strint

Safe JSON models for Flutter — avoid UI crashes when the backend sends wrong types (e.g. int instead of String?). Generates freezed models with Safe* converters so mismatched types become null instead of throwing.

Problem

You expect String? dollarRate from the API but sometimes get int. Standard fromJson throws and the app crashes.

Solution

Define your model once (YAML or CreateModel), generate a freezed class that uses SafeString, SafeInt, etc. Wrong types are converted to null instead of crashing.

Usage

1. Add dependency

In your app’s pubspec.yaml:

dependencies:
  strint: <your path or version>
  freezed_annotation: ^2.4.0
  json_annotation: ^4.9.0

dev_dependencies:
  build_runner: ^2.4.0
  freezed: ^2.4.0
  json_serializable: ^6.7.0

2. Create a model file (one command flow)

Create a new Dart file, e.g. lib/models/my_model.dart, with a single CreateModel call:

CreateModel('MyModel', {'int?': 'id', 'String?': 'name'});

Then from your project root run:

dart run strint:generate lib/models

This will:

1. Find all .dart files in lib/models that contain CreateModel(...)
2. Replace each file with the full freezed class (with Safe* annotations)
3. Run build_runner to generate .freezed.dart and .g.dart

So one command both generates the model and runs the freezed generator.

3. Alternative: YAML config

Create strint_models.yaml in your project root:

ReportModel:
  id: int?
  dollar_rate: String?

Then run:

dart run strint:generate

This creates lib/models/report_model.dart (and others). Run build_runner yourself:

dart run build_runner build --delete-conflicting-outputs

Or use dart run strint:generate strint_models.yaml lib/models --build-runner to also run build_runner.

4. Or generate from code

import 'package:strint/strint.dart';

void main() {
  final code = CreateModel('ReportModel', {
    'int?': 'id',
    'String?': 'dollar_rate',
  });
  File('lib/models/report_model.dart').writeAsStringSync(code);
}

Then run build_runner as above.

Supported types

• int?, String?, double?, bool?, DateTime?
• Map? / Map<String, dynamic>?
• List<int>?, List<String>?, List<double>?, List<bool>?
• Nested models: ReportModel? → SafeObject(ReportModel.fromJson)

Generated example

From ReportModel with id: int? and dollar_rate: String? you get:

@freezed
class ReportModel with _$ReportModel {
  const factory ReportModel({
    @JsonKey(name: 'id') @SafeInt() int? id,
    @JsonKey(name: 'dollar_rate') @SafeString() String? dollarRate,
  }) = _$ReportModel;

  factory ReportModel.fromJson(Map<String, dynamic> json) =>
      _$ReportModelFromJson(json);
}

When the API sends "dollar_rate": 42, SafeString.fromJson returns null and the UI stays safe.

License

See LICENSE.