[Zope] Newbie Questions - many-many relationships? Zope 2 or 3?
Database Question Hello, I'm a newbie, so this is a newbie question! I am currently preparing to build a web application for property lettings, and I'm very interested in what Zope has to offer. The application will need to recognise a number of different objects, such as houses, prospective tenants and property owners (the latter of which I may implement as user types, which would allow these people to log in and amend some of their own information.) I'm very interested in the Object Oriented way of doing things; for example, I'm thinking about implementing houses as a folder-ish object, so it would be able to contain photos of the house in question. The biggest stumbling block I am facing is how to do something Relational in an OO environment. Specifically, I've been scratching my head for a while about how to handle a many-many relationship: a property owner may own more than one house; conversely, a house may have more than one co-owner - consequently it's not appropriate to have either containing the other. I've googled for general information about handling many-many relationships in OO, and most of what I've come across has only indicated that it can be tricky! Having a look through past threads on this mailing list I've noticed a few references to mxmRelations (http://www.zope.org/Members/maxm/products/mxmRelations) which seems to match up - have I got the right end of the stick? Before I jump in with this I'd appreciate any advice or guidance you could provide - it'd be greatly appreciated. While I?m on, I?ve noticed that Zope 3 has been released. Is this now the recommended development environment, or am I better off sticking with Zope 2 for now, and porting my application once Zope 3 is a bit further down the line? I?d greatly appreciate any guidance that can be provided on these subjects. Thanks in advance, Jim ___ Yahoo! Messenger - NEW crystal clear PC to PC calling worldwide with voicemail http://uk.messenger.yahoo.com ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Newbie Questions - many-many relationships? Zope 2 or 3?
Thanks to those who posted suggestions - certainly gave me a few things to think about. Unfortunately I was left with one use Zope 2, one use Zope 3 and a use Plone, but maybe that's just a reflection of the fact that there's more than one Zope way to skin a cat! (yeah, I know I've over-simplified the answers - no offence is meant!) On another thread (http://mail.zope.org/pipermail/zope/2005-June/159738.html), someone said: The problem is that you develop using the ZMI. It's a bad pattern. Don't do it. but the Zope Book (2.7 version)'s chapter on Creating a Basic Application all seems to be through the ZMI. Now, Zope's original appeal to me was using the graphical interface provided by the ZMI to create a collection of objects which if you wire them up correctly will become an application, a view that I think is supported by the Zope Book. However, this view, and what I've read about Zope 3 seems to indicate that this way of doing things is deprecated. Am I correct here? Particularly, if I am building an app that I think I will want to add extra functionality to after it has been installed and is in use, is this a particular reason to avoid developing with ZMI? Say, for example that my Zope App in some way has a House object, which records the address, the owner, and a short description. Later on, I may wish to add further fields to record, say, the number of bedrooms, but the system is already in use - if I've developed in the ZMI, will this make it harder to make an upgrade? Now, if the answer to all of that is yes, then I think that steers me away from the need for TTW development (TTW = Through The Web = ZMI, yes?) which steers me towards Zope 3. I'm interested by the suggestions on how to handle the relations. Hmm, what I would start with is an attribute for a house containing a list of references to owners. And vice versa, each owner has a list of references to houses. I had thought of this, but my concern was about how to make sure that the two records are kept accurate - basically the suggestion is to keep two records saying the same thing, which just triggers alarm bells with me. Another suggestion was: Nah. You either let every PropertyOwner have a list of the ids of HouseProperty objects, or the other way around. Then you index this is the catalog so you can search. Tada! I like the sound of this a bit better - just keep records in one place. So, if I've followed, I let the the house knows who owns it, and if I go to a certain owner's page and want it to give me a list of all the houses she owns, it would do a search through all the house records to see where she's mentioned. Thanks again for all the help so far - lots of food for thought. Thanks, Jim --- Andreas Pakulat [EMAIL PROTECTED] wrote: On 16.Jun 2005 - 23:17:43, Jim Vine wrote: Specifically, I've been scratching my head for a while about how to handle a many-many relationship: a property owner may own more than one house; conversely, a house may have more than one co-owner - consequently it's not appropriate to have either containing the other. I've googled for general information about handling many-many relationships in OO, and most of what I've come across has only indicated that it can be tricky! Hmm, what I would start with is an attribute for a house containing a list of references to owners. And vice versa, each owner has a list of references to houses. Now in Zope references could be implemented via storing the URL of the house and references to Users could be stored via the username (the one the user uses to log in). While Im on, Ive noticed that Zope 3 has been released. Is this now the recommended development environment, or am I better off sticking with Zope 2 for now, and porting my application once Zope 3 is a bit further down the line? Read the archive, short answer is: If you depend only on Zope, you don't want TTW and you want to write a file based product: Zope3 would be possible If you need some existing products or if you need TTW-Code, then you have to stick to Zope2 Andreas -- You're ugly and your mother dresses you funny. ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev ) ___ How much free photo storage do you get? Store your holiday snaps for FREE with Yahoo! Photos http://uk.photos.yahoo.com ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Newbie Questions - many-many relationships? Zope 2 or 3?
