Question

Suppose I have a content type, Folder, with 4 items.

+ MyObject
 - Child1
 - Child2
 - Child3
 + Child4
  - Child5
 - Child6

Suppose I have another content type (let’s call it Alias). This Alias is mainly a reference to another object but folderish: it can contain a bunch of other aliases. I’m going to use --> to indicate this reference in the following tree representations.(“Reference” is mainly an attribute called “reference” that receives the UID from the target object).

Suppose MyAlias now references my MyObject.

+ MyAlias --> MyObject
 - (Nothing)

When referencing to MyObject, MyAlias doesn’t know that MyObject is a Folder, so the internal MyAlias children don’t exist. I need to loop through everyone, and create, manually, an Alias inside MyAlias, that is a reference (having the same structure) to MyObject children. A little tree showing what should happen:

+ MyAlias --> MyObject
 - Alias --> Child1
 - Alias --> Child2
 - Alias --> Child3
 + Alias --> Child4
  - Alias --> Child5
 - Alias --> Child6

I would like to know the best way to iterate through MyObject items, and create the same structure with another objects, using some kind of loop and using invokeFactory in a subscriber. In the end, I would have BOTH trees existing: one of the actual Folder and children, and another of references to this same Folder and children.

(Summarizing: something like collective.alias, but in a really primitive form, just folders an documents, since I can’t use collective.alias.)

Answer 1

The most elegant and Pythonic solution is to write a recursive generator. Assuming this is a method:

def iter_preorder(self):
    yield self
    # check for folderishness here if a non-folderish
    # node may have children as well
    for x in self.children:
        for y in x.iter_preorder():
            yield y

Then

for x in tree.iter_preorder():
    do_action(x)

This way, you don’t actually have to wrap your action into a function/callable and there’s no inversion of control.