Component is missing a required property

This warning category is spelled [required] by qmllint.

Component is missing a required property

What happened?

The required property of a component was not set.

Why is this bad?

QML applications where components miss required properties will misbehave: they will not start at all if a missing required property is detected statically. Dynamically created components with missing required properties will not be created at runtime: they will be null instead.

Example

 import QtQuick

 Item {
     component RepeatMe: Item {
         required property int index;
         required property int helloWorld;
     }

     RepeatMe {} // not ok: required properties index and helloWorld not set

     Repeater {
         model: 10
         RepeatMe {} // not ok: required property index set by Repeater, but not helloWorld
     }
 }

To fix this warning, set the required properties:

 import QtQuick

 Item {
     component RepeatMe: Item {
         required property int index;
         required property int helloWorld;
     }

     RepeatMe {
         index: 0
         helloWorld: 42
     } // ok: all required properties were set

     Repeater {
         model: 10
         RepeatMe {
             helloWorld: index * 2 + 1
         } // ok: all required properties were set: index by the Repeater and helloWorld by the user
     }
 }