[Dart/Fluter] Shared Preferences 등 String 값에 임의의 맵을 저장(획득)합니다.

[Dart/Fluter] 모든 Map String

개시하다

부호화

import 'dart:convert';

void main() {
  Map<DateTime, List<dynamic>> _events = {
    DateTime.now(): ['Test', 'List']
  };

  // エンコード汎用関数（Map<DateTime, dynamic>→Map<String, dynamic>）
  Map<String, dynamic> encodeMap(Map<DateTime, dynamic> map) {
    Map<String, dynamic> newMap = {};
    map.forEach((key, value) {
      newMap[key.toString()] = map[key];
    });
    return newMap;
  }

  // json.encodeでMapをStringへ
  String testEncoded = json.encode(encodeMap(_events));

  print(testEncoded.runtimeType);
  print(testEncoded);
}

String
{"2021-04-07 18:09:24.454":["Test","List"]}

디코딩

import 'dart:convert';

void main() {
  Map<DateTime, List<dynamic>> _events = {
    DateTime.now(): ['Test', 'List']
  };

  // エンコード汎用関数（Map<DateTime, dynamic>→Map<String, dynamic>）
  Map<String, dynamic> encodeMap(Map<DateTime, dynamic> map) {
    Map<String, dynamic> newMap = {};
    map.forEach((key, value) {
      newMap[key.toString()] = map[key];
    });
    return newMap;
  }

  // json.encodeでMapをStringへ
  String testEncoded = json.encode(encodeMap(_events));

  // デコード汎用関数（Map<String, dynamic>→Map<DateTime, dynamic>）
  Map<DateTime, dynamic> decodeMap(Map<String, dynamic> map) {
    Map<DateTime, dynamic> newMap = {};
    map.forEach((key, value) {
      newMap[DateTime.parse(key)] = map[key];
    });
    return newMap;
  }

  Map<DateTime, List<dynamic>> newEvents = {};
  // json.decodeでStringをMapへ
  newEvents = Map<DateTime, List<dynamic>>.from(
    // 以下は、実際にはsharedPreferences等を利用し、取得したString値を入れる
    decodeMap(
      json.decode(testEncoded),
    ),
  );

  print(newEvents.runtimeType);
  print(newEvents);
}

JsLinkedHashMap<DateTime, List<dynamic>>
{2021-04-07 18:31:18.014: [Test, List]}