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A fluent, builder-based library for generating valid Dart code.


code_builder has a narrow and user-friendly API.

See the example and test folders for additional examples.

For example creating a class with a method:

import 'package:code_builder/code_builder.dart';
import 'package:dart_style/dart_style.dart';

void main() {
  final animal = Class((b) => b
    ..name = 'Animal'
    ..extend = refer('Organism')
    ..methods.add(Method.returnsVoid((b) => b
      ..name = 'eat'
      ..body = const Code("print('Yum!');"))));
  final emitter = DartEmitter();


class Animal extends Organism {
  void eat() => print('Yum!');

Have a complicated set of dependencies for your generated code? code_builder supports automatic scoping of your ASTs to automatically use prefixes to avoid symbol conflicts:

import 'package:code_builder/code_builder.dart';
import 'package:dart_style/dart_style.dart';

void main() {
  final library = Library((b) => b.body.addAll([
        Method((b) => b
          ..body = const Code('')
          ..name = 'doThing'
          ..returns = refer('Thing', 'package:a/a.dart')),
        Method((b) => b
          ..body = const Code('')
          ..name = 'doOther'
          ..returns = refer('Other', 'package:b/b.dart')),
  final emitter = DartEmitter.scoped();


import 'package:a/a.dart' as _i1;
import 'package:b/b.dart' as _i2;

_i1.Thing doThing() {}
_i2.Other doOther() {}


If a feature is missing (the Dart language is always evolving) or you'd like an easier or better way to do something, consider opening a pull request. You can always file an issue, but generally speaking, feature requests will be on a best-effort basis.

NOTE: Due to the evolving Dart SDK the local dartfmt must be used to format this repository. You can run it simply from the command-line:

$ dart run dart_style:format -w .

Updating generated (.g.dart) files

NOTE: There is currently a limitation in build_runner that requires a workaround for developing this package since it is a dependency of the build system.

Make a snapshot of the generated build_runner build script and run from the snapshot instead of from source to avoid problems with deleted files. These steps must be run without deleting the source files.