Check out the following Dart code examples ranging from Dart unit testing to converting Dart to JavaScript snippets. When you add these Dart snippets to Pieces you can use them in your IDE for some extreme time-savers.
We had some of our team members share their most useful Dart snippets. These Dart sample code snippets are great for any developer to improve their workflow. Additionally, we added some general-purpose snippets that we think some may just find helpful!
Dart unit testing
Tags: dart, unit tests
Create a group of dart unit tests.
group('group of tests', () {
test('unit test', () {
expect(true, true);
});
});
Related links:
- How to write unit tests
- Dart test package
Copy files from Dart Package
Tags: dart, files, dart package
Uses Dart packaging URI to get the path to a package allowing one to pull assets/files from a Dart package. This ultimately allows “Flutter-like” asset bundling within a Dart package.
import 'dart:isolate';
var resolvedUri = await Isolate.resolvePackageUri(Uri(scheme: 'package', path: 'my_package/src/assets/cool_image.jpg'));
Related links:
- How to determine the Dart directory which a file is being executed
- How to find file in your Dart package
Dart Singleton example
Tags: dart, singleton, pattern, object oriented
Create a singleton class structure in Dart to ensure only one instance of a class is created. This can be used to update properties, enhance performance, and manage state.
class SingletonClass {
static final SingletonClass _instance = SingletonClass._internal();
factory SingletonClass() {
return _instance;
}
SingletonClass._internal();
String property1 = 'Default Property 1';
String property2 = 'Default Property 2';
}
/// Example consuming the singleton class and accessing/manipulating properties
/// To evaluate the difference between a normal class and a singleton class, comment
/// out the factory constructor and _instance in SingletonClass and re-run.
void main() {
/// Properties before
String property1Before = SingletonClass().property1;
String property2Before = SingletonClass().property2;
print('property1Before: $property1Before'); // Default Property 1
print('property2Before: $property2Before'); // Default Property 2
/// Updating the properties
SingletonClass().property1 = 'Updated Property 1';
SingletonClass().property2 = 'Updated Property 2';
/// Properties after
print('property1After: ${SingletonClass().property1}'); // Updated Property 1
print('property2After: ${SingletonClass().property2}'); // Updated Property 2
}
Related links:
- How to build a Singleton in Dart
How to convert an object to JSON
Tags: dart, JSON, object to JSON
This Dart code sample will convert an object into a JSON string.
import 'dart:convert';
JsonEncoder().convert(yourObject)
Related links:
- Dart examples code for a JsonEncoder class
- Dart code for JsonEncoder constructor
How to convert JSON to an Object
Tags: dart, JSON, object
Converts JSON into an object.
import 'dart:convert';
JsonDecoder().convert(yourJson)
Related links:
- How to decode a Json file in Flutter
- JsonDecoder class - sample Dart code
- Dart code example to decode a Json file in flutter
How to create a Dart data class
Tags: dart, data class
Creates a data class.
@immutable
class User {
final String name;
final int age;
User(this.name, this.age);
User copyWith({
String name,
int age,
}) {
return User(
name ?? this.name,
age ?? this.age,
);
}
@override
bool operator ==(Object o) {
if (identical(this, o)) return true;
return o is User && o.name == name && o.age == age;
}
@override
int get hashCode => name.hashCode ^ age.hashCode;
}
Related links:
- How to create a immutable class
- Understanding data classes - IBM documentation
How to call a conditional function using Dart source code
Tags: dart, conditional function
Calls function depending on conditional values.
void func1(){
print("func 1 called");
}
void func2(){
print("func 2 called");
}
void main() {
const someValue = 3;
(someValue == 4? func1 : func2)();
}
Related links:
- How to call a function in a condition - Dart Flutter
- Dart conditional operators
How to remove falsy values in Dart
Tags: dart, remove falsy
Calls function depending on conditional values.
List compact(List lst) {
return lst..removeWhere((v) => [null, false].contains(v));
}
Related links:
- Remove empty and fasly values from a List - Dart code examples
- Best way to filter null from a list using Dart coding language
How to find difference of lists
Tags: dart, difference, lists
Finds the difference between two lists.
