July 1999 - Zope-Dev

RE: [Zope-dev] manage_afterAdd and manage_beforeDelete
by Brian Lloyd 12 Jul '99

12 Jul '99

> >Well, technically there is a constructor of sorts - the DTML method > >or External method that is the target of the "Add" form for your > >ZClass is basically the equivalent of a Python constructor > > I've been adding a method to my ZClasses called > 'manage_afterAdd' (and often, 'manage_beforeDelete'), which > are called by the ZClass framework, I think. It's really > convenient, but I'm not entierly sure they're not reserved > for internal uses. I haven't found anything that uses them yet. > > Mike Pelletier. (I've CC'ed the lists on this, since it probably of interest to other folks out there...) Mike, It probably a bad idea to try to use manage_afterAdd as a handy constructor - the manage_afterAdd and manage_beforeDelete methods are currently a lightweight solution for the fact that there is no "event model" in Zope, but often objects will want to perform some extra activities when they are added/deleted (such as add or remove themselves from Catalogs). The manage_afterAdd, in particular, could get you in trouble, since it will also be called whenever an object cut/copied and pasted to a new location. In that case the construction logic would almost certainly not be appropriate, and could actually run without raising an error, but re-initializing and wiping out the existing data in your object in the process. :( In general, the manage_afterAdd and manage_beforeDelete protocol should be thought of as hooks for fixing up or cleaning up the environment of an object on add/delete/cut/copy/paste events (registering and unregistering with Catalogs, etc.). Brian Lloyd brian(a)digicool.com Software Engineer 540.371.6909 Digital Creations http://www.digicool.com

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RE: Subclassing
by Brian Lloyd 12 Jul '99

12 Jul '99

> Zopists, > > I noticed a post in the list a while back about Subclassing. In order > to make a ZClass inherit from a Base ZClass like lets say a "Findable" > :) base class. Then I have to put all of the ZClasses that I want to > decend from Findable inside the Findable ZClass. Since they > don't show > up in the "Add ZClass" interface. Won't this means that the Findable > ZClass will be very fat indeed? I'm probably misinterpreting the > Subclass issue. > > All my best, > > Jason Spisak A ZClass doesn't need to be contained in another ZClass in order to inherit from it. For example, let's say you create a Product called "SpamCan". Inside of SpamCan, you can create a "Findable" ZClass. After adding that, you can create a "SpamCan" ZClass and "Findable" should show up in the list of possible base classes when you define SpamCan. It should also show up in the bases list if you try to create more ZClasses _inside_ of the SpamCan class. Hope this helps! Brian Lloyd brian(a)digicool.com Software Engineer 540.371.6909 Digital Creations http://www.digicool.com

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RE: [Zope-dev] display a ZClass instance
by Michel Pelletier 12 Jul '99

12 Jul '99

> -----Original Message----- > From: Itamar S.-T. [mailto:itamars@ibm.net] > Sent: Monday, July 12, 1999 1:39 PM > To: zope-dev(a)zope.org > Subject: [Zope-dev] display a ZClass instance > > > I create a ZClass, which inherits from ObjectContainer, with > a index_html > DTML method, and create an instance of the class called test. > > http://localhost:9673/test or > http://localhost:9673/test/index_html works > fine, but if I try doing  from inside the DTML method > http://localhost:9673/test/index_html it writes in the html > file (it doesn't > show up since Netscape thinks its a tag) > > <AnouncementsClass instance at 84f9e10> > > instead of what I want it to do - that is, show the output of > test/index_html. > How then do I display it? Does it need to inherit from anything else? > If I understand your question correctly, try:  Saying  will just render the repr of the object, which because it's a ZClass is excatly what you get. DTML does a bit of sniffing when you #var objects, and if that object is a DTML object (like the test object's index_html) it will render it correctly. -Michel > -- > Itamar - itamars(a)ibm.net > ----------------------------o--------------------------------- -------------o > Sealingwax Greeting Cards | Trust? Ha! The US dollar is > backed by ICBMs! | > http://www.sealingwax.com | --Anonymous Coward, > Slashdot | > > _______________________________________________ > Zope-Dev maillist - Zope-Dev(a)zope.org > http://www.zope.org/mailman/listinfo/zope-dev > > (For non-developer, user-level issues, use the companion list, > zope(a)zope.org, http://www.zope.org/mailman/listinfo/zope ) >

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RE: [Zope-dev] Re: Subclassing
by Alexander Staubo 12 Jul '99

