core_model

Primitives a Dart application keeps re-deriving, extracted once and tested. No Flutter dependency: it runs under dart test, in an isolate, or in a CLI.

Lease: monotonic ownership over a shared resource

One lease guards one resource scope: a hardware session, a storage key, a composition of dependencies. An owner calls acquire() and keeps the handle; a new term invalidates every handle issued before it, so a stale owner's deferred work (a queued release, a late callback, a retry) becomes a no-op instead of tearing down the current owner's state.

final lease = Lease();

final handle = lease.acquire();
// ... later, on a path that may have been superseded:
lease.guard(handle, () => transport.close());

It is not a mutex: it serializes nothing, it decides whose completed work still counts.

CancelToken: cooperative cancellation

A token an operation checks, and a caller cancels. No timers, no zones, no Future wrapping.

RetryBackoff: exponential backoff with jitter

The retry schedule as a function, so a client's retry policy is a value that can be tested rather than a loop that has to be read.

Clock: the current instant as a dependency

Time an application records or acts on — an expiry, a scheduled reminder, the date a record is filed under — reached through an injected clock rather than a static call, so a caller can be handed one that reports an instant the calendar has not. SystemClock is the real one, and it reads UTC.

final class Entitlement {
  const Entitlement(this._clock);
  final Clock _clock;

  bool get expired => _expiresAt.isBefore(_clock.now());
}

// production
const Entitlement(SystemClock());

Presentation timing does not belong here: a tap window or a "2 h ago" label is about the frame in front of the user, not a fact being recorded.

DiTimings: what each start-up step cost

A diagnostics side-channel for a staged initialization, held statically and deliberately outside the container it measures the building of — whatever reports these timings has to work when initialization failed, and then there is no container left to read them from.

DiTimings.reset(); // a retry must not append to the attempt that failed
for (final step in steps) {
  final watch = Stopwatch()..start();
  await step.run();
  DiTimings.record(step.name, watch.elapsed);
}
// afterwards, including after a failure:
DiTimings.steps; // List<({String name, Duration duration})>, in order
DiTimings.total;

Also here

Guid, a UUID as a string with GuidX.nil and GuidX.empty; IDeviceInfo, the interface an application implements to describe the device and build it runs on; a platform-neutral VoidCallback typedef, so a package that uses it stays free of dart:ui; and RetryNotifier, the callback a retrying middleware reports each attempt through.

Install

dependencies:
  core_model: ^0.1.1

Changelog

CHANGELOG.md

License

MIT