来学习了解下Flutter及Dart 编码规范？

✅
class SliderMenu { ... }

class HttpRequest { ... }

typedef Predicate<T> = bool Function(T value);

✅

class Foo {
  const Foo([arg]);
}

@Foo(anArg)
class A { ... }

@Foo()
class B { ... }

✅

const foo = Foo();

@foo
class C { ... }

✅

library peg_parser.source_scanner;

import 'file_system.dart';
import 'slider_menu.dart';

❌

library pegparser.SourceScanner;

import 'file-system.dart';
import 'SliderMenu.dart';

✅

import 'dart:math' as math;
import 'package:angular_components/angular_components'
    as angular_components;
import 'package:js/js.dart' as js;

❌

import 'dart:math' as Math;
import 'package:angular_components/angular_components'
    as angularComponents;
import 'package:js/js.dart' as JS;

✅

var item;

HttpRequest httpRequest;

void align(bool clearItems) {
  // ...
}

✅

const pi = 3.14;
const defaultTimeout = 1000;
final urlScheme = RegExp('^([a-z]+):');

class Dice {
  static final numberGenerator = Random();
}

❌

const PI = 3.14;
const DefaultTimeout = 1000;
final URL_SCHEME = RegExp('^([a-z]+):');

class Dice {
  static final NUMBER_GENERATOR = Random();
}

✅

if (arg == null) return defaultValue;

✅

if (overflowChars != other.overflowChars) {
  return overflowChars < other.overflowChars;
}

❌

if (overflowChars != other.overflowChars)
  return overflowChars < other.overflowChars;

✅

/// The number of characters in this chunk when unsplit.
int get length => ...

❌

// The number of characters in this chunk when unsplit.
int get length => ...

✅

/// Deletes the file at [path] from the file system.
void delete(String path) {
  ...
}

❌

/// Depending on the state of the file system and the user's permissions,
/// certain operations may or may not be possible. If there is no file at
/// [path] or it can't be accessed, this function throws either [IOError]
/// or [PermissionError], respectively. Otherwise, this deletes the file.
void delete(String path) {
  ...
}

✅

/// Deletes the file at [path].
///
/// Throws an [IOError] if the file could not be found. Throws a
/// [PermissionError] if the file is present but could not be deleted.
void delete(String path) {
  ...
}

❌

/// Deletes the file at [path]. Throws an [IOError] if the file could not
/// be found. Throws a [PermissionError] if the file is present but could
/// not be deleted.
void delete(String path) {
  ...
}

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/// Defines a flag with the given name and abbreviation.
///
/// @param name The name of the flag.
/// @param abbr The abbreviation for the flag.
/// @returns The new flag.
/// @throws ArgumentError If there is already an option with
///     the given name or abbreviation.
Flag addFlag(String name, String abbr) => ...

✅

/// Defines a flag.
///
/// Throws an [ArgumentError] if there is already an option named [name] or
/// there is already an option using abbreviation [abbr]. Returns the new flag.
Flag addFlag(String name, String abbr) => ...

my_package
└─ lib
   ├─ src
   │  └─ utils.dart
   └─ api.dart

✅

import 'src/utils.dart';

❌

import 'package:my_package/src/utils.dart';

❌

if (optionalThing?.isEnabled) {
  print("Have enabled thing.");
}

✅

// 如果为空的时候你想返回false的话:
optionalThing?.isEnabled ?? false;

// 如果为空的时候你想返回ture的话:
optionalThing?.isEnabled ?? true;

❌

optionalThing?.isEnabled == true;

optionalThing?.isEnabled == false;

✅

raiseAlarm(
    'ERROR: Parts of the spaceship are on fire. Other '
    'parts are overrun by martians. Unclear which are which.');

❌

raiseAlarm('ERROR: Parts of the spaceship are on fire. Other ' +
    'parts are overrun by martians. Unclear which are which.');

✅

'Hello, $name! You are ${year - birth} years old.';

❌

'Hello, ' + name + '! You are ' + (year - birth).toString() + ' y...';

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var points = [];
var addresses = {};

❌

var points = List();
var addresses = Map();

✅

var points = <Point>[];
var addresses = <String, Address>{};

