Classes (ux:Class)

The ux:Class attribute defines a new UX (Uno) class where the type of the XML element is the base class. This means the new class inherits all public properties, events and behaviors from the superclass.

Any tree of UX Markup elements can easily be converted into a component using the ux:Class attribute. Classes can contain JavaScript tags that manages the inner business logic of the component.


<base_class ux:Class="class_name" />

Where base_class is any class accesible to UX Markup, and class_name is a fully qualified class name (including namespace path, if desired, separated by .).


The following example defines a new class MyCheckBox which is blue while unchecked, and red while checked. Tapping the checkbox changes the state.

<Panel ux:Class="MyCheckBox" Color="Blue">
    <bool ux:Property="Value" />

        function toggle() {
            this.Value.value = !this.Value.value;

        module.exports = { toggle: toggle };

    <WhileTrue Value="{Property Value}" />
        <Change this.Color="Red" Duration="0.2" />
        <Callback Handler="{toggle}" />

Why use classes?

Fuse encourages breaking your app into components (classes) for several reasons:

  • Good practice - Component-orientation keeps your code base clean, testable, scaleable and easy to maintain.
  • Reuse - It is useful to create components to allow reusing pieces of UI and logic in multiple places.
  • Styling - Creating new classes based on primitives is the recommended way to create a consistent look and feel throughout your project.

InnerClass (ux:InnerClass)

ux:InnerClass is a special version of ux:Class. Just like ux:Class, it also defines a new UX (Uno) class and inherits all the properties of the base class. The special thing about ux:InnerClass is that it has access to the names of its parent scope. This also means that you can only create instances of it inside its parent scope.

Note: InnerClass can seem like a very convenient feature at first glance, but you should be careful about using it as it can lead to tight coupling of components. Its usually a good idea to stick with ux:Class in most situations.


<base_class ux:InnerClass="class_name" />


In the following example, notice that we access toggleStatusPanel which is defined outside of our class definition of MyInnerClass. We can do this because we declare it using ux:InnerClass instead of ux:Class.

        <Panel ux:Name="statusPanel" Color="#f00" Height="80" Dock="Top" />
        <WhileTrue ux:Name="toggleStatusPanel">
            <Change statusPanel.Color="#0f0" />
        <Panel ux:InnerClass="MyInnerClass" Height="80" Color="Blue" Margin="5">
                <Toggle Target="toggleStatusPanel" />
            <MyInnerClass />
            <MyInnerClass />
            <MyInnerClass />
            <MyInnerClass />


Note that ux:InnerClass covers a very special case of componentization in Fuse and should generally not be needed. Prefer creating an explicit interface in and out of your components using ux:Property and ux:Dependency.