How can you use it with classmethod?

[Bernardrouhi]

This is what i want to do.

from multipledispatch import dispatch

class Sample:
    data = 0

    @dispatch(int, int)
    @classmethod
    def setNum(cls, num1:int, num2:int) -> int:
        cls.data = num1*num2
        return cls.data
    
    @dispatch(int)
    @classmethod
    def setNum(cls, num1:int) -> int:
        cls.data = num1*10
        return cls.data
    
    @dispatch(int, int, str)
    @classmethod
    def setNum(cls, num1:int, num2:int, action:str) -> int:
        if action == "+":
            cls.data = num1+num2
        else:
            cls.data = num1*num2
        return cls.data


print(Sample.setNum(10))
print(Sample.setNum(10,5))
print(Sample.setNum(10,5,"+"))

[javiertxu18]

Hi, I´m using multipledispatch with classmethods. You only have to change the cls.

Try changing this:

    @classmethod
    @dispatch(int, int)
    def setNum(cls, num1:int, num2:int) -> int:
        cls.data = num1*num2
        return cls.data

to this:

    @classmethod
    @dispatch(int, int)
    def setNum(self, num1:int, num2:int) -> int:
        self.data = num1*num2
        return self.data

It worked for me.

Edit ---------------

I just found the documentation where it explains it:

https://pythonhosted.org/multidispatch/#multi-argument-dispatch-for-class-methods

[ferdnyc]

@javiertxu18 That documentation is for multidispatch which isn't the same as multipledispatch. The multipledispatch docs don't cover use in any type of class context. The README says it "supports instance methods", but even that's never discussed in the docs.

Looking at the code, multipledispatch simply does a naïve check whether the first argument of a function is "self", to determine whether something is a method:

multipledispatch/multipledispatch/core.py

Lines 75 to 89 in f91547f

	def ismethod(func):
	"""Is func a method?
	Note that this has to work as the method is defined but before the class is
	defined. At this stage methods look like functions.
	"""
	if hasattr(inspect, "signature"):
	signature = inspect.signature(func)
	return signature.parameters.get("self", None) is not None
	else:
	if sys.version_info.major < 3:
	spec = inspect.getargspec(func)
	else:
	spec = inspect.getfullargspec(func)
	return spec and spec.args and spec.args[0] == "self"