Component Attributes

Use the <aura:attribute> tag to add an attribute to the component or app. Let’s look at the following sample, helloAttributes.app:

1swfobject.registerObject("clippy.codeblock-0", "9");
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17<aura:application>
18    <aura:attribute name="whom" type="String" default="world"/>
19    Hello {!v.whom}!
20</aura:application>
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All attributes have a name and a type. Attributes may be marked as required by specifying required="true", and may also specify a default value.

In this case we've got an attribute named whom of type String. If no value is specified, it defaults to "world".

Though not a strict requirement, <aura:attribute> tags are usually the first things listed in a component’s markup, as it provides an easy way to read the component's shape at a glance.

Attribute names must start with a letter or underscore. They can also contain numbers or hyphens after the first character.

Now, append ?whom=you to the URL and reload the page. The value in the query string sets the value of the whom attribute. Supplying attribute values via the query string when requesting a component is one way to set the attributes on that component.