A fluent, builder-based library for generating valid Dart code.
code_builder has a narrow and user-friendly API.
Most Dart syntax structures are created using builders. For example, an empty class:
final animal = Class((builder) => builder
..name = 'Animal'
..extend = refer('Organism')
);Will produce:
class Animal extends Organism {}If you're not a fan of nesting, you can create a builder directly and then call the build function. For example, adding a method to our class:
final method = MethodBuilder()
..name = 'eat'
..body = refer('print').call([literal('Yum!')]).statement // print('Yum!');
..lambda = true;
final animal = Class((builder) => builder
..name = 'Animal'
..extend = refer('Organism')
..methods.add(method.build()) // MethodBuilder -> Method
);Will produce:
class Animal extends Organism {
void eat() => print('Yum!');
}Then, when finished, use a DartEmitter and the accept method to build the code_builder structures into valid Dart code. For example:
import 'package:dart_style/dart_style.dart';
// ... //
final emitter = DartEmitter();
// Generate code for 'animal' into a new StringBuffer
final StringSink result = animal.accept(emitter);
// or, add it to an existing one
final buffer = StringBuffer();
animal.accept(emitter, buffer);
// format the output using package:dart_style
final String formatted = DartFormatter(
languageVersion: DartFormatter.latestLanguageVersion)
.format(result.toString());
// voilà
print(formatted);Will output the code from above.
For more usage examples see the example and test folders.
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')),
]));
// use a scoped DartEmitter to enable automatic prefixing
// using Allocator.simplePrefixing
final emitter = DartEmitter.scoped();
final formatted = DartFormatter(
languageVersion: DartFormatter.latestLanguageVersion)
.format(library.accept(emitter).toString());
print(formatted);
}Will output:
import 'package:a/a.dart' as _i1;
import 'package:b/b.dart' as _i2;
_i1.Thing doThing() {}
_i2.Other doOther() {}- Read and help us document common patterns over in the docs.
- Is there a bug in the code? File an issue.
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
dartfmtmust be used to format this repository. You can run it simply from the command-line:dart run dart_style:format -w .
NOTE: There is currently a limitation in
build_runnerthat 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.
./tool/regenerate.sh