dart

Dart: Idiomatic Efficiency Reference

When to Use

• Use this skill when the task matches this description: Language-specific super-code guidelines for dart.

Table of Contents

1. [Null Safety](#nulls)
2. [Collections & Iteration](#collections)
3. [Classes & Records](#classes)
4. [Async/Await & Streams](#async)
5. [Error Handling](#errors)
6. [Flutter-Specific Patterns](#flutter)
7. [Anti-patterns specific to Dart](#antipatterns)

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1. Null Safety {#nulls}

// ❌ Manual null check
String display;
if (user.name != null) {
  display = user.name!;
} else {
  display = 'Unknown';
}

// ✅
final display = user.name ?? 'Unknown';

// ❌ Nested null checks
if (user != null && user.address != null && user.address!.city != null) {
  print(user.address!.city!);
}

// ✅
final city = user?.address?.city;
if (city != null) print(city);

// ❌ Late field when nullable is correct
late String name; // crashes if accessed before assignment

// ✅ — use late only when you guarantee initialization before access
String? name; // honestly nullable
// late is fine for: late final _controller = TextEditingController();

// ❌ Bang operator (!) everywhere
final name = user.name!;
final city = user.address!.city!;

// ✅ — promote through null checks
final name = user.name;
if (name == null) return;
// name is now non-null (promoted)

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2. Col