❌

var points = List<Point>();
var addresses = Map<String, Address>();

✅

if (lunchBox.isEmpty) return 'so hungry...';
if (words.isNotEmpty) return words.join(' ');

❌

if (lunchBox.length == 0) return 'so hungry...';
if (!words.isEmpty) return words.join(' ');

var aquaticNames = animals
    .where((animal) => animal.isAquatic)
    .map((animal) => animal.name);

✅

for (var person in people) {
  ...
}

❌

people.forEach((person) {
  ...
});

✅

// 创建一个List<int>:
var iterable = [1, 2, 3];

// 输出"List<int>":
print(iterable.toList().runtimeType);

❌

// 创建一个List<int>:
var iterable = [1, 2, 3];

// 输出"List<dynamic>":
print(List.from(iterable).runtimeType);

❌

var objects = [1, "a", 2, "b", 3];
var ints = objects.where((e) => e is int);

❌

var objects = [1, "a", 2, "b", 3];
var ints = objects.where((e) => e is int).cast<int>();

✅

var objects = [1, "a", 2, "b", 3];
var ints = objects.whereType<int>();

✅

void insert(Object item, {int at = 0}) { ... }

❌

void insert(Object item, {int at: 0}) { ... }

✅

void error([String message]) {
  stderr.write(message ?? '\n');
}

❌

void error([String message = null]) {
  stderr.write(message ?? '\n');
}

❌

class Circle {
  num _radius;
  num get radius => _radius;
  set radius(num value) {
    _radius = value;
    _recalculate();
  }

  num _area;
  num get area => _area;

  num _circumference;
  num get circumference => _circumference;

  Circle(this._radius) {
    _recalculate();
  }

  void _recalculate() {
    _area = pi * _radius * _radius;
    _circumference = pi * 2.0 * _radius;
  }
}

✅

class Circle {
  num radius;

  Circle(this.radius);

  num get area => pi * radius * radius;
  num get circumference => pi * 2.0 * radius;
}

✅

class Box {
  var contents;
}

❌

class Box {
  var _contents;
  get contents => _contents;
  set contents(value) {
    _contents = value;
  }
}

❌

class Point {
  num x, y;
  Point(num x, num y) {
    this.x = x;
    this.y = y;
  }
}

✅

class Point {
  num x, y;
  Point(this.x, this.y);
}

✅

Widget build(BuildContext context) {
  return Row(
    children: [
      RaisedButton(
        child: Text('Increment'),
      ),
      Text('Click!'),
    ],
  );
}

❌

Widget build(BuildContext context) {
  return new Row(
    children: [
      new RaisedButton(
        child: new Text('Increment'),
      ),
      new Text('Click!'),
    ],
  );
}

✅

const primaryColors = [
  Color("red", [255, 0, 0]),
  Color("green", [0, 255, 0]),
  Color("blue", [0, 0, 255]),
];

❌

const primaryColors = const [
  const Color("red", const [255, 0, 0]),
  const Color("green", const [0, 255, 0]),
  const Color("blue", const [0, 0, 255]),
];

❌

try {
  somethingRisky();
} catch (e) {
  if (!canHandle(e)) throw e;
  handle(e);
}

✅

try {
  somethingRisky();
} catch (e) {
  if (!canHandle(e)) rethrow;
  handle(e);
}

✅

var buffer = StringBuffer()
  ..write('one')
  ..write('two')
  ..write('three');

❌

var buffer = StringBuffer()
    .write('one')
    .write('two')
    .write('three');

✅

Future<int> triple(FutureOr<int> value) async => (await value) * 3;

❌

FutureOr<int> triple(FutureOr<int> value) {
  if (value is int) return value * 3;
  return (value as Future<int>).then((v) => v * 3);
}

❌

new Task(true);
new Task(false);
new ListBox(false, true, true);
new Button(false);

✅

Task.oneShot();
Task.repeating();
ListBox(scroll: true, showScrollbars: true);
Button(ButtonState.enabled);

✅

class Person {
  final String name;
  // ···
  bool operator ==(other) => other is Person && name == other.name;

  int get hashCode => name.hashCode;
}

❌

class Person {
  final String name;
  // ···
  bool operator ==(other) => other != null && ...
}