nc-photos/app/lib/iterable_extension.dart

import 'dart:async';

import 'package:flutter/foundation.dart';
import 'package:np_collection/np_collection.dart';

extension IterableExtension<T> on Iterable<T> {
  Future<List<U>> computeAll<U>(ComputeCallback<T, U> callback) async {
    final list = asList();
    if (list.isEmpty) {
      return [];
    } else {
      return await compute(
          _computeAllImpl<T, U>, _ComputeAllMessage(callback, list));
    }
  }
}

class _ComputeAllMessage<T, U> {
  const _ComputeAllMessage(this.callback, this.data);

  final ComputeCallback<T, U> callback;
  final List<T> data;
}

Future<List<U>> _computeAllImpl<T, U>(_ComputeAllMessage<T, U> message) async {
  final result = await Future.wait(
      message.data.map((e) async => await message.callback(e)));
  return result;
}