Stage 1 · Lesson 7 of 10
Exceptions and error handling
splits failures into two kinds. An Exception is a failure you expect and should handle, such as a FormatException from bad input. An Error is a programming mistake, such as a RangeError, that you fix rather than catch.
Learn try, on SomeException catch (e), finally and rethrow. Throw your own exception with a useful message. Catch where you can do something, such as showing a retry message, not in every function. code, which waits for results, has its own rule.
Common trapThe trap in async code is a Future that is never awaited: its error does not reach your try block at all and appears only as an unhandled error in the logs, if you look.
A question to check yourself, an AI practice session and 2 cheat sheet entries come with the full roadmap. Unlock
Resources for this stage
Start with
- GuideFreeDart Language Tour
Google · Beginner
The official tour: read it in order and rerun every example in DartPad