I'm working on an A/V Cable and Equipment management project and have run
into an issue. The application is functioning as designed, but I'd like to
add another feature that keeps track of connections between equipment and
cables. Since the app is working as is, I'd like to fit this feature in
the current schema.
Here's a really basic models.py that I wrote to describe the problem.
(This is untested, I wrote this in order to ask the question in detail)
class Connection(models.Model):
name = models.CharField(max_length=50)
gender = models.CharField(max_length=20)
class Manufacturer(models.Model):
name = models.CharField(max_length=200)
# other fields describing the mfg location etc.
class Equipment(models.Model):
"""
components in a rack or a speaker or a microphone; anything
that is connected with cables
"""
name = models.CharField(max_length=100)
manufacturer = models.ForeignKey(Manufacturer)
# other fields describing the equipment type, etc.
class EquipmentConnection(models.Model):
"""
this represents any connection on a piece of equipment
there can be many connections per parentEquipment
"""
parentEquipment = models.ForeignKey(Equipment)
connection = models.ForeignKey(Connection)
labelText = models.CharField(max_length=20)
# other fields here relevant to labels
class Cable(models.Model):
"""
This connects to equipment connections, OR connects to each other for
extending
OR connects to a BreakoutPair
"""
name = models.CharField(max_length=100)
origin_connection = models.ForeignKey(Connection,
related_name="origin_connection")
destination_connection = models.ForeignKey(Connection,
related_name="destination_connection")
class CableBreakout(models.Model):
"""
Some cables have "breakouts" or "tails" that are made up of
multiple channels.
Think of it like the 1/8" iPod cable that breaks out to the Red and
White
RCA connectors.
The two RCA connectors would be the breakout. This comparison is kinda
crappy.
Suffice it to say that this model needs to exist for the next model,
BreakoutPair.
"""
name = models.CharField(max_length=100)
cable = models.ForeignKey(Cable)
whichEndOfTheCable = models.CharField(max_length=20) # just to keep
track of which side of the cable this breakout is on and to prevent
duplicates
class BreakoutPair(models.Model):
"""
there can be many of these related to each Cable Breakout
"""
breakout = models.ForeignKey(CableBreakout)
channel = models.CharField(max_length=20)
labelText = models.CharField(max_length=40)
connection = models.ForeignKey(Connection)
class PatchPoint(models.Model):
"""
here's the question...
I need to keep track of patch points.
A patch point consists of two connections, A and B
It represents the connection point between two items.
For example, plugging in an HDMI cable to a TV would be represented
with this.
The HDMI cable connector is pointA and the HDMI port on the TV is pointB
The problem is that each connection can be any of the following:
- Cable.origin_connection, Cable.destination_connection
- BreakoutPair.connection
- EquipmentConnection.connection
I would like to have this as a database table so that I can check for
errors
such as "This cable connection is already patched into Equipment
Connection X."
and create reports detailing what connections are patched
"""
pointA = ''# ? genericForeignKey? GenericForeignKey would only relate
to a Cable, BreakoutPair, or EquipmentConnection instance\
# not a Cable, BreakoutPair or EquipmentConnection field
pointB = ''# ?
# am I thinking about this wrong? Is there a better way of handling
this?
The problem comes with the PatchPoint model. I can't devise a way to do
this...
Is there a way to structure the database so that this relationship can
work? Would another database type help here, like Redis or something?
Normally, writing out the question leads me to a direction, but I'm stuck
this time.
Thanks for any advice,
-Matt
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