Feature request: expression for string.split(<separator>)

[bergkvist]

Motivation

Underlying problem: The MVT format does not support array properties

I want to send 48 numbers (between 0 and 1) along with every feature. These values represent congestion in electrical grid lines over 48 hours. I want to have a time slider to pick the hour, and style every feature according to their individual congestion at that hour.

A workaround for this that I've used in OpenLayers is to use a string property, which contains all the values separated by semicolon. They are then split up in the style function, and the "current congestion" (according to the slider) is used to style each line individually.

It seems like this is not easily doable in Mapbox GL, which is why I'm making this feature request.

Design Alternatives

It might be the case that there is some good alternative to this approach that I'm not seeing (that does not severely affect performance or scalability).

Design

Proposition: implement the following expression:

["split", separator_string, string]: array

Example:

["split", ";", "1;0.5;0.33;0.101;0.2"]
-> ["1", "0.5", "0.33", "0.101", "0.2"]

The behavior should essentially be the same as the following (javascript):

// ";" is the separator_string:
"1;0.5;0.33;0.101;0.2".split(";")
// ["1", "0.5", "0.33", "0.101", "0.2"]

[andrewharvey]

related to join which I experimented with at https://github.com/mapbox/mapbox-gl-js/compare/join-expression

[mourner]

It seems like this is not easily doable in Mapbox GL, which is why I'm making this feature request.

I believe the current workaround for such use case is to use numbered properties — e.g. "properties": {"value1": 10, "value2": 20, ...}. As an example, this is how it's done in https://electricitytransition.com/

[bergkvist]

I believe the current workaround for such use case is to use numbered properties — e.g. "properties": {"value1": 10, "value2": 20, ...}. As an example, this is how it's done in https://electricitytransition.com/

This is what I ended up doing (and it worked), but a downside of this is that the length/count of the numbered properties is less flexible

(at least in my setup with PostGIS and GeoServer, since "value1", "value2" etc. have to be individual columns in PostGIS)

[MeijiRestored]

Is this being worked on ? i created a tileset with data of European roads for showing a extra e-road shield on these roads in plus of the regular ref=* shield, but sometimes roads have multiple e-road refs (like "int_ref=E 17;E 42", shows litteraly "E17; E 42" on the shield) so a slice() formula could've helped out returning only the first ref when there is multiple...