ZPatterns question
Hi there! Finally I managed to get a basic understanding of how to do things with ZPatterns ;-) So seems quite cool :) (and hopefully I find some time to write some basic howto about it) But I have some little questions: 1. Is it possible to retrieve the set of known IDs from a specialist? Or would I need to add my own method to it which does this (and change it accordingly if I switch to another storage method)? 2. Is it planned to provide something like a virtual folder which acts like a normal object manager but is controlled via ZPatterns (so actually something like Folder with Customizer Support just without the "anchor" in ZODB. (would also require some mechanism asked for in 1.) 3. Is it possible to use ZPatterns also without some exta ZClass defined in a Product? At least if I don't need methods for my objects but simple want to define the attribute they know. Would be nice as I could then hold everything together in one place (the specialist that is) without requiring to install something also in the Products folder of the Control Panel. That's it for now, I will keep experimenting then.. :) cheers, Christian -- Christian Scholz MrTopf@IRC COM.lounge http://comlounge.net/ communication & design cs@comlounge.net
Hi Folks, The Dumb ZPatterns example is updated. Now there is some more realistic object referencing going on, borrowing of code snippets between Specialists and suchlike. There is also more in the way of reasonable documentation, though everything is in flux, and it still doesn't resemble a truly completed product. I just feel the need to get things finished enough that I can stop thinking about them for a while. ;-) In particular there the ToDos now hold references to Doer and Deliverable, and no 'lists' are maintained. One thing I need to do is to have these references automatically 'fixed' when a 'referred to' entity is removed or modified in such a way that the link should be broken.... that's for the next version. If I'm not careful.. it won't be a 'simple' example anymore. There's got to be a line here somewhere (in the sand?). take care, -steve
Hi Christian, Well, nobody else answered that I saw... so I'll take a crack at your questions....
"CS" == Christian Scholz <cs@comlounge.net> writes:
CS> Hi there! CS> Finally I managed to get a basic understanding of how to do CS> things with ZPatterns ;-) So seems quite cool :) (and CS> hopefully I find some time to write some basic howto about it) CS> But I have some little questions: CS> 1. Is it possible to retrieve the set of known IDs from a CS> specialist? Or would I need to add my own method to it which CS> does this (and change it accordingly if I switch to another CS> storage method)? If you store persistently you can use the Rack's method: "defaultRack.getPersistentItemIDs()" but a couple of notes: 1) this returns a BTree object, not a simple list, so you can't iterate through it in DTML. You'll need to copy it to a simple list for that.. and 2) If you change to a different storage you'll need to create your own method (ZSQL Method?). What I've found is that if you have a large number of objects you'll either want to query a Catalog, or an SQL database to get Ids that match some criteria that limit the number of hits to something that makes sense to display in a browser. CS> 2. Is it planned to provide something like a virtual folder CS> which acts like a normal object manager but is controlled via CS> ZPatterns (so actually something like Folder with Customizer CS> Support just without the "anchor" in ZODB. (would also CS> require some mechanism asked for in 1.) Hmmm... I'm not sure what you're after here. Why not just use a Specialist? In what sense do you want it to be virtual? (Are you looking for a dynamic traversal interface that would allow you to map URLs to objects that are managed by ZPatterns? Can you give an example?) CS> 3. Is it possible to use ZPatterns also without some exta CS> ZClass defined in a Product? At least if I don't need methods CS> for my objects but simple want to define the attribute they CS> know. Would be nice as I could then hold everything together CS> in one place (the specialist that is) without requiring to CS> install something also in the Products folder of the Control CS> Panel. I believe you need to either create a Python subclass, or a ZClass subclass of DataSkin. "Raw" DataSkins don't have the right permissions to allow for TTW access. If you're creating a 'product' anyway... just make a 'dummy' class that you can use for storage. CS> That's it for now, I will keep experimenting then.. :) Good Luck! -steve CS> cheers, Christian CS> -- Christian Scholz MrTopf@IRC COM.lounge CS> http://comlounge.net/ communication & design cs@comlounge.net CS> _______________________________________________ Zope-Dev CS> maillist - Zope-Dev@zope.org CS> http://lists.zope.org/mailman/listinfo/zope-dev ** No cross CS> posts or HTML encoding! ** (Related lists - CS> http://lists.zope.org/mailman/listinfo/zope-announce CS> http://lists.zope.org/mailman/listinfo/zope )
Steve Spicklemire wrote:
CS> 2. Is it planned to provide something like a virtual folder CS> which acts like a normal object manager but is controlled via CS> ZPatterns (so actually something like Folder with Customizer CS> Support just without the "anchor" in ZODB. (would also CS> require some mechanism asked for in 1.)
