topic Re: Help creating dictionary lookup from variable in ArcGIS Online Questions

Help creating dictionary lookup from variable

LindsayRaabe_FPCWA — Wed, 14 Jun 2023 04:00:05 GMT

I'm trying to write an expression to create custom symbology in a feature service. Currently I've made it this far:

var ftype = $feature.Feature_Type var label = $feature.Label var symbol = Replace(Replace(Replace(Replace(iif(ftype == "Hazard",iif(label == "Asbestos","Asbestos Hazard","Hazard"),ftype), ' ' , '' ), '(' , '' ), ')' , '' ), '-' , '' ) var d = Dictionary('Bore', 1, 'ExternalGate', 2, 'ExternalGateLocked', 3, 'GravelPit', 4, 'Hazard', 5, 'AsbestosHazard', 6, 'Helipad', 7, 'House', 8, 'InternalGate', 9, 'NoAccess', 10, 'OtherInfrastructure', 11, 'PhoneReception', 12, 'Shed', 13, 'WaterPoint', 14, 'WaterPointTank', 15) var category = d.symbol return category

The Replace functions are removing any spaces, brackets and dashes from the value returned from the $feature.Feature_Type value and work fine. The issue I'm having is I can't get the number value out of the dictionary using a variable as an input. I know this must be possible (or it would be pointless having dictionaries) but I can't figure out how to get the d.symbol (line 7) to use the value returned at line 4.

If I change line 7 to say:

var category = d.Bore

...then it all works. As soon as I change d.Bore back to d.symbol then it fails (even though the variable symbol is returning "Bore").

I also tried formatting d.symbol through text concatenation, but that didn't work either.

Re: Help creating dictionary lookup from variable

JohannesLindner — Wed, 14 Jun 2023 06:16:11 GMT

So there are two ways to retrieve (and set) values from a dictionary:

var d = {"A": 1} // Dot notation Console(d.A) // 1 d.B = 2 Console(d.B) // 2 // Bracket notation Console(d["A"]) // 1 d["C"] = 3 Console(d["C"]) // 3

The dot notation is quicker to write and (imo) easier to read, but it does not resolve variables. In your case, it looks for the key "symbol", doesn't find it and raises an error.

To make this work, you need the bracket notation:

var category = d[symbol]

Re: Help creating dictionary lookup from variable

LindsayRaabe_FPCWA — Wed, 14 Jun 2023 07:11:05 GMT

Awesome. Thank you. I'll give that a try tomorrow.

Re: Help creating dictionary lookup from variable

LindsayRaabe_FPCWA — Fri, 16 Jun 2023 00:14:04 GMT

This worked a treat. Thanks. Final code below (changed the way the iif statements worked as well as they weren't returning the expected results - now uses a function to compare labels meaning it can find any Asbestos reference and not just in "Hazard" points).