With the button trait VoiceOver will read “button” after the accessibility label and will indicate the user that, when focused, they can double tap anywhere on the screen to interact with it. UIButton has this trait by default.
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Accessibility Labels are not just for VoiceOver, and Accessibility User Input Labels are not just for Voice Control. The latter will also help Full Keyboard Access users to find elements on the screen by different names. Good API design!
Sometimes, buttons change meaning, for example when toggled. An example is a play button, tap it and it becomes a pause button. In such case, updating its accessibility label will be clearer than trying to convey the change with traits or values.
A common example where you need to manually configure the button accessibility trait is for some table/collection view cells. These tend to be “buttons” that perform an action, like playing music, or bring the user to a different screen.
