Can we access/convert the String value from Expression<StringValue>?

[AbdulRehmanNazar]

Thanks for working on mapLibre-compose, which is awesome.
I am using SymbolLayer to show the stops with composables in the iconImage section. in the feature section, I am setting the value of each stop with label like this

     val label = if (index == 0) {
            "S"
        } else if (index == stops.size - 1) {
            "E"
        } else {
            "$index"
        }
            val props: Map<String, JsonElement> =
                mapOf("icon" to JsonPrimitive(label))

in the SymbolLayer, iconImage with switch cases working with feature["icon"].asString() which returns Expression
Is there any extension or way to convert or access to get String from Expression?
Here is SymbolLayer where I added the cases and adding the static hardcoded strings at this moment.

SymbolLayer(
                    id = "stops-source",
                    source = stopGeoJsonSource,
                    iconImage = switch(
                        input = feature["icon"].asString(),
                        case(
                            label = "S",
                            output = image(MapMarkerPainter("S"))
                        ),
                        case(
                            label = "E",
                            output = image(MapMarkerPainter("E")),
                        ),
                        case(
                            label = "1",
                            output = image(MapMarkerPainter("1")),
                        ),
                        case(
                            label = "2",
                            output = image(MapMarkerPainter("2")),
                        ),
                        fallback = image(MapMarkerPainter("A")),
                    ),
                    textColor = const(AppColors.Primary400),
                    textOffset = offset(0.em, 0.6.em),
                )

Thanks in Advance

[sargunv]

You can learn more about style spec expressions here: https://maplibre.org/maplibre-style-spec/expressions/. You can't get the runtime string while building an expression object.

This is likely an XY problem; what are you actually trying to accomplish?

[AbdulRehmanNazar]

@sargunv thanks for your kind reply. Let me explain
Here is the code to generate GeoJsonPoints on Map to show dynamic iconImage using SymbolLayer

fun stopsToGeoJsonPoints(stops: List<Stop>): GeoJsonData {
    val features = stops.mapIndexedNotNull { index, stop ->
        val lat = stop.latitude
        val lon = stop.longitude
        val label = if (index == 0) {
            "S"
        } else if (index == stops.size - 1) {
            "E"
        } else {
            "$index"
        }
        if (lat != null && lon != null) {
            val props: Map<String, JsonElement> =
                mapOf("icon" to JsonPrimitive(label))

            Feature(
                geometry = Point(Position(lon, lat)),
                properties = props
            )

        } else null
    }
    return GeoJsonData.Features(
        FeatureCollection(features)
    )
}

and here is the SymbolLayer with iconImage to load dynamically

SymbolLayer(
                    id = "stops-source",
                    source = stopGeoJsonSource,
                    iconImage = switch(
                        input = feature["icon"].asString(),
                        case(
                            label = "S",
                            output = image(MapMarkerPainter(feature["icon"].toString()))
                        ),
                        case(
                            label = "E",
                            output = image(MapMarkerPainter("E")),
                        ),
                        case(
                            label = "1",
                            output = image(MapMarkerPainter("1")),
                        ),
                        case(
                            label = "2",
                            output = image(MapMarkerPainter("2")),
                        ),
                        fallback = image(MapMarkerPainter("A")),
                    ),
                    textColor = const(AppColors.Primary400),
                    textOffset = offset(0.em, 0.6.em),
)

Where MapMarkerPainter("E") is Composable, which accepts the string and displays on the marker as we can also see from the above screenshot.
Problem is that If there are 50 stops on marker then I have to add 50 cases, I want to access the feature["icon"] value to display on map marker.

My goal is that what I set in properties in icon like S,1,2,3,4...
I want to send it as paramter to composable to display on marker.

Thanks