Hmmm... I'm not sure what you're after here. Why not just use a Specialist? In what sense do you want it to be virtual? (Are you looking for a dynamic traversal interface that would allow you to map URLs to objects that are managed by ZPatterns? Can you give an example?)
Reading this just after reading the source to Specialists.py, I had a thought; and tried it out; and it works! :-) You can use SkinScript to define __bobo_traverse__ for a particular kind of DataSkin in a Specialist. For example: WITH SELF COMPUTE __bobo_traverse__=traversal_method Then, define a method in the specialist (or rack) called traversal_method. I used a PythonScript, and gave it the parameter list "REQUEST, name". Make your method return the appropriate object to traverse to from your DataSkin, depending on the name passed. Something like return getattr(container.path.to.somewhere, name) That's the simple version, and it won't give the traversed-to object the correct context most of the time. To do that, I'd need to use an external method, and use the __of__ method to give the returned object an appropriate context. However, it is a start, and proves that it can be done. Take a look in the __bobo_traverse__ method of Specialists.py (from ZPatterns) for a good algorithm for traversal. The variable _marker is almost always a class attribute initialized to [], to make a unique object, as a sentinel. -- Steve Alexander Software Engineer Cat-Box limited http://www.cat-box.net
Steve Alexander wrote:
return getattr(container.path.to.somewhere, name)
That's the simple version, and it won't give the traversed-to object the correct context most of the time. To do that, I'd need to use an external method, and use the __of__ method to give the returned object an appropriate context.
However, if all you are doing is saying "does this object have the named attribute? if not, get it from another specialist", and you're using Specialist.getItem() to do the latter part, then the object you want comes ready-wrapped in the appropriate context, courtesy of the Rack that gives it to you! -- Steve Alexander Software Engineer Cat-Box limited http://www.cat-box.net
Hi Steve! On Thu, Dec 28, 2000 at 10:45:46PM +0000, Steve Alexander wrote:
Steve Spicklemire wrote:
CS> 2. Is it planned to provide something like a virtual folder CS> which acts like a normal object manager but is controlled via CS> ZPatterns (so actually something like Folder with Customizer CS> Support just without the "anchor" in ZODB. (would also CS> require some mechanism asked for in 1.)
Hmmm... I'm not sure what you're after here. Why not just use a Specialist? In what sense do you want it to be virtual? (Are you looking for a dynamic traversal interface that would allow you to map URLs to objects that are managed by ZPatterns? Can you give an example?)
Reading this just after reading the source to Specialists.py, I had a thought; and tried it out; and it works! :-)
You can use SkinScript to define __bobo_traverse__ for a particular kind of DataSkin in a Specialist.
For example:
WITH SELF COMPUTE __bobo_traverse__=traversal_method
that's very cool :) I just created some base class for this from which my ZClasses are derived but nice to know that it's also possible without this base class. (though for this application it's easier with this base class as it's easier to configure then) cheers, Christian
Hi! Actually should answer to these posts... ;-) On Thu, Dec 28, 2000 at 03:11:37PM -0500, Steve Spicklemire wrote:
Hi Christian,
Well, nobody else answered that I saw... so I'll take a crack at your questions....
"CS" == Christian Scholz <cs@comlounge.net> writes:
CS> Hi there!
CS> Finally I managed to get a basic understanding of how to do CS> things with ZPatterns ;-) So seems quite cool :) (and CS> hopefully I find some time to write some basic howto about it)
CS> But I have some little questions:
CS> 1. Is it possible to retrieve the set of known IDs from a CS> specialist? Or would I need to add my own method to it which CS> does this (and change it accordingly if I switch to another CS> storage method)?
If you store persistently you can use the Rack's method:
"defaultRack.getPersistentItemIDs()"
Thanks, also found this out in the meanwhile.
but a couple of notes: 1) this returns a BTree object, not a simple list, so you can't iterate through it in DTML. You'll need to copy it to a simple list for that.. and 2) If you change to a different storage you'll need to create your own method (ZSQL Method?). What I've found is that if you have a large number of objects you'll either want to query a Catalog, or an SQL database to get Ids that match some criteria that limit the number of hits to something that makes sense to display in a browser.
I am now using some method I create inside the specialist for it.
CS> 2. Is it planned to provide something like a virtual folder CS> which acts like a normal object manager but is controlled via CS> ZPatterns (so actually something like Folder with Customizer CS> Support just without the "anchor" in ZODB. (would also CS> require some mechanism asked for in 1.)
