opt.: TimeSeq

lib/data/model/server/time_seq.dart

@@ -0,0 +1,22 @@
+// ignore_for_file: prefer_final_fields
+
+abstract class TimeSeq<T extends TimeSeqIface> {
+  List<T> pre;
+  List<T> now;
+
+  void update(List<T> new_) {
+    pre = now;
+    now = new_;
+
+    if (pre.length != now.length) {
+      pre.removeWhere((e) => now.any((el) => e.same(el)));
+      pre.addAll(now.where((e) => pre.every((el) => !e.same(el))));
+    }
+  }
+
+  TimeSeq(this.pre, this.now);
+}
+
+abstract class TimeSeqIface<T> {
+  bool same(T other);
+}