12 Jul '99

Your classes are defined within the same product, right? -- Alexander Staubo http://www.mop.no/~alex/ "He could open a tin of sardines with his teeth, strike a Swan Vestas on his chin, rope steers, drive a steam locomotive and hum all the works of Gilbert and Sullivan without becoming confused or breaking down in tears." --Robert Rankin, _The Book of Ultimate Truths_ >-----Original Message----- >From: zope-dev-admin(a)zope.org [mailto:zope-dev-admin@zope.org]On Behalf >Of Jason Spisak >Sent: 12. juli 1999 21:18 >To: Brian Lloyd >Cc: zope-dev(a)zope.org >Subject: [Zope-dev] Re: Subclassing > > >Brian, > >I just did a cvs update as of 12:00 PM PST and I still don't get any of >the ZClasses which I create in the base class select box. Should I >submit this to the Collector? > >Jason Spisak >webmaster(a)mtear.com > >_______________________________________________ >Zope-Dev maillist - Zope-Dev(a)zope.org >http://www.zope.org/mailman/listinfo/zope-dev > >(For non-developer, user-level issues, use the companion list, >zope(a)zope.org, http://www.zope.org/mailman/listinfo/zope ) >

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RE: [Zope-dev] ZClasses instances become detached from class
by Brian Lloyd 12 Jul '99

12 Jul '99

> This distinction between class and instance is significant. One caveat > concerns folders: Don't make the mistake of creating a folder within > your class. If you do that, each instance will inherit this folder, as > expected. But any modifications to perform on the folder -- including > adding objects -- will show up in all instances. (Of course, > there might > be cases where this is exactly the intended effect.) So in > this case you > should not create the folder within the class, but let one of your > methods create it. > > (Imho, this is a weakness in the current ZClass model: You can't add > constructors. So given the previous paragraph, there's no way you can > say, "When an instance of this class is created, such and such folder > should be created within the instance.") Well, technically there is a constructor of sorts - the DTML method or External method that is the target of the "Add" form for your ZClass is basically the equivalent of a Python constructor, except that it is outside-in, rather than inside-out. Where in Python you might do: def __init__(self, id): self.id=id self.sub=self.CreateNewFolder('blah') ...in the target of your Zope Add form for the ZClass you would do something like this if you were using a DTML Method:        ...or in an external method you might do: def addAMyZClass(self, id, REQUEST=None): """ """ # Get the actual destination object, using the this() # method, to be sure we get it in the right context.. self=self.this() # Create the new instance newob=self.MyZClass(id) newob.id=id # Set properties based on the contents of the Add form newob.propertysheets.Basic.manage_changeProperties(REQUEST) # Add a new Folder to the new instance newob.manage_addFolder('foobar') # Add the new instance to the target object self._setObject(id, newob) return 'OK!' Hope this helps! Brian Lloyd brian(a)digicool.com Software Engineer 540.371.6909 Digital Creations http://www.digicool.com

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RE: [Zope-dev] display a ZClass instance
by Brian Lloyd 12 Jul '99

12 Jul '99

> I create a ZClass, which inherits from ObjectContainer, with > a index_html > DTML method, and create an instance of the class called test. > > http://localhost:9673/test or > http://localhost:9673/test/index_html works > fine, but if I try doing  from inside the DTML method > http://localhost:9673/test/index_html it writes in the html > file (it doesn't > show up since Netscape thinks its a tag) > > <AnouncementsClass instance at 84f9e10> > > instead of what I want it to do - that is, show the output of > test/index_html. > How then do I display it? Does it need to inherit from anything else? Try this:    Brian Lloyd brian(a)digicool.com Software Engineer 540.371.6909 Digital Creations http://www.digicool.com

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display a ZClass instance
by Itamar S.-T. 12 Jul '99

12 Jul '99

I create a ZClass, which inherits from ObjectContainer, with a index_html DTML method, and create an instance of the class called test. http://localhost:9673/test or http://localhost:9673/test/index_html works fine, but if I try doing  from inside the DTML method http://localhost:9673/test/index_html it writes in the html file (it doesn't show up since Netscape thinks its a tag) <AnouncementsClass instance at 84f9e10> instead of what I want it to do - that is, show the output of test/index_html. How then do I display it? Does it need to inherit from anything else? -- Itamar - itamars(a)ibm.net ----------------------------o----------------------------------------------o Sealingwax Greeting Cards | Trust? Ha! The US dollar is backed by ICBMs! | http://www.sealingwax.com | --Anonymous Coward, Slashdot |

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RE: [Zope-dev] ZClasses instances become detached from class
by Michel Pelletier 12 Jul '99

12 Jul '99

> -----Original Message----- > From: Jason Spisak [mailto:webmaster@mtear.com] > Sent: Monday, July 12, 1999 12:19 PM > To: Alexander Staubo > Cc: zope-dev(a)zope.org > Subject: Re: [Zope-dev] ZClasses instances become detached from class > > > Alexander: > > Thanks for the explanation. I now know that I can call it, and it > exists, but you just can't see it. Ahh, the Zen of Zope. Actually it's not too zenish, for the most part you can't 'see' the methods of any object unless they are contained in an ObjectManager (at which point they could probably be considered 'pluggable arms'). The 'Method' view looks alot like a folder container view, but really it's a different thing alltogether. I vote we rename ZClasses 'MrPotatoHeads'. A MrPotatoHead can have pluggable brains, arms, eyes, legs, hair ears and a nose. -Michel > > Jason Spisak > webmaster(a)mtear.com > > > > ZClass methods do not show up inside instances. This is > intentional. Of > > course, you can override methods in an instance by creating > them inside > > a specific instance. But everything defined within the ZClass itself > > belongs to the ZClass. > > > > And that's why, even though you created your index_html, it > doesn't show > > up in the management interface. > > > > (Note, though, that if you're implying that your index_html isn't > > available even when viewing the instance normally, eg., > > http://www.foo.com/myinstance/index_html, then disregard this > > information. I misinterpreted your problem.) > > _______________________________________________ > Zope-Dev maillist - Zope-Dev(a)zope.org > http://www.zope.org/mailman/listinfo/zope-dev > > (For non-developer, user-level issues, use the companion list, > zope(a)zope.org, http://www.zope.org/mailman/listinfo/zope ) >