List difference(Iterable a, Iterable b) {
final s = b.toSet();
return a.where((x) => !s.contains(x)).toList();
}
Related links:
- Different ways to check differences between two lists with Dart code examples
- Get difference of list - flutter Dart
How to find Intersection using Dart source code
Tags: dart, list, intersection
Finds elements that exist in two lists.
main() {
final lists = [
[1, 2, 3, 55, 7, 99, 21],
[1, 4, 7, 65, 99, 20, 21],
[0, 2, 6, 7, 21, 99, 26]
];
final commonElements =
lists.fold(
lists.first.toSet(),
(a, b) => a.intersection(b.toSet()));
print(commonElements);
}
Related links:
- toSet Method - Dart Snippets
- How to extract common elements from a list in Dart
How to Flatten a list in Dart
Tags: dart, flatten
Flatten a multi-dimensional list into a one-dimensional one.
List flatten(List lst) {
return lst.expand((e) => e is List ? flatten(e) : [e]).toList();
}
Related links:
- Dart recursion
- How to flatten a list
Has truthy value
Tags: dart, truthy
Returns true if one element in a collection has a truthy value based on a predicate function.
bool some(Iterable itr, bool Function(T) fn) {
return itr.any(fn);
}
Related links:
- Any Method - Iterable class
- Difference between any and every in Dart
Dart Syntax highlighting
Tags: dart, flutter, syntax highlight, StatelessWidget
These Dart code samples display code with syntax highlighting in a flutter app.
import 'package:flutter/material.dart';
import 'package:flutter_highlight/flutter_highlight.dart';
import 'package:flutter_highlight/themes/github.dart';
class MyWidget extends StatelessWidget {
@override
Widget build(BuildContext context) {
var code = '''main() {
print("Hello, World!");
}
''';
return HighlightView(
// The original code to be highlighted
code,
// Specify language
// It is recommended to give it a value for performance
language: 'dart',
// Specify highlight theme
// All available themes are listed in `themes` folder
theme: githubTheme,
// Specify padding
padding: EdgeInsets.all(12),
// Specify text style
textStyle: TextStyle(
fontFamily: 'My awesome monospace font',
fontSize: 16,
),
);
}
}
Related links:
- Flutter highlight widget
How to copy directory and files recursively
Tags: dart, directory, directory and files
Copies a directory (source) and all of its contents recursively to a new directory (destination)
import 'dart:io';
import 'package:path/path.dart' as path;
Future copyDirectoryRecursive(Directory source, Directory destination) async {
await for (var entity in source.list(recursive: false)) {
if (entity is Directory) {
var newDirectory =
Directory(p.join(destination.absolute.path, p.basename(entity.path)));
await newDirectory.create();
await copyDirectory(entity.absolute, newDirectory);
} else if (entity is File) {
await entity.copy(p.join(destination.path, p.basename(entity.path)));
}
}
}
// HOW TO USE IT:
// await copyDirectoryRecursive(Directory('cool_pics/tests'), Directory('new_pics/copy/new'));
Related links:
- Built-in function to copy a directory in Dart
How to create terminal console color
Tags: dart, console, console messages, console colors
Add colors like red, green, and blue to terminal output.
import 'dart:io';
import 'package:colorize/colorize.dart';
class Messages {
// Prints
static void printGood(String message) => print(Colorize(message).green());
static void printWarning(String message) => print(Colorize(message).red());
static void printInfo(String message) => print(Colorize(message).blue());
// Stdouts
static void outGood(String message) => stdout.write(Colorize(message).green());
static void outWarning(String message) => stdout.write(Colorize(message).red());
static void outInfo(String message) => stdout.write(Colorize(message).blue());
// Returned colored strings
static String good(String message) => Colorize(message).green().toString();
static String warning(String message) => Colorize(message).red().toString();
static String info(String message) => Colorize(message).blue().toString();
}
Related links:
- Color console output
Convert Dart to JavaScript
Tags: dart, dart to javascript, dart export
Transpile methods from Dart to JavaScript and tries calling the Dart methods that have been transpiled.
import 'package:js/js.dart';
import 'package:node_interop/node.dart';
void main() {
setExport('hello', allowInterop(hello));
setExport('numbers', allowInterop(numbers));
setExport('circles', allowInterop(circles));
}
String hello() {
return 'Hello hoomans!';
}
String numbers() {
return 'test string';
}
String circles() {
return 'second test';
}
}
Related links:
- Dart interfaces for JavaScript APIs
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