darto_validator 1.3.0

Request validation middleware for Darto powered by zard — a Zod-inspired schema library for Dart.

darto_validator

Request validation middleware for Darto, powered by zard — a Zod-inspired schema library for Dart.

For a generic validator without zard, use validator() from the core darto package.

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Install

dependencies:
  darto: ^1.0.0
  darto_validator: ^1.0.0

zard is re-exported from darto_validator, so no separate dependency is needed.

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Quick start

import 'package:darto/darto.dart';
import 'package:darto_validator/darto_validator.dart';

final userSchema = z.map({
  'name':  z.string().min(1),
  'email': z.string().email(),
  'age':   z.int().min(0).max(150),
});

void main() {
  final app = Darto();

  app.post('/users', [zValidator('json', userSchema)], (Context c) {
    final data = c.req.valid<Map<String, dynamic>>('json');
    return c.created({'user': data});
  });

  app.listen(3000);
}

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zValidator(target, schema, [hook])

Validates data from a specific part of the request against a zard schema and stores the coerced result for the handler.

Targets

Target	Source
'json'	Request body (application/json)
'query'	URL query string parameters
'param'	Route path parameters (e.g. /:id)
'form'	Form body (application/x-www-form-urlencoded or multipart/form-data)
'header'	Request headers

Retrieve in handler — c.req.valid<T>(target)

// JSON body
app.post('/users', [zValidator('json', userSchema)], (c) {
  final data = c.req.valid<Map<String, dynamic>>('json');
  return c.created({'user': data});
});

// Query params
app.get('/search', [zValidator('query', z.map({'q': z.string().min(1)}))], (c) {
  final q = c.req.valid<Map<String, dynamic>>('query');
  return c.ok({'query': q['q']});
});

// Route params
app.get('/posts/:id', [zValidator('param', z.map({'id': z.string()}))], (c) {
  final params = c.req.valid<Map<String, dynamic>>('param');
  return c.ok({'id': params['id']});
});

Hook — custom error handling

The optional third argument is called for every request — success or failure. Return a Response to short-circuit; return null to fall through to default behaviour.

app.post('/items', [
  zValidator('json', schema, (ZardResult result, c) {
    if (!result.success) {
      return c.status(422).json({
        'message': 'Unprocessable entity',
        'issues': result.error?.format(),
      });
    }
    return null; // let it continue
  }),
], handler);

Default error response (400)

When no hook is provided and validation fails:

{
  "error": "Validation failed",
  "target": "json",
  "issues": ["name: Required", "email: Invalid email"]
}

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Schema DSL (z)

z is re-exported directly from darto_validator:

import 'package:darto_validator/darto_validator.dart';

final schema = z.map({
  'name':    z.string().min(1).max(100),
  'email':   z.string().email(),
  'age':     z.int().min(0).max(150),
  'active':  z.bool(),
  'score':   z.double().min(0),
  'tags':    z.list(z.string()),
  'role':    z.enumerate(['admin', 'user', 'guest']),
});

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API reference

Symbol	Description
zValidator(target, schema, [hook])	Validation middleware — Hono zod-validator-style
c.req.valid<T>(target)	Retrieve validated data (from core darto)
z	Zard schema builder (re-exported)
ZardResult	Result type — .success, .data, .error
schema.toOpenApiSchema()	Convert a zard schema to an OpenAPI 3.1 Schema Object map

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OpenAPI integration

Reuse a zard schema for documentation: toOpenApiSchema() converts it to an OpenAPI 3.1 Schema Object map, ready for darto_openapi's Schema.raw(...).

import 'package:darto_openapi/darto_openapi.dart';

final userSchema = z.map({
  'name': z.string().min(2).max(50),
  'email': z.string().email(),
  'age': z.int().min(0).max(120).optional(),
});

api.post('/users',
  request: Req(json: Schema.raw(userSchema.toOpenApiSchema())),
  responses: {201: Res('Created')},
  handler: (c) => c.created(c.req.valid('json')),
);

It captures object shape + required, arrays, enums, nullability, defaults and unions, plus fine-grained constraints: minLength/maxLength, pattern, format (email, uri, uuid, date, time, date-time, ipv4, ipv6, hostname), minimum/maximum, multipleOf and minItems/maxItems. So one zard schema both validates requests and documents the API. Only arbitrary refine/ transform logic can't be represented in a schema and is omitted (it still validates at runtime). Requires zard: ^1.2.0.

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See also

• darto — core framework
• zard — schema library
• examples/example_middleware_validator — working example

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Support 💖

If you find Darto Validator useful, please consider supporting its development 🌟Buy Me a Coffee.🌟 Your support helps us improve the package and make it even better!