Hmmm... I'm not sure what you're after here. Why not just use a Specialist? In what sense do you want it to be virtual?
Well, virtual in the sense as a specialist is no real folder but can provide content from different sources. Thus what I mean is some mechanism which emulates objectIds() etc. so it looks to the user (and the ones using it via dtml) like a normal folder object. Somehow like the Customizer but without the need for actually creating Zope objects. Something inbetween Specialist and Customizer this would be I guess.
(Are you looking for a dynamic traversal interface that would allow you to map URLs to objects that are managed by ZPatterns? Can you give an example?)
yes, something like this comes close I guess. e.g. I have some sql database consisting of people's addresses and I want to create some specialist which queries this database (or how ever this specialist is configured right now in order to get the object ids) and shows it as if it's a normal folder. (seems to me more transparent at some point). But I assume it's not suited for all applications e.g. if the number of objects gets a little bigger. And I guess I can create this myself if I subclass from Specialist and add the rest of the ObjectManager's interface to it.
CS> 3. Is it possible to use ZPatterns also without some exta CS> ZClass defined in a Product? At least if I don't need methods CS> for my objects but simple want to define the attribute they CS> know. Would be nice as I could then hold everything together CS> in one place (the specialist that is) without requiring to CS> install something also in the Products folder of the Control CS> Panel.
I believe you need to either create a Python subclass, or a ZClass subclass of DataSkin. "Raw" DataSkins don't have the right permissions to allow for TTW access. If you're creating a 'product' anyway... just make a 'dummy' class that you can use for storage.
ok, but I still need to define the attributes I want to handle inside a propertysheet of this ZClass, right? Actually what I would like is something which directly resides inside the Specialist and not somewhere outside in some Product folder. So everything is close together in one place.
CS> That's it for now, I will keep experimenting then.. :)
Good Luck!
Oh, it's working better than I thought :) but thanks, christian
Christian Scholz wrote:
Well, virtual in the sense as a specialist is no real folder but can provide content from different sources. Thus what I mean is some mechanism which emulates objectIds() etc. so it looks to the user (and the ones using it via dtml) like a normal folder object. Somehow like the Customizer but without the need for actually creating Zope objects. Something inbetween Specialist and Customizer this would be I guess.
yeah, this is exactly what I'm after too. I'd like the virtual objects the specialist is responsible for to have normal Zope management screens. Also, much mroe trickily, I'd like them to be able to contain each other, although Steve A's __bobo_traverse__ trick might help with this bit... cheers, Chris
Hi!
Well, virtual in the sense as a specialist is no real folder but can provide content from different sources. Thus what I mean is some mechanism which emulates objectIds() etc. so it looks to the user (and the ones using it via dtml) like a normal folder object. Somehow like the Customizer but without the need for actually creating Zope objects. Something inbetween Specialist and Customizer this would be I guess.
yeah, this is exactly what I'm after too. I'd like the virtual objects the specialist is responsible for to have normal Zope management screens.
Well, I think this shouldn't be too difficult to create. Just a subclass of Specialist and add some Contents-Tab, define objectIds() etc. in the Methods tab and call it in the management screen of "Contents". Though the more advanced things like Copy/Paste/Rename might then not be available.. But for me actually it would be sufficient to get the contents.
Also, much mroe trickily, I'd like them to be able to contain each other, although Steve A's __bobo_traverse__ trick might help with this bit...
What do you mean? Nesting Specialists (or these virtual folder specialists)? cheers, Christian -- COM.lounge http://comlounge.net/ communication & design cs@comlounge.net
Christian Scholz wrote:
yeah, this is exactly what I'm after too. I'd like the virtual objects the specialist is responsible for to have normal Zope management screens.
Well, I think this shouldn't be too difficult to create. Just a subclass of Specialist and add some Contents-Tab, define objectIds() etc. in the Methods tab and call it in the management screen of "Contents". Though the more advanced things like Copy/Paste/Rename might then not be available.. But for me actually it would be sufficient to get the contents.
:-S I was hoping for something along the lines of subclass from Specialist and Folder, and override objectIds (+ whatver else?) in my new class to do 'the right thing' I wonder how that would pan out?
Also, much mroe trickily, I'd like them to be able to contain each other, although Steve A's __bobo_traverse__ trick might help with this bit...
What do you mean? Nesting Specialists (or these virtual folder specialists)?
The DataSkins stored in the specialist ;-) cheers, Chris
participants (4)
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Chris Withers -
cs＠comlounge.net -
Steve Alexander -
Steve Spicklemire