Dart / Contracts: patterns, generic APIs, and asynchronous results

Dart β€” Contracts: patterns, generic APIs, and asynchronous results

Develop structural and finite-choice models, runtime-aware generic boundaries, API reuse, Future ownership, and stream delivery contracts.

6 lessons Β· No account required

What you will learn

  • Preserve data meaning and lifecycle ownership across reusable and asynchronous boundaries.

  1. Use records and patterns to preserve data shape

    Return multiple values with records and match known shapes through destructuring, type patterns, guards, and switch expressions.

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  2. Model alternatives with sealed outcomes and enums

    Represent one valid outcome at a time and keep internal exhaustive handling separate from external-code compatibility.

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  3. Use generic types without unsafe write assumptions

    Preserve element types, choose meaningful bounds, and understand Dart covariance and runtime checks at mutable collection boundaries.

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  4. Choose API boundaries, mixins, and static extensions

    Distinguish implementation inheritance, interface contracts, reusable mixin behavior, and extension lookup under Dart library rules.

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  5. Own Future results, errors, and waiting semantics

    Use async and await with deliberate sequencing, early error observation, and truthful timeout or cancellation expectations.

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  6. Own stream subscriptions and delivery semantics

    Handle values, errors, completion, cancellation, and single-subscription or broadcast behavior without assuming replay or bounded buffering.

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