Function Select

@Select decorator works similarly to the Choice decorator but the function passed as argument directly returns the Primitive instead of declaring the condition.

The @Select decorator should be used for a small subset of special cases, most of the time the @Choice decorator fits the job perfectly. But sometimes certain format definitions have a long list of sub type you need match to a set of value and defining every available options in the @Choice decorator is verbose.

At the end of the day use the one you feel make your definition easier to read in your declaration, both are valid options.

const DEFINITION = {
   0: {
     1: SubProtocol,
     ...
   },
   ...
}

class SubProtocol {
}

class Protocol {
  @Relation(PrimitiveType.u8)
  foo: number

  @Relation(PrimitiveType.u8)
  bar: number

  @Select(_ => DEFINITION[_.foo][_.bar])
  sub_protocol
}
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