On 02/21/2015 07:15 AM, pfranke...@gmail.com wrote:
Hello!
I have a best-practice question: Imagine I have several hardware devices that I
work with on the same I2C bus and I am using the python smbus module for that
purpose. The individual devices are sensors, ADC, DAC components. As I said, I
would like to derive the corresponding classes from one common class, let's say
I2CDevice, so that they can share the same bus connection (I don't want to do a
import smbus, ..., self.bus = smbus.SMBus(1) all the time). Of course, I could
just pass the the bus reference to each instance, but I am pretty sure that
there must be a nicer way to do this.
In particular, I imagine the following: It should be possible that I have two
classes, ADC_I2C, DAC_I2C which share the same base class. Once I create an
instance of ADC_I2C or DAC_I2C it should check whether a bus object exists, if
not, it should create one and the other class should be able to use this bus
reference as well. Do you get my point? I am pretty sure that such a design
pattern should exist, maybe also in the reference of DB connections?
Unfortunately I did not find something like this.
I think you should write the code (or at least a skeleton version). I
suspect the answer will become obvious to you, once you're not worrying
about design patterns, or being java compatible.
Regardless of whether you inherit from a common base class, both classes
can have an attribute with a "bus object" in it. The question becomes
who initializes it, and who decides to reuse the "same one". Your
wording doesn't make that the least bit clear to me; maybe your sample
code will.
Many times when you'd have a common base class in Java or C++, you just
have to have a common member or two in Python.
On the other hand, once you start implementing, maybe it'll become
obvious that there's enough shared code for a common base class.
The first question is whether an ADC "is-a" bus, or "has-a" bus. Stated
that way it sounds like you should have an attribute in ADC which is a
bus object.
Any hints are highly appreciated!
Thanks!
--
DaveA
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