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RE: [Zope-dev] ZClasses instances become detached from class
by Alexander Staubo 12 Jul '99

12 Jul '99

ZClass methods do not show up inside instances. This is intentional. Of course, you can override methods in an instance by creating them inside a specific instance. But everything defined within the ZClass itself belongs to the ZClass. And that's why, even though you created your index_html, it doesn't show up in the management interface. (Note, though, that if you're implying that your index_html isn't available even when viewing the instance normally, eg., http://www.foo.com/myinstance/index_html, then disregard this information. I misinterpreted your problem.) This distinction between class and instance is significant. One caveat concerns folders: Don't make the mistake of creating a folder within your class. If you do that, each instance will inherit this folder, as expected. But any modifications to perform on the folder -- including adding objects -- will show up in all instances. (Of course, there might be cases where this is exactly the intended effect.) So in this case you should not create the folder within the class, but let one of your methods create it. (Imho, this is a weakness in the current ZClass model: You can't add constructors. So given the previous paragraph, there's no way you can say, "When an instance of this class is created, such and such folder should be created within the instance.") -- Alexander Staubo http://www.mop.no/~alex/ "What the hell, he thought, you're only young once, and threw himself out of the window. That would at least keep the element of surprise on his side." --Douglas Adams, _The Hitchhiker's Guide to the Galaxy_ >-----Original Message----- >From: zope-dev-admin(a)zope.org [mailto:zope-dev-admin@zope.org]On Behalf >Of Jason Spisak >Sent: 9. juli 1999 22:46 >To: zope-dev(a)zope.org >Subject: [Zope-dev] ZClasses instances become detached from class > > >Zopeists, > >I created a new ZClass with no index_html for viewing. The n I made an >instance of it. Then I went back into the ZClass and created an >index_html. Now, to my understanding, and the way it used to work, is >that the index_html will be added for all the instances. However there >is no index_html in the instance. Somewhere the instance go separated >from it's class. Anyone else have that same issue? > > >-- >Jason Spisak >webmaster(a)mtear.com > >_______________________________________________ >Zope-Dev maillist - Zope-Dev(a)zope.org >http://www.zope.org/mailman/listinfo/zope-dev > >(For non-developer, user-level issues, use the companion list, >zope(a)zope.org, http://www.zope.org/mailman/listinfo/zope ) >

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Minor bug in 'Let' tag; fix enclosed
by Phillip J. Eby 11 Jul '99

11 Jul '99

When you use the new 'let' tag with a Python expression containing a syntax error, the Let tag's __init__ method bombs with a NameError, because I didn't sufficiently clean up the code I was cribbing from when I developed it. :) I can't believe it's been in there all this time, but I guess I don't make very many Python syntax errors in my #let tags. :) I also noticed that there were some typos in the 'Let.stx' file, as well a few errors of fact and omission. (E.g., newlines are NOT required between arguments to #let.) Diffs for both files (against current CVS of DocumentTemplate) follow: Index: DT_Let.py =================================================================== RCS file: /cvs-repository/Packages/DocumentTemplate/DT_Let.py,v retrieving revision 1.3 diff -r1.3 DT_Let.py 137c137 < tag) --- > 'let') Index: Let.stx =================================================================== RCS file: /cvs-repository/Packages/DocumentTemplate/Let.stx,v retrieving revision 1.1 diff -r1.1 Let.stx 20,24c20,26 < The #let tag works like the #with tag, but is more flexible in that < it allows you to make multiple assignments, and allows you to chain < assignments, using earlier declarations in later assignments. Notice < inthe ablove example, the 'result' variable is based on 'num' and < 'index', both of which are assigned in the same #let expression. --- > The #let tag works like using a #with tag on a _.namespace() > object, but is more flexible in that it allows you to access > variables without using _[] notation, and also lets you use the > the results of earlier declarations in later assignments. > Notice that in the above example, the 'result' variable is based > on 'num' and 'index', both of which are assigned in the same > #let expression. 26,29c28,30 < Syntacticly, each argument to be evalulated in the head of the let < tag must be seperated by a newline. Enclosing an argument in double < quotes causes it to be evaluated by the DTML expression machinery. < Un-quoted arguments are referenced by name. --- > Enclosing an argument in double quotes causes it to be evaluated by > the DTML expression machinery. Un-quoted arguments are referenced > by name.

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