---

name: Flutter Error Handling description: Functional error handling using Dartz and Either. metadata: labels: [error-handling, dartz, functional] triggers: files: ['lib/domain/', 'lib/infrastructure/'] keywords: [Either, fold, Left, Right, Failure, dartz]

Error Handling

Priority: P1 (HIGH)

Standardized functional error handling using dartz and freezed failures.

Implementation Guidelines

• Either Pattern: Return Either<Failure, T> from repositories. No exceptions in UI/BLoC.
• Failures: Define domain-specific failures using @freezed unions.
• Mapping: Infrastructure catches Exception and returns Left(Failure).
• Consumption: Use .fold(failure, success) in BLoC to emit corresponding states.
• Typed Errors: Use left(Failure()) and right(Value()) from Dartz.

Reference & Examples

For Failure definitions and API error mapping: See references/REFERENCE.md.

Related Topics

layer-based-clean-architecture | bloc-state-management