topic Re: DateDiff Help in ArcGIS Online Developers Questions

DateDiff Help

MaryEllenStRomain — Fri, 29 Apr 2022 16:10:47 GMT

Hey everyone!

I'm very new to Arcade, so bear with me.

In my AGO map, I have a "Parks" point layer and it's related "Assessments" table. I am trying to calculate a field in the "Parks" layer to display the days since the last assessment, based on the date field in the "Assessments" table.

I understand that I need to use the DateDiff function, but it seems to be having a problem finding the related table and date field I'm wanting to point to.

The relationship is a 1:M, and I'd like to pull the most recent assessment date. I'm not sure if it's the syntax or the 1:M that is causing an error:

var startDate = Date();
var endDate = Date(InspectionDate);
var age = DateDiff(endDate, startDate, 'days');
return age;

Execution Error:Runtime Error: Identifier Not Found. InspectionDate

Any help would be much appreciated! Thanks!

Re: DateDiff Help

jcarlson — Fri, 29 Apr 2022 16:35:32 GMT

To access an attribute, you need to put $feature. in front of the attribute name. You can also use bracket notation, like $feature['InspectionDate'] to pull in an attribute.

Without the $feature., the expression is looking for a variable called "InspectionDate".

Re: DateDiff Help

MaryEllenStRomain — Fri, 29 Apr 2022 16:44:01 GMT

Thanks Josh!

I did play around with that. When I use $feature['InspectionDate'], it returns a Runtime Error: Identifier Not Found. InspectionDate. I'm pulling the 'InspectionDate' from my list of Globals and all of the test data is filled out with dates. Do I need to do something special to indicate that the 'InspectionDate' is in the related table of the $feature?

Thanks for your help!

Re: DateDiff Help

KenBuja — Fri, 29 Apr 2022 16:44:29 GMT

Since you're working with a related table, you have to use FeatureSetByRelationshipName to get the values in that table. Here's an example (and the output):

var test = FeatureSetByRelationshipName($feature,"Source"); for (var f in test) { var output = f.Year; console(output) }

Re: DateDiff Help

jcarlson — Fri, 29 Apr 2022 17:36:50 GMT

Oh jeez, I'm sorry. I went through your post way too quick and just focused on the code portion once I saw that it wasn't accessing a specific feature. More generally, you need to specify a feature to get its attributes, so it's not always $feature, but it needs to be a feature object.

As @KenBuja points out, you need to use another function to access related records.

In text:

Get the related records
Sort by date
Grab the first record
Pull out the date

In code:

// related records var rel = FeatureSetByRelationshipName( $feature, 'Inspections', // the name here will vary, see note below code snippet ['InspectionDate'], false ) // get the latest one as a feature var latest = First( OrderBy( rel, 'InspectionDate DESC' ) ) // return the timestamp of the latest inspection return latest['InspectionDate']

For the relationship name, the expression builder can pipe that in for you, if you don't know it.