Data Expression

[Hammers211]

Hello! I am attempting to use data expressions as described in this page, however I am getting an error:

I'm trying to use the first example, and have copy/pasted the text and replaced the survey URL and item ID. Can anyone help me figure out what this error means and why I am getting it?

Thank you!

[DougBrowning]

It usually means you are getting a null value in code then trying to access properties of it.  I have found that often the map must have at least 1 feature in it or arcade flips out and you cannot save it.

I think you forgot to post the actual code.  I have been doing a lot of data expressions so post the code and maybe I can see it.

[Hammers211]

// Reference layer using the FeatureSetByPortalItem() function.
var fs = FeatureSetByPortalItem(Portal('https://www.arcgis.com'), '9cf4c3f33ac44231a36030dde78afb9b' , 0, ['list_name'], false);

I'm just doing it bit by bit at the moment, so above is all there is so far. FYI, I actually named it list_name.

[DougBrowning]

I looked up the service id and that is for the form.  You need to use the ID of the Feature Service where the data gets put.  123 always makes both.

[Hammers211]

Where do I find the ID for the Feature Service?

[DougBrowning]

Look in AGOL in the same folder as the form and you will see it.  Open the page then its right at the top in the URL.

[JohannesLindner]

For reference, this is the expression:

// Reference layer using the FeatureSetByPortalItem() function. 
var fs = FeatureSetByPortalItem(Portal('https://www.arcgis.com'), 'd10b9e8dbd7f4cccbd0a938a06c586e9' , 0, ['Report_road_condition'], false);

// Empty dictionary to capture each hazard reported as separate rows. 
var choicesDict = {'fields': [{ 'name': 'split_choices', 'type': 'esriFieldTypeString'}], 
                    'geometryType': '', 'features': []}; 

var index = 0; 

// Split comma separated hazard types and store in dictionary.  
for (var feature in fs) { 
    var split_array  =  Split(feature["Report_road_condition"], ',') 
    var count_arr = Count(split_array) 
    for(var i = 0; i < count_arr; i++ ){ 
        choicesDict.features[index++] = { 
            'attributes': { 'split_choices': Trim(split_array[i]),  
            }} 
}} 

// Convert dictionary to featureSet. 
var fs_dict = FeatureSet(Text(choicesDict)); 

// Return featureset after grouping by hazard types. 
return GroupBy(fs_dict, ['split_choices'], 
       [{ name: 'split_count', expression: 'split_choices', statistic: 'COUNT' }]); 

At a quick glance, I don't see where this error could come from. Anything I can think of would either work or give a different error. Check these points anyway:

• Make sure your portal url and item and sublayer id are correct
• Make sure you query the correct field (Report_road_condition in the example)
• Make sure that this field is a text field

If these don't work, we need to know more to help:

• Test the original expression from the example in your Dashboard, does that work?
• Post your expression
• If possible, share your data publicly

[Hammers211]

Thank you for the suggestions, I will try them ASAP. Where do I find the item/sublayer IDs? Also, by "Make sure that this field is a text field" do you mean that the question type should be text? I need to use select multiple for this particular task. Hopefully I misunderstood.