Lightning Aura Components Developer Guide

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Introducing Aura Components
Quick Start
Creating Components
Component Names
Create Aura Components in the Developer Console
Create Aura Components Using Salesforce CLI
Component Markup
Component Namespace
Component Bundles
Component IDs
HTML in Components
CSS in Components
Component Attributes
Using Expressions
Component Composition
Component Body
Component Facets
Controlling Access
Using Object-Oriented Development
Favor Composition Over Inheritance
What is Inherited?
Inherited Component Attributes
Abstract Components
Interfaces
Marker Interfaces
Inheritance Rules
Best Practices for Conditional Markup
Aura Component Versioning for Managed Packages
Base Components with Minimum API Version Requirements
Validations for Aura Component Code
Using Labels
Localization
Working with Lightning Base Components
Supporting Accessibility
Writing Documentation for the Component Library
Using Components
Communicating with Events
Communicating Across the DOM with Lightning Message Service
Creating Apps
Styling Apps
Developing Secure Code
Using JavaScript
Working with Salesforce Data
Testing Components
Debugging
Performance
Reference
PDF

Interfaces

Interfaces define a component’s shape by defining attributes, events, or methods that any implementing component contains. To use an interface, a component must implement it. An interface can’t be used directly in markup.

An interface starts with the <aura:interface> tag, and can contain only these tags:

<aura:attribute>
This tag defines an attribute. An interface can have zero or more attributes.

To set the value of an attribute inherited from an interface, redefine the attribute in the sub component using <aura:attribute> and set the value in its default attribute. When you extend a component, you can use <aura:set> in a sub component to set the value of any attribute that’s inherited from the super component. However, this usage of <aura:set> doesn’t work for attributes inherited from an interface.

Note

<aura:registerEvent>
This tag registers an event that can be fired by a component that implements the interface. There’s no logic in the interface for firing the event. A component that implements the interface contains the code to fire the event.
<aura:method>
This tag defines a method as part of the API of a component that implements the interface. There’s no logic for the method in the interface. A component that implements the interface contains the method logic.

You can’t use markup, renderers, controllers, or anything else in an interface.

Implement an Interface

To implement an interface, set the implements system attribute in the <aura:component> tag to the name of the interface that you are implementing. For example:

<aura:component implements="mynamespace:myinterface" >

A component can implement an interface and extend another component.

<aura:component extends="ns1:cmp1" implements="ns2:intf1" >

An interface can extend multiple interfaces using a comma-separated list.

<aura:interface extends="ns:intf1,ns:int2" >

Since there are fewer restrictions on the content of abstract components, they are more common than interfaces. A component can implement multiple interfaces but can only extend one abstract component, so interfaces can be more useful for some design patterns.

Example

Here’s an example of an interface.

<aura:interface>
    <aura:attribute name="value" type="String"/>

    <aura:registerEvent name="onItemSelected" type="ui:response"
      description="The event fired when the user selects an item" />

    <aura:method name="methodFromInterface">
        <aura:attribute name="stringAttribute" type="String" default="default string"/>
    </aura:method>
</aura:interface>