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# System prepended metadata

title: Errors blog notes

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# Errors blog notes

## Keypoints (chapters)

* Intro - recap from the last time.
  * Introduce sample with a required behavior and showcase data source mapping. 
  * Mention that its tedious to write it by hand, not prone to errors and all developers must think about it
  * Mention that this approach is library-independent
* Mapping on the retrofit CallAdapter layer
  * Explain what CallAdapter is and how to implement it. Explain CallAdapterFactory and CallAdapter
  * Implement our CallWithErrorHandling
  * Note that we can either move all domain related mapping to the mapException method or we still need to trycatch in data source and map our domain exceptions to different ones
* Create custom ExceptionMapper
  * Explain Invocation tag 
  * Create custom annotation with abstract class for ExceptionMapper
  * Use this to implement RecipeDetailExceptionMapping 
