LabelDefinition with int parameter

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02-08-2019 03:07 AM
GonzaloMuöoz
Occasional Contributor

I have following StringBuilder:
{
"allowOverlapOfLabel": "allow" ,
"allowOverlapOfFeatureBoundary": "allow" ,
"allowOverlapOfFeatureInterior": "allow" ,
"labelExpressionInfo": {
"expression": "return $feature.Name;"},
"labelPlacement": "esriServerPointLabelPlacementCenterRight",
"multiPart": "labelPerFeature",
"minScale": "return $feature.MinScale;",
"maxScale": 0,
"symbol": {
"color": [255,255,255,255],
"haloColor": [51,51,51,255],
"haloSize": 1.5,
"font": {"size": 10, "weight": "bold"},
"type": "esriTS"}
}

My problem is that when doing LabelDefinition.FromJson method with this string, I get an invalid character exception on minScale value. 

MinScale attribute is a string defined in the attributes of each graphic and minScale key on the Json needs an integer. How can this conversion be done or how can I pass minScale value as a $feature value?

Thanks

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MichaelBranscomb
Esri Frequent Contributor

Hi,

Only properties that are explicitly described as expressions, such as the `labelExpressionInfo.expression` or the `labelAngleInfo.angleExpressionInfo.expression` can (and must) contain an Arcade expression.

Cheers

Mike

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7 Replies
ThadTilton
Esri Contributor

Hey Gonzalo - 

You might want to take a look at the approach (and code) described in this blog: https://community.esri.com/community/developers/native-app-developers/arcgis-runtime-sdk-for-net/blo....

In addition to making the code easier to work with and maintain, you have some control over how the values you're using are returned (int vs string, etc.). 

Thad

UPDATE:

Sorry, after taking a closer look I see that the problem you're facing is getting the expression "return $Feature.MinScale" to provide an integer from the underlying string value.

I'm not sure, but it looks like the Arcade "Number" function might do the trick: Data Functions | ArcGIS for Developers 

GonzaloMuöoz
Occasional Contributor

Hi Thad,

thanks for the answer. I'm trying your recommendation using Number expresion like this just to test how it works and if I can use it. This is how I'm using it::
labelBuilder.AppendLine("\"minScale\": Number('700000','######'),");

and I'm getting following exception:

"expecting NaN": Num : 303

What's the problem now?

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ThadTilton
Esri Contributor

I tested this a little on my end and I'm experiencing the same thing. 

There's a nice tool here for testing Arcade expressions: ArcGIS Arcade | ArcGIS for Developers and the `Number` expressions I tried were returning valid values. When I tried it in my labeling JSON, however, I got mixed results.

If I tried it in the labeling expression it worked. For example:

"\"expression\": \" Number('1000000', '########') + ' meters';\"},"

But the same expression fails when used for `minScale`:

"\"minScale\": Number('1000000', '########'),"

I'm not sure if the expression is supposed to work outside of the actual label expression. I'll look into that further and let you know what I find.

Thad

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ThadTilton
Esri Contributor

Arcade expressions are indeed only supported for use in label or rotation expressions. Other label properties (like minimum scale) cannot interpret Arcade. As ArcGIS Pro enables more labeling properties to use expressions, ArcGIS Runtime will add support as well.

GonzaloMuöoz
Occasional Contributor

Do you know when this functionality will be added?

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GonzaloMuöoz
Occasional Contributor

Any advance on this?

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MichaelBranscomb
Esri Frequent Contributor

Hi,

Only properties that are explicitly described as expressions, such as the `labelExpressionInfo.expression` or the `labelAngleInfo.angleExpressionInfo.expression` can (and must) contain an Arcade expression.

Cheers

Mike

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