Joris wrote:
Hello,
I'm trying to implement callback functionality in a static class.
I have a feeling that I'm doing something against the Python philosophy
and not some programming error but any help would be appreciated.
First, a piece of proof-of-concept-code:
*
class Data:
callfunc = None
@staticmethod
def setCallBack(callfunc):
Data.callfunc = callfunc
@staticmethod
def OnData(data):
Data.callfunc(data)
def DataCallback(a):
print 'I received some data: '+ a
Data.setCallBack(DataCallback)
Data.OnData('I have new data')
*
I have defined a class called Data, which I want to use as a "static"
class (i.e. I will never create an instance of it). (I come from a Java
background so forgive me calling this static)
It contains a class variable and 2 static methods.
I also defined a separate function called DataCallback, which would just
print the data it receives.
The goal of this is to use the Data class as a dispatcher of some chunk
of data to whatever function I would like, settable at run-time.
When executing this script, following error occurs:
*Traceback (most recent call last):
File "callback.py", line 17, in <module>
Data.OnData('I have new data')
File "callback.py", line 11, in OnData
Data.callfunc(data)
TypeError: unbound method DataCallback() must be called with Data
instance as first argument (got str instance instead)
*
What I don't understand is why Python is expecting me to call the
DataCallback() function with a Data instance. To my understanding, the
DataCallback() function can be called from a static method and thus does
not require any instance.
Can anyone point me in the right direction ?
DataCallback isn't a static method, it's a plain function. Try this instead:
class Data:
...
@staticmethod
def setCallBack(callfunc):
Data.callfunc = staticmethod(callfunc)
...
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