[Zope-CMF] Implicit and Acquirer

[Dieter Maurer]

George Lee wrote at 2006-3-11 00:41 -0500:
> ...
>What is the difference between Implicit and Acquirer? Between Explicit
>and Acquirer?

An acquirer is an object with two components "aq_self" and "aq_parent".
If asked for an attribute, any acquirer passes the request on
to "aq_self" and returns the result if "aq_self" can deliver
the attribute.

The difference between an ImplicitAcquirer and an ExplicitAcquirer
comes only into play when "aq_self" cannot deliver the asked
for attribute. In this case, an ImplicitAcquirer automatically
passed the request on "aq_parent" while an ExplicitAcquirer fails
(with an AttributeError).

>Including, what methods do Implicit and Explicit *add* or *override*?

Both have the same methods (and attribute).

>For instance, does Explicit add an aq_acquire method?

No. But "aq_acquire" is more important for an "ExplicitAcquirer"
than for an "ImplicitAcquirer":

    "aq_acquire" supports precise control over the lookup
    behaviour of all kinds of acquirers.

    With an "ExplicitAcquirer", you (usually) must use "aq_acquire"
    to look the attribute up in "aq_parent"; an "ImplicitAcquirer"
    would do this automatically (if necessary).

>What else?

Nothing.

>I tried sifting through the C code and the epydoc files but still
>couldn't make sense of it all -- it seems that Implicit and Acquirer
>are really the same, for instance. Answers or references would be very
>appreciated, thanks.

Apparently, you have a reason to use the strange "Implicit and Acquirer"...

In fact, there are two kinds of "Acquirers": "ImplicitAcquirer"
and "ExplicitAcquirer". There is nothing like "Implicit and Acquirer".


-- 
Dieter