回答編集履歴
2
クラスで扱う例を追記
answer
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@@ -15,4 +15,121 @@
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);
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}
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}
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```
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また、根本的な問題になりますが、このようなネストしたデータは、クラスに変換して扱った方が良いです。
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どんなアプリを作っているか分からないので大体の雰囲気だけ示すと、以下のような感じです。
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```dart
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// ユーザーを表すクラス
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class User {
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final String key;
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final String name;
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final Sex sex;
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final List<WeightData> weightHistory;
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User({
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this.key,
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this.name,
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this.sex,
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this.weightHistory,
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});
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}
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// 体重データを表すクラス
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class WeightData {
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final double value;
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final DateTime date;
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WeightData({
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this.value,
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this.date,
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});
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}
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// 性別を表すEnum
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enum Sex {
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Male,
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Female,
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Unknown,
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}
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// これらを使うと、データはこんな感じで表現できる
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final List<User> allData = [
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User(
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key: '1',
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name: 'Jim',
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sex: Sex.Male,
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weightHistory: [
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WeightData(
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date: DateTime(2020, 8, 25),
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value: 5.1,
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),
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WeightData(
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date: DateTime(2020, 8, 26),
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value: 5.4,
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),
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],
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),
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User(
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key: '2',
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name: 'Tom',
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sex: Sex.Male,
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weightHistory: [
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WeightData(
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date: DateTime(2020, 8, 25),
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value: 5.1,
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),
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WeightData(
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date: DateTime(2020, 8, 26),
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value: 5.4,
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),
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],
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),
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];
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// 実際の使用例
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class ExamplePage extends StatefulWidget {
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final String name;
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const ExamplePage({
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Key key,
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@required this.name,
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}) : super(key: key);
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@override
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_ExamplePageState createState() => _ExamplePageState();
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}
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class _ExamplePageState extends State<ExamplePage> {
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List<DataPoint<DateTime>> data;
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@override
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void initState() {
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super.initState();
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this.data = allData
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.where((user) => user.name == widget.name)
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.map((user) => user.weightHistory)
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.expand((data) => data)
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.map(
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(data) => DataPoint<DateTime>(
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value: data.value,
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xAxis: data.date,
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),
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)
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.toList();
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}
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@override
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Widget build(BuildContext context) {
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return Scaffold(
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body: Center(
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child: Text('${data[0]}'),
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),
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);
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}
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}
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18
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```
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1
コード修正
answer
CHANGED
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@@ -1,9 +1,11 @@
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1
1
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`Map`型からvalueの部分だけを取り出すには、`values`という便利なプロパティが使えます。
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2
2
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3
3
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```dart
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4
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-
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for (int i = 0; i < allData.length; i++) {
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5
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-
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final info = allData[i]['data'] as Map<String, dynamic>;
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if (info['name'] != widget.name) continue;
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final weightData = info['weight'] as Map<String, Map>;
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for (var value in weightData.values) {
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data.add(
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DataPoint<DateTime>(
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@@ -12,4 +14,5 @@
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),
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15
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);
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14
16
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}
|
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17
|
+
}
|
|
15
18
|
```
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