Dastagir Ahmed

3 REAL-WORLD USES OF DART FACTORY CONSTRUCTORS

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Mobile App Engineering

FACTORY CONSTRUCTORS

in Dart give you control over how and when objects are created.

You're not just instantiating—you're designing clean, testable, future-proof code.

SINGLETON PATTERN

class AppConfig {
  static final AppConfig _instance = AppConfig._internal();
  factory AppConfig() => _instance;
  AppConfig._internal();
}
Avoid unnecessary object creation
Ensure one shared instance across your app
Used for Controllers and Providers

DYNAMIC PARSING

Parse dynamic JSON into different models

factory Animal.fromJson(Map<String, dynamic> json) {
  switch (json['type']) {
    case 'dog': return Dog(json['name']);
    case 'cat': return Cat(json['name']);
    default: throw UnimplementedError();
  }
}
Great for APIs
Keeps code DRY
Hides internal logic

SMART CACHING OR MEMOIZATION

factory ColorHex(String code) {
  return _cache.putIfAbsent(code, () => ColorHex._internal(code));
}
Improves performance
Reduces GC pressure
Keeps logic centralized

SUMMARY

Factory constructors = Power + Flexibility

Subclassing
Reuse
Validation
Testing
Memory safety

Start using them where they count.

Dastagir Ahmed

Full Stack Engineer

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