arcgis-desktopcountmodelbuilder
I'm trying to assign the number of crashes (points) found in a buffer to the line segment found in the same buffer. I need to iterate through the rows of the buffer feature class. I have the model built, all i need to do is figure out how to pass the number of selected crashes (Get count) into the Calculate field in the line feature class.
See the attachment of the model I have built.
I know very little Python. I'm using ArcGIS 10.5 Advanced license.
Without seeing your model it seems odd that your precondition is failing. I knocked a model together (see image below) and it worked fine. When the attribute query created a selection it was copied out when nothing was selected the export was skipped. It makes me wonder if you are using the correct select tool?
When you say empty, I assume you mean "Null" or Empty like this: "".
Pass the ZoneName value into the "Calculate Value" model tool. Then write a basic python function in the "code block" section of the calculate value tool. If values are null:
def getField(field) if field is none: return "Zone A"
then call the function in the "expression" section of the Calculate Value tool like this:
getField("%ZoneName%")
Select String for "Data Type"
Now pass that into value into your field calculation as ("%Value%")
Best Answer
All you need to do is use %Row Count% as the expression in calculate field. Model Builder uses a concept of inline variables which update during the running of the model (through iteration etc. - http://desktop.arcgis.com/en/arcmap/10.3/analyze/modelbuilder/a-quick-tour-of-using-inline-variable-substitution.htm). These are designated through % signs bookending the variable.
Here's somebody asking for essentially the same information on the ESRI community forum a couple of years ago that I dug up (https://community.esri.com/thread/161327). It seems like there's plenty of documentation of inline variables but not many cases of people explicitly advising that this is the nature of the Row Count variable.