Extracting a nested attribute from geojson in velocity using Arcade
Hi @NateRogers1- I think there are 2 ways that you could approach this:
- Change the feed configuration slightly. If you're using an HTTP Poller as your feed, you can change from GeoJSON to JSON in the feed configuration. This will expose additional options for you to flatten your objects and also flatten your arrays. If there are certain arrays and objects that you don’t want flattened, you can also add exceptions by clicking on the gear icons. I the below screenshot, I used your sample and changed the Data format to JSON, enabled Flatten, and enabled Flatten arrays.
2. Go the route that you initially suggested an use some Arcade. You could use the Calculate Field tool and set up multiple calculations to parse your field, currentConditions, into separate fields. I'm guessing your field currentConditions is a String field, so you need to first convert it into an array, which then makes parsing a lot easier. Here's some example Arcade:
// my field called 'placeholder' contains the array with nested objects. This field is a Text field
// use fromJSON to convert text into an Array
var currentConditions = fromJSON($feature.placeholder);
// array is stored in var currentConditions. This contains 2 objects
// access first object (at index value 0), then access value associated with field 'conditionId'. This returns 17
var conditionId_1 = currentConditions[0]['conditionId']
// access second object (at index value 1), then access value associated with field 'additionalData'. This returns 'Clear skies. Wind...'
var additionalData_2 = currentConditions[1]['additionalData'];
return additionalData_2;
-Joanna
Hi Nate- I totally understand, Arcade can be a little bit of a learning curve.
I would start with the function reference documentation here. If you're looking to learn more about parsing data returned in an array, maybe first focus on the Array functions area first.
Another quick resource that I like to use is the ArcGIS Arcade Playground. In the screenshot below, you can see how I took the Arcade snippet that I provided, and replaced the currentConditions variable with the text that you initially provided. Then I'm able to execute the Run the expression and change my expression to change the output results.
Some other Velocity-specific resources for Arcade:
Using Arcade in ArcGIS Velocity
Best practices for Arcade expressions in ArcGIS Velocity
-Joanna
