Handle the error
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This document discusses errors in Swift. It covers topics like: - Any type can adopt the Error protocol in Swift - Functions, computed properties, and subscripts can throw errors - catch blocks can match patterns to catch errors - Common errors include ignoring errors or not handling them properly - Advanced topics include rethrowing errors, result equivalency, and different strategies for handling and responding to errors.
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Handle the error
- 1. @kamidude
- 2. @kamidude ERRORS types & debugging NSError conforms Error Error is convertible to NSError *
- 3. @kamidude STOPPING EXECUTION objc can @catch exceptions / swift cannot only fatalError is kept on -Ounchecked *
- 4. @kamidude SWIFT ERRORS * Every type can adopt Error basics - conforming
- 5. @kamidude SWIFT ERRORS Functions Only Computed Properties Subscript basics - throwing errors *
- 6. @kamidude SWIFT ERRORS basics - catching errors catch can match pattern swift errors are not exceptions ! *
- 7. @kamidude SWIFT ERRORS common error - ignoring errors * never ignore errors
- 8. @kamidude SWIFT ERRORS advanced - rethrowing non-throwing is a specific case of throwing func *
- 9. @kamidude SWIFT ERRORS advanced - result equivalency
- 10. @kamidude SWIFT ERRORS advanced - result equivalency
- 11. @kamidude SWIFT ERRORS advanced - result equivalency
- 12. @kamidude ERRORS handling strategies My own rules of thumb Adapt to your use case Expected Unexpected Domain • Handle in the application code • Display details to the user • Don’t log the error • Raise an error • Display details to the user • Log the error Technical • Handle in the application code • Don’t display details to the user • Don’t log the error • Raise an error • Don’t display details to the user • Log the error Domain vs Technical / Expected vs Unexpected http://www.blueskyline.com/ErrorPatterns/ErrorPatternsPaper.pdf
- 13. @kamidude ERRORS error semantic - handling strategies Retry Silently - Not a solution : if the retry fails, you have to handle the error eventually - Exponential backoff 👍 Easy 👎 Not a real solution My own rules of thumb Adapt to your use case
- 14. @kamidude ERRORS error semantic - handling strategies Ask user to retry / cancel - Modally or not - Basic strategy : prevent access to content 👍 Easy 👎 Poor UX My own rules of thumb Adapt to your use case
- 15. @kamidude ERRORS error semantic - handling strategies Optimistic update - Show updated local UI - Works for user actions, not fetching 👍 User friendly / works in most cases 👎 Involves complex synchronization / client logic My own rules of thumb Adapt to your use case
- 16. @kamidude ERRORS error semantic - handling strategies Crash - Intended or not 👍 Get info through CrashReporter & fix 👎 Not very user friendly My own rules of thumb Adapt to your use case