const constructor

Learn how const constructor improves performance.

const constructor

Marking a constructor const lets Flutter merge all instances created with the same parameters into a single canonical object. This reduces memory use and speeds up widget tree comparison. Using const where possible is a core Flutter performance tip.

class Etiket extends StatelessWidget {
  final String metin;
  const Etiket({super.key, required this.metin});

  @override
  Widget build(BuildContext context) {
    return Text(metin);
  }
}

// Usage:
Etiket(metin: 'Selam')     // new object every time
const Etiket(metin: 'Selam') // single object, reused

Canonical instance

Objects produced with const are canonical: all instances made with the same values live at the same memory address. When comparing the widget tree, Flutter can tell whether two const widgets are identical with a single address comparison. This greatly speeds up the diff algorithm.

// non-const widget: each is a new object
Text('a')
Text('a')
// const widget: single object
const Text('a')
const Text('a')

Exercise Print const info

In main, print two lines with print: const tek nesne and canonical hizli.

Show example solution

void main() {
  print('const tek nesne');
  print('canonical hizli');
}

Test yourself

What does a const constructor provide?
- Produces a new object each time
- Produces a single canonical object for same params
- Allows changing parameters at runtime
- Makes the widget invisible
Show answer

Produces a single canonical object for same params — A const constructor merges all instances made with the same params into a single canonical object.

const constructor call

final etiket = ____ Etiket(metin: 'Selam');

Show answer

final etiket = const Etiket(metin: 'Selam');

const constructor concepts

const

Produces a compile-time constant
canonical

Single instance of the same object
performance

Less memory, faster diff
const Etiket(...)

Single object, reused

Next lesson: Summary - StatelessWidget

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