How to call the serialization method from a Generic - dart

Question

Disk Cache with Generics
I am a programmer who comes from JavaScript and PHP, and am developing an App on Flutter, and am having difficulty implementing a cache on the phone's internal storage.
I would like to understand and know if it is possible to create a Generic type class with serialization for JSON so that it can be stored on file.
I've done the Cache implementation in memory and it works fine, plus the implementation of Cache on Disk I'm having difficulty.
Code for Memory cache
class MemCache<T> extends Cache<T> {
Duration cacheValidDuration = Duration(minutes: 30);
DateTime lastFetchTime = DateTime.fromMillisecondsSinceEpoch(0);
RList<T> allRecords = RList<T>();
//is updade cache
bool isShouldRefresh() {
return (null == allRecords ||
allRecords.isEmpty ||
null == lastFetchTime ||
lastFetchTime.isBefore(DateTime.now().subtract(cacheValidDuration)));
}
#override
Future<RList<T>> getAll() {
return Future.value(allRecords);
}
#override
Future<void> putAll(RList<T> objects) {
allRecords.addAll(objects);
lastFetchTime = DateTime.now();
}
#override
Future<void> putAllAsync(Future<RList<T>> objects) async {
allRecords = await objects;
}
}
Code for Disk Cache
How to call the serialization method from a Generic
class DiskCache<T> extends Cache<T> {
Duration cacheValidDuration = Duration(minutes: 30);
DateTime lastFetchTime = DateTime.fromMillisecondsSinceEpoch(0);
RList<T> allRecords = RList<T>();
//is update the cache
bool isShouldRefresh() {
return (null == allRecords ||
allRecords.isEmpty ||
null == lastFetchTime ||
lastFetchTime.isBefore(DateTime.now().subtract(cacheValidDuration)));
}
#override
Future<RList<T>> getAll() async {
await _readFromDisk();
return Future.value(allRecords);
}
#override
Future<void> putAll(RList<T> objects) async {
allRecords.addAll(objects);
lastFetchTime = DateTime.now();
await _writeToDisk();
}
#override
Future<void> putAllAsync(Future<RList<T>> objects) async {
allRecords = await objects;
lastFetchTime = DateTime.now();
await _writeToDisk();
}
//parth
Future<String> get _localPath async {
final directory = await getApplicationDocumentsDirectory();
return directory.path;
}
//file pointer
Future<File> get _localFile async {
final path = await _localPath;
return File('$path/allRecords.json');
}
//write to file
Future<File> _writeToDisk() async {
try {
File recordedFile;
if (allRecords != null) {
var map = allRecords.map((c) {
var item = c as ISerialization;
return item.toJson();
}).toList();
var jsonString = jsonEncode(map);
final file = await _localFile;
// Write the file
recordedFile = await file.writeAsString(jsonString);
}
return recordedFile;
} catch (e) {
print("writeToDisk: " + e.toString());
return null;
}
}
// ************************** issues on this part ******************
Future<RList<T>> _readFromDisk() async {
try {
final file = await _localFile;
// Read the file
String contents = await file.readAsString();
var parsedJson = jsonDecode(contents);
if (allRecords == null) {
allRecords = RList<T>();
}
allRecords.clear();
for (var item in parsedJson) {
// ************************** issues on this part ******************
print(T.fromMap(item));
allRecords.add(T.fromMap(item));
}
return allRecords;
} catch (e) {
print("readFromDisk: " + e.toString());
return null;
}
}
}
Error: The method 'fromMap' isn't defined for the class 'Type'.
- 'Type' is from 'dart:core'.
Try correcting the name to the name of an existing method, or defining a method named 'fromMap'.
allRecords.add(T.fromMap(item));
^^^^^^^