
\code
// script.js
var myArray = new Array()
function getList() {
return myArray
}
function addItem(item) {
myArray.push(item)
}
\endcode
\endtable
However, note that a JavaScript list should not be used as a QML \c property value,
as the property is not updated when the list changes.
\sa {QML Basic Types}
*/
/*!
\qmlbasictype variant
\ingroup qmlbasictypes
\brief A variant type is a generic property type.
A variant is a generic property type. A variant type property can hold any of the
\l {QML Basic Types}{basic type} values:
\qml
Item {
property variant aNumber : 100
property variant aString : "Hello world!"
property variant aList : [ 1, 2, "buckle my shoe" ]
}
\endqml
The \c variant type can also hold a \e copy of a JavaScript object. For example, the
\c animal property below defines a JavaScript object defined with JSON notation. The
object's properties and values can be examined using the standard JavaScript syntax,
as shown in the \c Component.onCompleted handler.
\qml
Item {
property variant animal : { 'type': 'bird', 'species': 'galah', 'age': 7 }
Component.onCompleted: {
for (var attribute in animal)
console.log(attribute, "=", animal[attribute])
}
}
\endqml
It must be noted that the \c animal property holds a \e copy of the defined object, and
not the object itself. (This is true even if the property refers to an object defined in
some JavaScript file; the property will hold a copy of the object, and not the actual
object.) The property essentially holds a copy of the contents within the object. This
has several implications:
\list
\o Changes to any of the property's values (for example, the \c animal.type value
above) only modify the \e copy of the object, not the object itself. You can, however,
modify a copy of the object and then reassign the property to the modified value.
\o Because the property only holds a copy of the object, \l{Property Binding}{bindings} to
any of the property's individual values are not updated until the whole property is
reassigned to a new value. For example:
\qml
Item {
property variant animal : { 'type': 'bird', 'species': 'galah', 'age': 7 }
Text { text: "Animal species: " + animal.species }
Component.onCompleted: {
animal.species = 'kookaburra' // this has no effect on the displayed text
var newObj = animal
newObj.species = 'kookaburra'
animal = newObj // this will update the displayed text
}
}
\endqml
\o Since the object values are copied, it does not hold any reference to the original
object, and extra data such as the object's JavaScript prototype chain is lost in the
process.
\endlist
\sa {QML Basic Types}
*/
/*!
\qmlbasictype vector3d
\ingroup qmlbasictypes
\brief A vector3d type has x, y, and z attributes.
A \c vector3d type has \c x, \c y, and \c z attributes.
To create a \c vector3d value, specify it as a "x,y,z" string:
\qml
Rotation { angle: 60; axis: "0,1,0" }
\endqml
or with the \l{QML:Qt::vector3d()}{Qt.vector3d()} function:
\qml
Rotation { angle: 60; axis: Qt.vector3d(0, 1, 0) }
\endqml
or as separate \c x, \c y, and \c z components:
\qml
Rotation { angle: 60; axis.x: 0; axis.y: 1; axis.z: 0 }
\endqml
\sa {QML Basic Types}
*/
/*!
\qmlbasictype enumeration
\ingroup qmlbasictypes
\brief An enumeration type consists of a set of named values.
An enumeration type consists of a set of named values.
An enumeration value may be specifed as either a string:
\qml
Text { horizontalAlignment: "AlignRight" }
\endqml
or as \c {<Element>.<value>}:
\qml
Text { horizontalAlignment: Text.AlignRight }
\endqml
The second form is preferred.
\sa {QML Basic Types}
*/
|