read static method

ProcessingState? read(
  1. String? appleValue
)

Apple's appleValue read as a member: unknown for a value this version does not name, null when Apple sent nothing.

The only place Apple's spellings are compared to anything. A switch case pattern must be a compile-time constant and processing.appleValue is not one, so code branching on the state used to switch on string literals — 'PROCESSING' written in the enum and again in every branch that cared. Reading to a member first makes those enum switches, which is one copy of each spelling and exhaustive.

Implementation

static ProcessingState? read(String? appleValue) => appleValue == null
    ? null
    : values.firstWhere(
        (s) => s.appleValue == appleValue,
        orElse: () => unknown,
      );