Access an object to which being bound

[DL Neil]

@AR,


On 28/05/20 8:41 AM, Chris Angelico wrote:
> On Thu, May 28, 2020 at 6:27 AM Abdur-Rahmaan Janhangeer
> <arj.python at gmail.com> wrote:
>>
>> Thanks,
>>
>> Actually i want to keep a reference from B to all A
>> instantiated like in the case of z
>>
>> I have class A and i want to call class B via A
>>
>> You can have
>>
>> def x(self, *args, **kwargs):
>>      return A(*args, **kwargs)
>>
>> but was wondering if we could keep track while
>> doing it via z = ...
>>
> 
> Okay, now I think I get what you're after. Let's simplify and clarify
> things. Let me know if I'm misinterpreting.
> 
> 1) You have a container class that can instantiate objects of a thing class
> 2a) You wish for the container to be aware of all things it has created - OR -
> 2b) You wish for the Thing to be aware of all containers that have created them
> 3) You want this to happen automatically.
> 
> I'm not sure which way round you're trying to do this, so I'll try to
> answer both. Your Container (Hooman) can construct multiple Things
> (Button), and other classes could also construct Things. So you need
> some way to automatically register the Thing as you create it.
> 
> The easiest way to do this would, I think, be to have your Container
> subclass a utility class, and then use self.Button() instead of
> Button(). That can take care of registering the button in some sort of
> list, and then it can still return the button in case you need it for
> something else.
> 
> Would that work? Or am I completely off on my analysis?

Here's some sample code, which may give you some ideas (intriguingly it 
comes from my playing-about with a project @Chris described (some time 
back), which includes the need to 'register' sub-components and to keep 
a count of them):


# PSL
import collections
from itertools import count


class Link():
	'''Contain original link, manipulate for presentation,
		and retain for later action.
	'''

	ID = count( 0 )
	instances = []


	def __init__( self, token:Token, )->None:
		'''Instantiate.'''
		self.token = token

		self.linkNR:int = next( self.ID )	#linkNR
		Link.instances.append( self )		#form a register of instances/links

		self.URL:str = ""

	...more methods here - likely irrelevant to your needs...


class LinksRegister( collections.UserList ):
	'''Links available for use within application.'''

	def __iter__( self ):
		'''Generator.'''
		for link in self.data:
			yield link

	def register_links( self, cls ):
		'''Register all links.'''
		self.data = cls.instances


Once all of the Link() objects have been ascertained, we can make use of 
the class-attributes:

	links_register.register_links( Link )

NB in this scenario it is only necessary to register once - all of the 
links at-once, cf registering each link as it is itself instantiated. 
Also, that each Link() object is not aware that it is/will be 'registered'!


Later, when it is necessary to carry-out the same action on each of the 
objects, we can use the register's iterator/generator (as above).


Critique/other ideas welcome...
-- 
Regards =dn