Zema

Schema validation for Dart, inspired by Zod.
Define schemas once, parse anywhere. All errors collected in a single pass.
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Zema is a type-safe schema validation library for Dart. Think Zod, but for Dart. Declare your data contracts once and reuse them across your whole application, whether it's parsing API responses, validating form inputs, or enforcing invariants at runtime.

# pubspec.yaml
dependencies:
  zema: ^0.6.0

import 'package:zema/zema.dart';

final userSchema = z.object({
  'name': z.string().min(2),
  'email': z.string().email(),
  'age': z.integer().gte(18).optional(),
});

// parse() returns the validated value or throws ZemaException
final user = userSchema.parse({
  'name': 'Alice',
  'email': 'alice@example.com',
});

// safeParse() never throws, returns ZemaResult<T>
final result = userSchema.safeParse(rawInput);

switch (result) {
  case ZemaSuccess(:final value):
    print(value['name']);
  case ZemaFailure(:final errors):
    for (final issue in errors) {
      print('${issue.path.join(".")}: ${issue.message}');
    }
}

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Packages

Package	Description	CI	Pub
zema	Core validation library
zema_forms	Flutter form widgets & controller
zema_firestore	Cloud Firestore integration via withConverter
zema_hive	Hive local storage integration
zema_standard_schema	Standard Schema adapter for CLI frameworks & consumers

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Why Zema?

• Exhaustive error collection. No short-circuiting. Every issue is found and reported in one pass.
• Composable. Schemas are just values. Combine, transform, and reuse them freely.
• Type-safe. Full Dart 3 type inference. What you validate is what you get.
• Fast. Competitive with hand-written validation. Benchmarks included.
• Immutable. Every method returns a new schema. No side effects, no surprises.

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Performance

Schemas defined once at the top level and reused, measured with benchmark_harness on an Apple M-series chip, Dart 3.x (JIT). Lower is better.

Scenario	zema	acanthis	zard	ez_validator	luthor
String.email	0.81 µs	1.80 µs	3.83 µs	0.78 µs	74.7 µs
Integer.range	0.17 µs	0.47 µs	2.13 µs	0.33 µs	0.62 µs
Object.flat (4 fields)	4.37 µs	4.34 µs	13.4 µs	10.1 µs	92.8 µs
Object.failure (3 errors)	12.8 µs	6.27 µs	68.0 µs	11.3 µs	40.2 µs

Object.failure measures exhaustive error collection across all fields simultaneously, a core feature of Zema. Libraries that short-circuit on the first error will appear faster on this specific scenario.

Run the benchmarks yourself: make bench

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Documentation

Full documentation is available at zema.meragix.dev.

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Contributing

Contributions are welcome! Head over to CONTRIBUTING.md to get started.

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License

This project is licensed under the MIT License. See the LICENSE file for details.