Specifying Dynamic Properties

Each predefined QML type has a set of predefined properties that you can specify values for. You can add custom properties that would not otherwise exist for a particular type. You bind the properties to dynamic expressions to define global properties for an object that can be read by other objects. For example, you can specify global properties for the root object that you can use in the child objects.

For example, to specify spacing between UI elements, you could define a margin for an object of a QML type that does not have a margin property, and then use bindings to refer to the value of the margin property from other objects.

Similarly, you can add custom properties for your own QML types that are based on the predefined types.

You can add properties for objects in the Connections view, Properties tab.

"Custom properties in Connection View Custom Properties tab"

To add properties for an object:

  1. Select View > Views > Connections View > Properties.
  2. Select the (Add) button to add a dynamic property for the currently selected item. The item ID is displayed in the Item column.
  3. Double-click the value in the Property column to give a name to the property. Property names must begin with a lower case letter and can only contain letters, numbers, and underscores. JavaScript reserved words are not valid property names.
  4. Double-click the value in the Property Type column to specify the type of the property.
  5. Double-click the value in the Property Value column to specify the value of the property.

Right-click a property and select Open Binding Editor in the context menu to bind the value of the property to that of another one or to data accessible in the application in Binding Editor. For more information, see Setting Bindings.

"Binding Editor"

The properties you add for a QML type are displayed in the Properties view when you select a component of that type in Navigator or Form Editor.

"Custom properties in Properties view"

For more information about setting property values in the Properties view, see Specifying Item Properties.

For an example of using custom properties in an application, see Creating a Mobile Application.

Supported Property Types

The following table describes the supported property types:

aliasProperty alias that holds a reference to another property
boolBinary true or false value
colorColor value that can be specified by using an SVG color name, such as "red", "green", or "lightsteelblue", or a hexadecimal triplet or quad in the form "#RRGGBB" and "#AARRGGBB", respectively. For example, the color red corresponds to a triplet of "#FF0000" and a slightly transparent blue to a quad of "#800000FF". In addition, you can use the following Qt functions: Qt.rgba(), Qt.hsva(), Qt.hsla(), Qt.darker(), Qt.lighter(), and Qt.tint().
intWhole integer number, such as 0, 10, or -20
realNumber with a decimal point
stringFree form text string
urlResource locator, such as a file name. It can be either absolute, (http://qt-project.org), or relative (pics/logo.png). A relative URL is resolved relative to the URL of the parent component.
variantGeneric property type. For example, variant properties can store numbers, strings, objects, arrays, and functions.

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