Deferreds — Lightning talk notes

  • Deferreds are values that might not exist yet
  • But callbacks are used for letting you know that values exist
  • Deferreds are objects — they can be passed about
  • Deferreds can be successful and fail — so we do not have to use sentinel values
  • Deferreds’ callback/errback can be chained
  • A failed callback/errback calls the next errback in the chain
  • A successful callback/errback calls the next callback in the chain
  • If you like being able to find your bugs finish your deferres with log.err
  • Use defer.succeed/ to make sure you’re always retunring the same type
  • Use maybeDeferred to make sure that your users are not paying for your infrastructure’s mistake

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