A comprehensive guide to modern error handling in Dart/Flutter, covering four progressive patterns: Dart 3 Records as lightweight result containers, sealed AppResult types with compiler-enforced exhaustive handling, the Monad pattern with map/flatMap for chaining sequential operations, Either types via the dartz package, and typed sealed exceptions using Freezed. The article walks through a full clean architecture stack showing how each pattern fits a specific layer — records in the data layer, Either at boundaries, AppResult in the domain layer, and exhaustive pattern matching in the presentation layer — eliminating invisible failures and runtime surprises.
Table of contents
Table of ContentsPrerequisitesThe Problem with Exceptions in DartPart 1: Record Types as Lightweight Result ContainersPart 2: Building a Proper Sealed Result TypePart 3: Extending to the Monad PatternPart 4: Either with dartzPart 5: Typed Exceptions with FreezedPart 6: Putting It All TogetherConclusionSort: