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

@@ -5,6 +5,84 @@ import '../database.dart';
 import '../selectors/instruments.dart';
 import '../selectors/person.dart';
 
+class WorkData {
+  String title = '';
+  Person composer;
+  List<Instrument> instruments = [];
+  List<WorkData> parts = [];
+}
+
+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;
+
+  WorkProperties({
+    @required this.titleController,
+    @required this.composer,
+    @required this.instruments,
+    @required this.onComposerChanged,
+    @required this.onInstrumentsChanged,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      children: <Widget>[
+        Padding(
+          padding: const EdgeInsets.all(16.0),
+          child: TextField(
+            controller: titleController,
+            decoration: InputDecoration(
+              labelText: 'Title',
+            ),
+          ),
+        ),
+        ListTile(
+          title: Text('Composer'),
+          subtitle: Text(composer != null
+              ? '${composer.firstName} ${composer.lastName}'
+              : 'Select composer'),
+          onTap: () async {
+            final Person person = await Navigator.push(
+                context,
+                MaterialPageRoute(
+                  builder: (context) => PersonsSelector(),
+                  fullscreenDialog: true,
+                ));
+
+            if (person != null) {
+              onComposerChanged(person);
+            }
+          },
+        ),
+        ListTile(
+          title: Text('Instruments'),
+          subtitle: Text(instruments.isNotEmpty
+              ? instruments.map((i) => i.name).join(', ')
+              : 'Select instruments'),
+          onTap: () async {
+            final List<Instrument> selection = await Navigator.push(
+                context,
+                MaterialPageRoute(
+                  builder: (context) => InstrumentsSelector(
+                    selection: instruments,
+                  ),
+                  fullscreenDialog: true,
+                ));
+
+            if (selection != null) {
+              onInstrumentsChanged(selection);
+            }
+          },
+        ),
+      ],
+    );
+  }
+}
+
 class WorkEditor extends StatefulWidget {
   final Work work;
 
@@ -20,8 +98,7 @@ class _WorkEditorState extends State<WorkEditor> {
   final titleController = TextEditingController();
 
   Backend backend;
-  Person composer;
-  List<Instrument> instruments = [];
+  final WorkData data = WorkData();
 
   @override
   void initState() {
@@ -45,9 +122,9 @@ class _WorkEditorState extends State<WorkEditor> {
               await backend.db.personById(widget.work.composer).getSingle();
 
           // We don't want to override a newly selected composer.
-          if (composer != null) {
+          if (data.composer != null) {
             setState(() {
-              composer = person;
+              data.composer = person;
             });
           }
         }();
@@ -58,9 +135,9 @@ class _WorkEditorState extends State<WorkEditor> {
             await backend.db.instrumentsByWork(widget.work.id).get();
 
         // We don't want to override already selected instruments.
-        if (instruments.isEmpty) {
+        if (data.instruments.isEmpty) {
           setState(() {
-            instruments = selection;
+            data.instruments = selection;
           });
         }
       }();
@@ -81,55 +158,19 @@ class _WorkEditorState extends State<WorkEditor> {
       ),
       body: ListView(
         children: <Widget>[
-          Padding(
-            padding: const EdgeInsets.all(16.0),
-            child: TextField(
-              controller: titleController,
-              decoration: InputDecoration(
-                labelText: 'Title',
-              ),
-            ),
-          ),
-          ListTile(
-            title: Text('Composer'),
-            subtitle: Text(composer != null
-                ? '${composer.firstName} ${composer.lastName}'
-                : 'Select composer'),
-            onTap: () async {
-              final Person person = await Navigator.push(
-                  context,
-                  MaterialPageRoute(
-                    builder: (context) => PersonsSelector(),
-                    fullscreenDialog: true,
-                  ));
-
-              if (person != null) {
-                setState(() {
-                  composer = person;
-                });
-              }
+          WorkProperties(
+            titleController: titleController,
+            composer: data.composer,
+            instruments: data.instruments,
+            onComposerChanged: (composer) {
+              setState(() {
+                data.composer = composer;
+              });
             },
-          ),
-          ListTile(
-            title: Text('Instruments'),
-            subtitle: Text(instruments.isNotEmpty
-                ? instruments.map((i) => i.name).join(', ')
-                : 'Select instruments'),
-            onTap: () async {
-              final List<Instrument> selection = await Navigator.push(
-                  context,
-                  MaterialPageRoute(
-                    builder: (context) => InstrumentsSelector(
-                      selection: instruments,
-                    ),
-                    fullscreenDialog: true,
-                  ));
-
-              if (selection != null) {
-                setState(() {
-                  instruments = selection;
-                });
-              }
+            onInstrumentsChanged: (instruments) {
+              setState(() {
+                data.instruments = instruments;
+              });
             },
           ),
         ],