}
\endqml
+ \section1 Change Notification Semantics
+
It is important to note that changes in regular properties of JavaScript
objects assigned to a var property will \b{not} trigger updates of bindings
that access them. The example below will display "The car has 4 wheels" as
car property itself would be changed, which causes a change notification
to be emitted.
+ \section1 Property Value Initialization Semantics
+
+ The QML syntax defines that curly braces on the right-hand-side of a
+ property value initialization assignment denote a binding assignment.
+ This can be confusing when initializing a \c var property, as empty curly
+ braces in JavaScript can denote either an expression block or an empty
+ object declaration. If you wish to initialize a \c var property to an
+ empty object value, you should wrap the curly braces in parentheses.
+
+ For example:
+ \qml
+ Item {
+ property var first: {} // nothing = undefined
+ property var second: {{}} // empty expression block = undefined
+ property var third: ({}) // empty object
+ }
+ \endqml
+
+ In the previous example, the \c first property is bound to an empty
+ expression, whose result is undefined. The \c second property is bound to
+ an expression which contains a single, empty expression block ("{}"), which
+ similarly has an undefined result. The \c third property is bound to an
+ expression which is evaluated as an empty object declaration, and thus the
+ property will be initialized with that empty object value.
+
+ Similarly, a colon in JavaScript can be either an object property value
+ assignment, or a code label. Thus, initializing a var property with an
+ object declaration can also require parentheses:
+
+ \qml
+ Item {
+ property var first: { example: 'true' } // example is interpreted as a label
+ property var second: ({ example: 'true' }) // example is interpreted as a property
+ property var third: { 'example': 'true' } // example is interpreted as a property
+ Component.onCompleted: {
+ console.log(first.example) // prints 'undefined', as "first" was assigned a string
+ console.log(second.example) // prints 'true'
+ console.log(third.example) // prints 'true'
+ }
+ }
+ \endqml
+
\section1 Using Scarce Resources with the var Type
A \c var type property can also hold an image or pixmap.