flutter - Create Lists from List based on Matching Object Properties

Question

I have a list of objects which contain several properties. I am looking to break the list into several lists composed of objects which posses the same sub-property.

Here is a hypothetical example, say I have a list of Cars. Each Car has properties: id, manufacturerId and color.

I would like to create lists of Cars for those with matching manufacturerId properties.

I have tried using list.where within list.forEach to create new sub-lists, however I get duplicate lists because when the property I am comparing against (A) matches with another property (B), I get another sub-list when:

B = A.

Answer 1

You can use groupBy from package:collection

var carsByManufacturer = groupBy(cars, (car) => car.manufacturerId);

This will create a Map where the keys are the manufacturerID, and the values are lists of cars with that manufacturer.

Then do,

for (final manufacturerEntry in carsByManufacturer) {
      final key = manufacturerEntry.key;
      final value = manufacturerEntry.value;
      final listOfCarsFromSameManufactuer = List.from(entry.value);
      ...
}

You will now have lists called: listOfCarsFromSameManufactuer.