If you are developing a custom component, that can change value, chances are that it will need the adjustable accessibility trait (VoiceOver will say: "Adjustable"). Think of a component that lets you rate from one to five thumbs up (or stars).
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One thing I find very useful when testing (or doing demos!) is to have VoiceOver's caption panel enabled. It shows constantly at the bottom of the screen and you can see exactly what VoiceOver is saying.
In UIKit, to create an adjustable component we need to add the adjustable trait and override both accessibilityIncrement() and accessibilityDecrement(). In SwiftUI, everything you need is bundled in the accessibilityAdjustableAction(_:) modifier.
Toggles or UISwitches are often found separated from the label that precedes (and describes) them; with an unclear label; missing a value, trait, or hint; or even not being actionable at all.
