Flutter Riverpod - NotifierProvider.family

family를 이용하면 Provider에 매개변수를 추가할 수 있다.

.family를 붙이고, 매개변수 타입을 명시한다.

 

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
 
final counterProvider = NotifierProvider.family<Counter, int, int>(() {
  return Counter();
});
 
class Counter extends FamilyNotifier<int, int> {
  @override
  int build(int initValue) => initValue;
 
  void increment() => state++;
}
 
 
void main() {
  runApp(
    const ProviderScope(
      child: MaterialApp(
        debugShowCheckedModeBanner: false,
        home: MyApp(),
      ),
    ),
  );
}
 
class MyApp extends ConsumerWidget {
  const MyApp({super.key});
 
  @override
  Widget build(BuildContext context, WidgetRef ref) {
    int counter = ref.watch(counterProvider(10));
    return Scaffold(
      body: Center(
        child: Text(
          "$counter",
          style: const TextStyle(
            fontSize: 24,
          ),
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: ref.read(counterProvider(10).notifier).increment,
        child: const Icon(Icons.add),
      ),
    );
  }
}
 

 

counterProvider(10)과 같이 원하는 초기값을 전달할 수 있다.
ref.read(counterProvider(10))에서도 처음 전달한 매개 변수와 동일한 값을 전달해야 한다.