Update GeoJSONSource.clusterProperties to support [["+", ["accumulated"], ["get", "sum"]], ["get", "scalerank"]]

[nflahavan]

New Feature

I would like to be able to use GeoJSONSource.clusterProperties with Operator.accumulated.

Why

In order to express [["+", ["accumulated"], ["get", "sum"]], ["get", "scalerank"]] and other such expressions, the type for the value of the clusterProperties dictionary must support an array of two expressions.

I believe this can be accomplished by adding another Operator called expression with associated value of type Expression. This will require removing String raw type from the enum. Custom encoder/decoder function/init will need to be added as well.

Another possible solution is to change the type of clusterProperties to [String: [Expression.Element]]. This simple solution is less type safe but much easier to implement. It would be nice to make Expression.elements public if this route is taken.

[nflahavan]

@ZiZasaurus is there a way to express [["+", ["accumulated"], ["get", "sum"]], ["get", "scalerank"]] with the current state of the iOS mapbox SDK? I can't seem to figure out a way to do it.

[nflahavan]

re-opened as a bug #1571