updateValue method
Update the given value
for the given key
in the storage.
The updated value is NOT persistent
Throws an exception if the given value
has not the same Type.
Implementation
void updateValue(String key, dynamic value) {
if (appConfig[key] != null &&
value.runtimeType != appConfig[key].runtimeType) {
throw ("The persistent type of ${appConfig[key].runtimeType} does not match the given type ${value.runtimeType}");
}
appConfig.update(key, (dynamic) => value);
}