pattr Tutorial 1: Patcher Storage
Introduction
Max has a wide variety of objects for storing and managing data. Objects such as table, funbuff, coll, and umenu all store information that you can set manually or via a mechanism within a patch itself. The preset object, which also stores data, is useful for capturing and recalling the ‘states’ of user-interface objects within a patcher, giving you the ability to rapidly restore settings to multiple parts of your patch in one step.
What is pattr?
Often a project in Max will require a more sophisticated state management system than the basic data structures objects allow for. The pattr family of objects (pattr, pattrhub, autopattr, and pattrstorage) provides the functionality of the preset object and adds a more extensive set of state management features:
In this tutorial, we’ll look at some of the basic features of pattr and pattrhub, showing how the objects can be used to communicate remotely with objects anywhere in a Max patch.
Object Binding
Open the tutorial.
Take a look at the tutorial patcher. Turn on the metro object with the toggle object box labeled ‘start’. You should hear some music if you double-click the noteout object and select a valid output synthesizer. The number box attached to the metro object controls the speed of the generated pattern. Click on the colored message boxes to the right of the patch and note that they change the value of that number box even though there are no patch cords or send, forward, or receive objects in the patch.
Clicking in a colored message box changes the metro object’s time value.
The pattr object to the right of the metro object is controlling the value in the number box above it. In the language of patcher storage, we say that our pattr object is bound to the number box. When we send messages to that pattr object, it will at all times refer to the data stored in the number box, allowing us to ask the pattr object what the number is currently set to, as well as tell the pattr object to set the number to a specific value remotely.
Our pattr object has a name - speed - which is set by the object’s argument and allows other pattr-family objects to communicate with it. The pattrhub object at the bottom of the patch can receive messages and forward them to any pattr objects in the patch. By sending the message speed 125 to the pattrhub, we are telling the object to find the pattr with the name speed. If it finds the relevant pattr object, it will instruct the object to send the message 125 to whatever object it is bound to (in this case, our number box).
Unlock the patch and click on the number box attached to the metro object. Select Name… from the Object menu.
Our pattr object is bound to our number box because the bindto attribute of our pattr object is set to the name of our number box (temponum). The act of naming Max objects allows us easier access to them via the pattr system. Note that the pattrhub object controls our number box via the name of the pattr object to which it is bound (speed), not the name of the number box itself (temponum).
Rename the number box to something else and close the Inspector. Try changing settings for the patch by clicking on the message boxes again.
Note that if we rename our referred object, our pattr object can no longer bind to it. In order to rebind it, we need to tell pattr to bind to our number box again.
Open the Inspector for the number box and name it back to temponum. Close the inspector and recreate the pattr object binding to temponum (either delete the object and undo the deletion, or create a new pattr object). Verify that it is receiving updates from the pattrhub object by clicking on the message boxes again.
Instead of recreating the pattr object, we could have sent our newly ‘unbound’ pattr object a bindto message with the name of the number box, setting the bindto attribute to a valid object.
More Ways Than One
Naming a Max object and explicitly binding a pattr to it with its bindto attribute is only one way to get a pattr to refer to an object in our patch. It has the advantage of requiring no connecting patchcords between the two objects, allowing them to communicate from spatially disparate parts of the patcher.
Open the subpatch notes by double-clicking the patcher object containing it. This subpatch contains eight pattr object-bound number box objects that define the four pitches in our pattern generator, as well as the number of beats between each trigger of the pitch. This is the part of the patch that allows us to construct a polyrhythmic pattern off of a single counter object (driven by the metro object in the main patcher).
Click on the message boxes back in the main patcher with this window open and notice that the number box objects in the subpatch update correctly when you click on the different patterns. Clicking on the message box updates the subpatch values, too!
In addition to binding objects to pattr through explicit naming and the bindto attribute, pattr objects can control other Max objects through patchcord connections.
The notes subpatch shows two possible ways to do this:

