applying-effective-dart

Dart 3 Latest Features and Effective Dart Best Practices Guide

Goal

Covers Dart 3 features (through 3.10) and Effective Dart practices for writing safe, maintainable code.

Instructions

1. Dart 3 Features

1.1 Records

Records aggregate multiple typed values without requiring a dedicated class.

• Best Practices:
  • Multiple Return Values: Prefer Records over throwaway wrapper classes.
  • Named Fields: Use named fields when returning more than two values or when semantics are ambiguous.

  // ✅ Recommended Usage
  ({double lat, double lon}) getLocation(String city) {
    return (lat: 25.0330, lon: 121.5654);
  }
  

1.2 Patterns and Destructuring

Patterns match and destructure data from Records, Lists, Maps, and custom objects.

• Best Practices:
  • Destructuring on declaration: Extract values from Records or Lists directly at assignment.
  • Replace complex if-statements: Use if-case to validate shape and extract variables simultaneously.

  // ✅ Recommended Usage
  final json = {'user': ['Zack', 25]};
  if (json case {'user': [String name, int age]}) {
    print('User $name is $age years old.');
  }
  

1.3 switch Expressions and Exhaustive Checking

switch expressions return values and provide compile-time exhaustiveness for sealed classes and enums.

• Best Practices:
  • Use as expression: Assign diverging values concisely with switch expressions.
  • Omit default: On sealed/enum types, omit default so the compiler catches unhandled cases when new variants are added.

1.4 Class Modifiers

Dart 3 class modifiers control inheritance and implementation boundaries.

• Best Practices:
  • sealed: For Algebraic Data Types (ADTs). Enables exhaustive switch checking. Ideal for State or Result/Error types.
  • interface: Allows implements only; prevents extends.
  • final: Prevents both extends and implements from external libraries.

1.5 Wildcard Variables — Dart 3.7

Local variables and parameters named _ are now non-binding — they can be declared multiple times without name collision, and their value cannot be read.