Using field variable to calculate values in ModelBuilder?

Question

I am using ModelBuilder and trying to get a user defined field from a user defined polygon. From this, I want to later populate a different field with calculated values in a model.

Is there a way to get a list of fields from the user defined polygon and use that value to populate the other field?

How would I go about using the user defined field in a VB expression within the calculate value tool?

newfield = [%field%]?

• GISHuman: It might be helpful to post a screenshot of your model here. Have you looked at all into Python?
• nmpeterson: That expression should work, if you have a text parameter called "field". Have you tested it?
• Michael Stimson: Yes, that should work, but why? There is so much danger in doing it this way as you're not picking a field from the feature class you're entering a string - a chance for typo's. Can you explain a bit more about what you're trying to do and hopefully I can come up with something a bit more robust.
• PolyGeo: By a "user-defined polygon" are you meaning a Feature Set? And what do you mean by a "user-defined field"? Perhaps including some screenshots will make your question clearer.

Answer 1

If you want a field picker you have to code it in python.

The code is as follows:

# Import system modules
import arcpy
# Set the parameters
InputFeatureClass = arcpy.GetParameterAsText(0)
InputField = arcpy.GetParameterAsText(1)
arcpy.SetParameter(2, InputField)

And the tool is set as follows:

Input Feature Layer

• Data Type: Feature Layer (You might be using a Feature Set)
• Direction: Input
• Multivalue: No

Inputs Fields

• Data Type: Fields
• Direction: Input
• Multivalue: No
• Obtained from: Input Feature Layer

Output Field

• Data Type: Field
• Direction: Output
• Multivalue: No

It looks like this

Toolbox Script dialog

You should then be able to use this to return a field as a FIELD object, suitable for a input parameter to the Calculate Field tool. A model looks like this: Example Model

I hope that helps.

• CStarbird: What a clever solution. Too bad model builder doesn't inherently support the 'obtained from' option in the parameter settings.\