dataclass 0.3.0+1

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dataclass #

License Pub.dev Github Stars

@DataClass annotation used for dataclass_generator

The DataClass generator generates base class for your data class with methods:

  • equals (operator ==)
  • hashCode
  • toString
  • copyWith

Getting Started #

0. Add dependencies to pubspec.yaml #

dependencies:
  dataclass: latest_version
dev_dependencies:
  dataclass_generator: latest_version

1. Annotate your class with @dataClass #

The class should:

  • has only final fields
  • unnamed constructor with named parameters for all fields
@dataClass
class Car {
  final String name;
  final String manufacturer;
  final double price;

  Car({this.name, this.manufacturer, this.price});
}

2. Generate dataclass base class #

Run pub run build_runner build

Generated file

abstract class _$Car {
  const _$Car();

  String get name;
  String get manufacturer;
  double get price;
  bool operator ==(other) {
    if (identical(this, other)) return true;
    if (other is! Car) return false;

    return true &&
        this.name == other.name &&
        this.manufacturer == other.manufacturer &&
        this.price == other.price;
  }

  int get hashCode {
    return mapPropsToHashCode([name, manufacturer, price]);
  }

  String toString() {
    return 'Car <\'name\': ${this.name},\'manufacturer\': ${this.manufacturer},\'price\': ${this.price},>';
  }

  Car copyWith({String name, String manufacturer, double price}) {
    return Car(
      name: name ?? this.name,
      manufacturer: manufacturer ?? this.manufacturer,
      price: price ?? this.price,
    );
  }
}

3. Extend class with generated base class #

@dataClass
class Car extends _$Car {
  final String name;
  final String manufacturer;
  final double price;

  Car({this.name, this.manufacturer, this.price});
}

Collection equality


@dataClass
class Car extends _$Car {
  @Collection(deepEquality: true) // Short-hand: @Collection()
  final List<String> parts;

  const Car({this.parts});
}

FAQ #

  1. Why you didn't use extension methods?

As the docs says that:

It is a compile-time error if an extension:

  • Declares a member with the same basename as a member declared by Object (==, hashCode, toString, noSuchMethod, runtimeType). This applies to both static and instance member declarations.
  1. May I use generics?

Yes.

[0.3.0+1] #

  • Copy README from repository to dataclass directory

[0.3.0] - 2019/01/19 #

  • Add @Collection() annotation to use DeepCollectionEquality from collection package to compare collections
  • Add @dataClass shorthand for @DataClass()

[0.2.0] - 2019/12/25 #

  • enable usage of generic types, eg. Product<T>
  • BREAKING CHANGE: change generated class name from _Class to _$Class
  • move example to dataclass package directory

[0.1.0+1] - 2019/12/22 #

  • update README - badges

[0.1.0] - 2019/12/22 #

  • @DataClass() annotation used by dataclass_generator
  • mapPropsToHashCode from equatable package used by hashCode getter

example/lib/main.dart

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

Use this package as a library

1. Depend on it

Add this to your package's pubspec.yaml file:


dependencies:
  dataclass: ^0.3.0+1

2. Install it

You can install packages from the command line:

with pub:


$ pub get

with Flutter:


$ flutter pub get

Alternatively, your editor might support pub get or flutter pub get. Check the docs for your editor to learn more.

3. Import it

Now in your Dart code, you can use:


import 'package:dataclass/dataclass.dart';
  
Popularity:
Describes how popular the package is relative to other packages. [more]
70
Health:
Code health derived from static analysis. [more]
100
Maintenance:
Reflects how tidy and up-to-date the package is. [more]
100
Overall:
Weighted score of the above. [more]
85
Learn more about scoring.

We analyzed this package on Mar 24, 2020, and provided a score, details, and suggestions below. Analysis was completed with status completed using:

  • Dart: 2.7.1
  • pana: 0.13.6

Dependencies

Package Constraint Resolved Available
Direct dependencies
Dart SDK >=2.0.0 <3.0.0
collection >=1.14.0 <1.15.0 1.14.12