Check for field, add or skip to next step if exists in ModelBuilder?

Question

I am building a model to add many fields to an iteration of feature classes. For each step (broken into sub-models) to add a field I am checking, using a boolean Field Check script, whether the field already 'Exists'. If it does not the output for '0' acts as a precondition to run the Add Field tool. If the field does exists, the sub-model simply ends.

What I need to achieve is a way to have the branch logic end at an output variable regardless of whether the field exists or not, this way I can pass the output to the next 'Add Field' sub-model. Below are pictures of a sub-model and the whole model.

Answer 1

I believe you need only use the Merge Branch model only tool. As you can see in their figure the two branches feed into the merge branch tool resulting in a single output that continues the workflow. Looking at your example I'm not sure you need to use collect values as that returns a list so could never feed into your next sub-model as that takes a FeatureClass as input. The output of your merge branch tool you would expose as a parameter and that is what feeds into your next sub-model.

Personally I think your approach is not the best method. If it were me I would put all the Add Fields into a single sub-model and process them there with a single featureclass feeding in and out of it.

So my sub model would be something like this:

The code in the field Calculate Value tool would be:

import arcpy,os
def hasField(fc):
  arcpy.env.workspace = os.path.dirname(fc)
  fieldList = [field.name for field in arcpy.ListFields(fc)]
  if "Path2" in fieldList: # Path2 is what you change to fit your add field
    b = False
  else:
    b = True
  return b

The tool set up as: