When building custom components, or if not relying on UIControl's attributes to configure state, it can be easy to forget to specify the right accessibility traits. These are indispensable for a good experience with VoiceOver, Switch Control...
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In Objective-C accessibility traits are a bitmask. Some devs find tricky to work with them using bitwise operations. In Swift they conform to the OptionSet protocol that conforms to SetAlgebra. That means you can simply insert/remove traits.
By its name, I misunderstood what shouldGroupAccessibilityChildren does the first time I saw it. It can be used for VoiceOver to traverse all items in a view before moving to the next one, instead of grouping as in combining those elements. VoiceOver traverses elements in the natural reading order, from left to right, top to bottom, in left-to-right languages. Sometimes data is displayed in columns, so that order might not be the most logical one. https://developer.apple.com/documentation/objectivec/nsobject-swift.class/shouldgroupaccessibilitychildren
Custom actions work with VoiceOver, Switch Control and Full Keyboard Access. They also do for Voice Control. You can say "Show actions for <item name/number>", and an action sheet with all options, numbered, will be presented to the user. For some use-cases, Voice Control users might not feel it is a big win. Navigation is not as big of an issue, and interacting with custom actions might be a bit trickier than with "exposed" buttons. But lots of times seems a fair compromise.
