Ack

Ack validates data in Dart and Flutter. This branch documents 2.0.0-beta.3; see the migration guide for 1.x changes.

Core concepts

• Schemas define accepted boundary data and the Dart values it becomes.
• Parsing validates input; safeParse returns a result. Codecs also encode runtime values back to the boundary.
• Presence and null differ: optional permits omission, nullable permits null, and JsonMaybe preserves both states.
• Generation is optional: @Schemable turns schemas into models or hand-written classes into schemas, using one .g.dart part.
• Generated model constructors are unchecked; use parsing for untrusted input and JSON encoding for validated output.
• Native schemas export Draft-7; imported 2020-12 resources retain their dialect unless explicitly lowered.
• Adapters reuse schemas for Firebase AI, MCP inputs, and json_schema_builder; Ack still validates the data.

Start here

Install the version documented on this branch:

dart pub add ack:^2.0.0-beta.3

import 'package:ack/ack.dart';

final userSchema = Ack.object({
  'name': Ack.string().minLength(2),
  'nickname': Ack.string().optional().nullable(),
});

final result = userSchema.safeParse({'name': 'Ada'});
if (result.isOk) {
  print(result.getOrThrow());
} else {
  print(result.getError());
}

See installation for SDK requirements, model generation for @Schemable, and codecs for encoding and callback failure semantics.

Packages

Package	Purpose
ack	Runtime schemas, codecs, JSON Schema import/export, annotations
ack_generator	Models from schemas and schemas from classes
ack_firebase_ai	Firebase AI response JSON Schema maps
ack_json_schema_builder	Bidirectional json_schema_builder bridge
ack_mcp_dart	MCP input schemas and typed argument validation

Examples demonstrate the packages together.

Documentation and contributing

• Guides and the branch-local agent API index
• Architecture decisions: rationale and superseded choices
• CONTRIBUTING.md: setup, checks, and generator resource limits
• PUBLISHING.md: coordinated releases and tag-only publication
• SUPPORT.md, SECURITY.md, and Code of Conduct