Validating II

In the previous example, we ensured that instances are title-cased. But failure doesn't stop subsequent plug-ins from actually writing to disk.

import pyblish.api

disk = {}
items = ["JOHN.person", "door.prop"]

class CollectInstances(pyblish.api.ContextPlugin):
  order = 0

  def process(self, context):
    for item in items:
      name, suffix = item.split(".")
      context.create_instance(name, family=suffix)

class ValidateNamingConvention(pyblish.api.InstancePlugin):
  order = 1

  def process(self, instance):
    name = instance.data["name"]
    assert name == name.title(), "Sorry, %s should have been %s" % (
      name, name.title())

class ExtractInstances(pyblish.api.InstancePlugin):
  order = 2

  def process(self, instance):
    disk[instance.data["name"]] = instance

pyblish.api.register_plugin(CollectInstances)
pyblish.api.register_plugin(ValidateNamingConvention)
pyblish.api.register_plugin(ExtractInstances)

import pyblish.util
pyblish.util.publish()
print("JOHN" in disk)
# True

To remedy this, we'll turn our attention to some of the pre-defined orders provided by Pyblish.

• Collection

• Validation

• Extraction

• Integration

Collection sets the stage for validation. Once validation is complete, Pyblish takes a moment to consider whether any of the plug-ins that ran threw an error. If it did, it stops processing and returns control to the user.

This behavior is paramount to publishing. If you think back to Quickstart earlies in this guide, you may remember the following visualisation of it.

image

In the next example, we will dig deeper into this mechanism and find out more about what it can do for us.