How to retrieve a Map from a Map in dart efficiently? - flutter

Question

I have a map returned from json.decode of type Map<String,dynamic>
The dynamic part contains another map which I want to have in a separate variable. I managed to do that in the following way:
Map<DateTime, List<DayOffDto>> mapToReturn = Map();
Map<String, dynamic> responseBody = json.decode(
response.body,
reviver: _reviver,
);
if (responseBody == null) {
throw NoDataServerException();
}
responseBody.entries.forEach((element) {
Map map = element.value;
//map.values;
map.entries.forEach((element2) {
mapToReturn[element2.key] = element2.value;
});
});
//mapToReturn contains now the extracted map from responseBody
and the reviver function just does some converting for me
_reviver(dynamic key, dynamic value) {
if (key != null && value is Map && (key as String).contains("-")) {
var object = value;
final DayOffDto dayOffDto = DayOffDto.fromFirebase(
key_firebase: key as String,
parsedJson: value,
rota: rotaParam,
chosenYear: yearParam);
DateTime datetime = Helper.getDateTimeFromDayNumber(
dayOffDto.dayNumber,
dayOffDto.year,
);
Map<DateTime, List<DayOffDto>> internalMap = LinkedHashMap();
internalMap[datetime] = [dayOffDto];
return internalMap;
}
return value;}
I do not think it is the best way of extracting . Any idea for the optimized code?
responseBody.values returns Iterable<V>
so when I do
mapToReturn = responseBody.values i am getting an error

Answer 1

Working with Map can be hard sometimes. I would like to tell you that there is something as easy as mapToReturn = responseBody.values, but as of today, there is not (that I could find).
However, I can give you one small block of code that does the same as your first code block.
As you are not using the keys of your first map, instead of responseBody.entries you should use responseBody.values. So the code block would end up like this:
responseBody.values.forEach((value) {
return value is Map<DateTime, List<DayOffDto>>
? mapToReturn.addAll(value)
: null;
});
And if you are completely sure about the value Type (you should, as you are using a reviver) you can make it only one line of code.
responseBody.values.forEach((value) => mapToReturn.addAll(value));
I hope this can help you!