1. Using the pattr object itself to store the data
2. Automatically binding a pattr object to an object using the pattr object’s middle outlet.
Internal Storage
If a pattr object is unbound, it will store any messages sent in its left inlet and recall them from its left outlet. Messages sent to an unbound pattr object from a pattrhub object will echo out of the left outlet as well.
Unlock the notes subpatch and attach an slider object to the left outlet of one of the pattr objects named val_a, val_b, val_c, or val_d. Recall the pattr objects’ states by clicking on the message boxes in the main patch. Scroll the number box attached to the pattr object. The slider object should move as well.
The pattr objects controlling our pitches are not bound to any single object, and are maintaining the values of the number box objects attached to them not by referring to the objects directly, but by receiving their values as messages. As a result, the number box objects attached to these pattr objects can be deleted and replaced with other objects (or more than one object). Because the pattr object outputs its values when changed (either directly or remotely) we can easily attach multiple objects to the pattr object to set and display values stored in the object.
The use of the prepend object with ‘set’ argument in pattr connections is to prevent the triggering of MIDI events when we recall the pattr object’s state. Unlike most Max objects, pattr objects can be connected to other objects that are directly connected to them in turn without causing a stack overflow.
Automatic Binding
In the same subpatch, try to connect a slider object to the middle outlet of one of the pattr objects labeled mod_a, mod_b, mod_c, or mod_d. The Max window should print an error message and the program should prevent you from making the connection.
The middle outlet of pattr allows for the automatic binding of the pattr to a single object in the same patcher. The number box objects controlling the % objects are communicating with their respective pattr objects just as if we had named them and bound the pattr objects to them manually.
Look at the names for the number box objects by selecting Name… from the Object menu.
The bindto (middle) outlet of pattr objects automatically gives the referring object a name if it doesn’t have one already. The name is based on the class of object attached, and multiple objects of the same class in a patch will be given incrementing notation to uniquely identify them (e.g. number, number[1], number[2], etc.).
Back in the main patch, open the durs subpatch of the main patch by double-clicking the patcher object containing it. Observe that the two pattr objects in there (min and max) have been bound to two number box objects through their middle outlets.
One Hub to Rule Them All
Close the subpatchers and go back to the main tutorial patch. Look at the message boxes again and notice the notation used in them to refer to pattr objects inside subpatchers.
Because most of our pattr objects are inside subpatchers, the pattrhub object refers to them using a colon-separated notation that takes the form

subpatcher:pattr_name
We can communicate to pattr objects in nested subpatchers by the same convention, e.g. a pattr named yikes in a patcher called stuff in a bpatcher called things would be accessed through pattrhub with the name:

things:stuff:yikes
Using the umenu object in the main tutorial patch, select one of the pattr objects in the patch.
In addition to setting the state of pattr objects through pattrhub, we can also query the state of pattr objects, which will then tell pattrhub their internal state or the value of the object to which they’re bound. We do this by sending pattrhub the message get followed by the name of the pattr object we want to query, with no space in the message, e.g. getspeed will poll the state of the pattr named speed.
The number box to the right of the umenu reflects the current value of the selected pattr, output by the second outlet of pattrhub as a message beginning with the name of the queried pattr.
Change the value of the selected pattr by changing the number box next to the umenu. Check to see that the value changed by looking at the number box controlled by that pattr. Select some other pattr objects and change their values, familiarizing yourself with how the system allows you to query and set the states of objects anywhere in the patch.
Conclusion
The pattr objects provide a powerful way to manage data from multiple objects in a Max patch. The pattr object can maintain its own internal information (sent and returned through its leftmost inlet and outlet), or it can bind to a Max user interface object either by naming that object and using the pattr object’s bindto attribute, or by using the middle outlet of the pattr object to automatically name and bind to an object. Each pattr object can only bind to one object at a time. The pattrhub object allows you to control the state of all pattr objects within a patch, including those within subpatchers, which can be accessed through a hierarchical notation system of successive patcher names separated by colons (:) followed by the name of the appropriate pattr object. By sending a get message (followed by the name of a pattr with no intervening space) you can query the state of any pattr object within a patch from a pattrhub.

See Also

Name Description
pattr Patcher-specific, named data wrapper
pattrhub Access all of the pattr objects in a patcher
patcher Create a subpatch within a patch
preset Store and recall the settings of other objects