Create safelist-in-flutter-and-dart.dart

Author: vandadnp

tipsandtricks/safelist-in-flutter-and-dart/safelist-in-flutter-and-dart.dart

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+// 🐦 Twitter                   https://twitter.com/vandadnp
+// 🔵 LinkedIn                  https://linkedin.com/in/vandadnp
+// 🎥 YouTube                   https://youtube.com/c/vandadnp
+// 💙 Free Flutter Course       https://linktr.ee/vandadnp
+// 📦 11+ Hours Bloc Course     https://youtu.be/Mn254cnduOY
+// 🔶 7+ Hours MobX Course      https://youtu.be/7Od55PBxYkI
+// 🦄 8+ Hours RxSwift Coursde  https://youtu.be/xBFWMYmm9ro
+// 🤝 Want to support my work?  https://buymeacoffee.com/vandad
+
+import 'dart:collection';
+
+void testIt() {
+  const notFound = 'NOT_FOUND';
+  const defaultString = '';
+
+  final myList = SafeList(
+    defaultValue: defaultString,
+    absentValue: notFound,
+    values: ['Bar', 'Baz'],
+  );
+
+  print(myList[0]); // Bar
+  print(myList[1]); // Baz
+  print(myList[2]); // NOT_FOUND
+
+  myList.length = 4;
+  print(myList[3]); // ''
+
+  myList.length = 0;
+  print(myList.first); // NOT_FOUND
+  print(myList.last); // NOT_FOUND
+}
+
+class SafeList<T> extends ListBase<T> {
+  final List<T> _list;
+  final T defaultValue;
+  final T absentValue;
+
+  SafeList({
+    required this.defaultValue,
+    required this.absentValue,
+    List<T>? values,
+  }) : _list = values ?? [];
+
+  @override
+  T operator [](int index) => index < _list.length ? _list[index] : absentValue;
+
+  @override
+  void operator []=(int index, T value) => _list[index] = value;
+
+  @override
+  int get length => _list.length;
+
+  @override
+  T get first => _list.isNotEmpty ? _list.first : absentValue;
+
+  @override
+  T get last => _list.isNotEmpty ? _list.last : absentValue;
+
+  @override
+  set length(int newValue) {
+    if (newValue < _list.length) {
+      _list.length = newValue;
+    } else {
+      _list.addAll(List.filled(newValue - _list.length, defaultValue));
+    }
+  }
+}