Custom Checkin Pipeline
There are four points in the current Application check-in process that the developer can insert handlers to perform custom actions. These events are called checkin/pre_export, checkin/create, checkin/process, checkin/dependency.
Here is a plain pipeline:
<pipeline> <process name="model/> <process name="texture"/> <process name="shader"/> <process name="rig"/> <connect to="texture" from="model" context="model"/> <connect to="shader" from="texture" context="texture"/> <connect to="shot/layout" from="rig" context="rig"/> <connect to="rig" from="texture" context="texture"/> <connect to="shot/lighting" from="shader"/> </pipeline>
If we want to intercept the model process checkin with before exporting occurs and the texture process before and after the export of the node occurs, we will have a pipeline like this:
<pipeline> <process name="model"> <action event="checkin/pre_export" scope="client" class="pyasm.application.common.interpreter.MayaModelCheckinPreexport"/> </process> <process name="texture"> <action event="checkin/pre_export" scope="client" class="pyasm.application.common.interpreter.MayaTextureCheckinPreexport"/> <action event="checkin/process" scope="client" class="pyasm.application.common.interpreter.MayaTextureCheckinProcess"/> </process> <process name="shader"/> <process name="rig"/> <connect to="texture" from="model" context="model"/> <connect to="shader" from="texture" context="texture"/> <connect to="shot/layout" from="rig" context="rig"/> <connect to="rig" from="texture" context="texture"/> <connect to="shot/lighting" from="shader"/> </pipeline>
The class attribute can point to a custom python path, usually accessible on the network where the client computer is on. This python class can do something as simple as adding a cube and parent it to the to-be-exported node, the scene file is free from user-created junk nodes, or making sure a certain special node exists in the scene file. Please to the full override section for some python class examples. The main method required is just execute(). And presumably you will import the application’s python module to do the manipulation desired. For Maya, you would run this to create a cube:
import maya as cmaya cmaya.cmds.polyCube()
This method requires more set-up on the developer’s end as it does not leverage the exisiting application checkin functionalities. This section describes how to customize the checkin pipeline, which is a series of processes, each with an action handler defined.
Normally TACTIC handles many of the details for checking in files. However, this process can be completely taken over and customized.
An example checkin pipeline might look like the following:
<pipeline> <process name="validation"> <action class="pyasm.application.common.interpreter.MayaModelValidate"/> </process> <process name="extractor"> <action class="pyasm.application.common.interpreter.MayaModelCheckin"/> </process> <connect from="validation" to="extractor"/> </pipeline>
This structure is the same for all pipelines defined in TACTIC. It describes a series of processes with actions. The actions have an attribute "class" that handles a particular part of the checkin process. TACTIC delivers a defined pipeline to a pipeline interpreter, which then executes the handlers in order. Handlers make use of the Client API to interact with TACTIC.
For information on the Client API, refer to the Client API Documentation
A process handler is a function or subroutine that contains commands that are executed in response to an event. In TACTIC, all handlers are derived from the Handler class. This class defines a simple interface which has some basic functions which can be overridden:
|execute()||The commands to be performed by the handler.|
The method called when an exception occurs. TACTIC calls the undo() method for each handler in the pipeline in the reverse order that they were executed.
There are several helper methods you can use to set and retrieve information using handlers. Any particular handler has two sources of information:
Package: this data is global to all of the nodes. It is the dictionary data structure that TACTIC delivers to the client machine and includes such settings as status information and user interface selections. This data should be considered read-only.
You can retrieve package information using the method:
where key is the name of the dictionary key for the data. The exact list of the keys delivered will depend on the user interface settings.
Input: this data is received from the previous process handler. The handler itself determines which input it receives.
You can retrieve input information using the method:
Handlers can deliver these values to future nodes with output values, which become the input values for the next node. You can set output information using the method:
The following sample is simple validation handler code that checks a Maya session for the existence of a particular node through its search key.
import maya.cmds as cmds from pyasm.application.common.interpreter import Handler class MayaModelValidate(Handler): def execute(my): # get the search key from the delivered package search_key = my.get_package_value("search_key") # get the sobject from the server sobject = my.server.get_by_search_key(search_key) if not sobject: raise Exception("SObject with search key [%s] does not exist" % \ search_key) # code and verify in maya that the node is in session code = sobject.get('code') if not cmds.ls(code): raise Exception("Cannot checkin: [%s] does not exist" % code) my.set_output_value('sobject', sobject)
This code example, although simple, illustrates a number of handler interaction requirements.
import maya.cmds as cmds
This first line imports the standard Maya command libraries to allow the handler to interact with Maya.
search_key = my.get_package_value("search_key")
This line requires user input from a field in the interface on the search key (unique identifier) for a particular SObject.
sobject = my.server.get_by_search_key(search_key)
Using the search key obtained from the interface, this line uses the
client API to retrieve data about the specific SObject. Handlers can
access the server stub code by using the
my.server prefix. All methods
defined in the Client API are accessible through this type of reference.
(See the Client API documentation for more information.)
The data structure returned is a dictionary of values that can be accessed as follows:
code = sobject.get('code') if not cmds.ls(code): raise Exception("Cannot checkin: [%s] does not exist" % code)
The code then checks the Maya session to verify that a node exists with the same name as defined in the SObject. If not, an exception is created that halts the checkin process and informs the user with the appropriate error message that the checkin failed.