Make work editor modular

The work editor holds all data for a work and its parts. The widgets for
editing work information are reusable now.

lib/editors/work.dart

@@ -5,81 +5,31 @@ import '../database.dart';
 import '../selectors/instruments.dart';
 import '../selectors/person.dart';
 
-class WorkEditor extends StatefulWidget {
-  final Work work;
-
-  WorkEditor({
-    this.work,
-  });
-
-  @override
-  _WorkEditorState createState() => _WorkEditorState();
-}
-
-class _WorkEditorState extends State<WorkEditor> {
-  final titleController = TextEditingController();
-
-  Backend backend;
+class WorkData {
+  String title = '';
   Person composer;
   List<Instrument> instruments = [];
+  List<WorkData> parts = [];
+}
 
-  @override
-  void initState() {
-    super.initState();
+class WorkProperties extends StatelessWidget {
+  final TextEditingController titleController;
+  final Person composer;
+  final List<Instrument> instruments;
+  final void Function(Person) onComposerChanged;
+  final void Function(List<Instrument>) onInstrumentsChanged;
 
-    if (widget.work != null) {
-      titleController.text = widget.work.title;
-    }
-  }
-
-  @override
-  void didChangeDependencies() {
-    super.didChangeDependencies();
-
-    backend = Backend.of(context);
-
-    if (widget.work != null) {
-      if (widget.work.composer != null) {
-        () async {
-          final person =
-              await backend.db.personById(widget.work.composer).getSingle();
-
-          // We don't want to override a newly selected composer.
-          if (composer != null) {
-            setState(() {
-              composer = person;
+  WorkProperties({
+    @required this.titleController,
+    @required this.composer,
+    @required this.instruments,
+    @required this.onComposerChanged,
+    @required this.onInstrumentsChanged,
   });
-          }
-        }();
-      }
-
-      () async {
-        final selection =
-            await backend.db.instrumentsByWork(widget.work.id).get();
-
-        // We don't want to override already selected instruments.
-        if (instruments.isEmpty) {
-          setState(() {
-            instruments = selection;
-          });
-        }
-      }();
-    }
-  }
 
   @override
   Widget build(BuildContext context) {
-    return Scaffold(
-      appBar: AppBar(
-        title: Text('Work'),
-        actions: <Widget>[
-          FlatButton(
-            child: Text('DONE'),
-            onPressed: () {},
-          ),
-        ],
-      ),
-      body: ListView(
+    return Column(
       children: <Widget>[
         Padding(
           padding: const EdgeInsets.all(16.0),
@@ -104,9 +54,7 @@ class _WorkEditorState extends State<WorkEditor> {
                 ));
 
             if (person != null) {
-                setState(() {
-                  composer = person;
-                });
+              onComposerChanged(person);
             }
           },
         ),
@@ -126,10 +74,103 @@ class _WorkEditorState extends State<WorkEditor> {
                 ));
 
             if (selection != null) {
+              onInstrumentsChanged(selection);
+            }
+          },
+        ),
+      ],
+    );
+  }
+}
+
+class WorkEditor extends StatefulWidget {
+  final Work work;
+
+  WorkEditor({
+    this.work,
+  });
+
+  @override
+  _WorkEditorState createState() => _WorkEditorState();
+}
+
+class _WorkEditorState extends State<WorkEditor> {
+  final titleController = TextEditingController();
+
+  Backend backend;
+  final WorkData data = WorkData();
+
+  @override
+  void initState() {
+    super.initState();
+
+    if (widget.work != null) {
+      titleController.text = widget.work.title;
+    }
+  }
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+
+    backend = Backend.of(context);
+
+    if (widget.work != null) {
+      if (widget.work.composer != null) {
+        () async {
+          final person =
+              await backend.db.personById(widget.work.composer).getSingle();
+
+          // We don't want to override a newly selected composer.
+          if (data.composer != null) {
             setState(() {
-                  instruments = selection;
+              data.composer = person;
             });
           }
+        }();
+      }
+
+      () async {
+        final selection =
+            await backend.db.instrumentsByWork(widget.work.id).get();
+
+        // We don't want to override already selected instruments.
+        if (data.instruments.isEmpty) {
+          setState(() {
+            data.instruments = selection;
+          });
+        }
+      }();
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text('Work'),
+        actions: <Widget>[
+          FlatButton(
+            child: Text('DONE'),
+            onPressed: () {},
+          ),
+        ],
+      ),
+      body: ListView(
+        children: <Widget>[
+          WorkProperties(
+            titleController: titleController,
+            composer: data.composer,
+            instruments: data.instruments,
+            onComposerChanged: (composer) {
+              setState(() {
+                data.composer = composer;
+              });
+            },
+            onInstrumentsChanged: (instruments) {
+              setState(() {
+                data.instruments = instruments;
+              });
             },
           ),
         ],