On 21.Jun 2005 - 21:59:41, Jim Vine wrote: Say, for example that my Zope App in some way has a House object, which records the address, the owner, and a short description. Later on, I may wish to add further fields to record, say, the number of bedrooms, but the system is already in use - if I've developed in the ZMI, will this make it harder to make an upgrade? Such a change might not be a problem using ZMI, as you can freely add properties to any object. You'd have to supply the data for all existing objects though (but you'd need to do that when using a product too). OK, so there are (at least) three ways of doing things in Zope: 1. Using the ZMI to build an application using standard objects (classes) 2. Creating new classes to use in your app through the ZMI. 3. Creating new classes to use in your app in Python. Most of the Zope Book concentrates on method 1, and the Extending Zope chapter is about method 2 - it mentions method 3, but says that it's beyond the scope of the book. I think I've convinced myself that the complexity of my app takes it beyond method 1, but I'm strugling to get my head around the implications of selecting method 2 or 3. Am I right in thinking that either of these will result in my building a Product? If I want to add extra feature to my product on the development server and then port them to the live server (with all the data on the live server being left in tact), will selection of either of these particularly help or hinder me in this? Apologies for asking so many questions, and thanks to those who have helped so far. I guess I'm just keen to start from the right place at the beginning, so save myself headaches further down the line. Thanks, Jim ___ Yahoo! Messenger - NEW crystal clear PC to PC calling worldwide with voicemail http://uk.messenger.yahoo.com ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Newbie Questions - many-many relationships? Zope 2 or 3?
Hello again, So, following the recommendations from the board I have settled on route 3 - developing a Python Product, using Zope 3. I've been refering a lot to the Zope 3 Book (particularly chapter 13 onwards) and have progressed somewhat. I've created a PropertyFolder class, which can hold Property obects, and following the example in the book I've been able to make it hold *only* Property objects. My Property class is proving a little more difficult, however. When I've tried to make it along the same lines as the message class in the book, I run into difficulties - it seems to be some sort of problem with inheriting from multiple classes / interfaces. My workaround has been that I can include my __setitem__.precondition within the main IProperty interface, and make that subclass from IContainer instead of Interface. This works for me, because I'm not going to want Property objects to contain other Property objects, but I really haven't been able to track down why it should work for the message board, but not for my classes / interfaces. The errors I was getting before my work around seemed to be indicating that it wasn't a container, although I was subclassing BTreeContainer, and implementing three interfaces (one and Interface, one and IContained, and one IContainer). Mostly this presented itself as Zope complaining about using __len__ on the object. (As I say, I have worked around this, and mention it mostly in case it sheds any light on the issue below...) My current problem, however, is proving harder to work around. I want my Property objects to be able to contain Images, and sets of attributes. (A typical set of attributes would describe what is in the kitchen). I have created interfaces IAttribSet(Interface), IAttribSetContainer(IContainer) and IAttribSetKitchen(IAttribSet); and classes AttribSet (implements IAttribSet and IAttribSetContained) and AttribSetKitchen (implements IAttribSetKitchen). I am using IAttribSetContained to create a __parent__ ContainerTypesConstraint. I have wired up the kitchen attrib set in .zcml files. When I 'turn off' implementing IAttribSetContained, my kitchen attrib set is working fine, in that I can add it anywhere, and edit it. However, when I try to add a condition saying where it can go (i.e. I only want it to be within Property objects) it correctly only appears as an Add-menu item within Property objects, but on adding it, I get an error, saying AttribSetKitchen instance has no attribute '__parent__'. My Property and PropertyFolder objects are implemented as BTreeContainers. I'm really quite stumped by this, so I would appreciate any guidance that could be provided on tracking down the source of the errors. Thanks, Jim --- Lennart Regebro [EMAIL PROTECTED] wrote: On 6/22/05, Jim Vine [EMAIL PROTECTED] wrote: I think I've convinced myself that the complexity of my app takes it beyond method 1, but I'm strugling to get my head around the implications of selecting method 2 or 3. Am I right in thinking that either of these will result in my building a Product? Yes. If I want to add extra feature to my product on the development server and then port them to the live server (with all the data on the live server being left in tact), will selection of either of these particularly help or hinder me in this? I don't know, because when I tried 2., it turned out to be quite complicated, and I never understood how to do it. So I did 3. And afterwards I have realized that even if you do understand how to do 2, the fact that you do most of your stuff in the restricted python scripts and dtml or ZPT, means that you have tons of limitations to go around. In addition to that, you can't easily use any proper editors to edit the code, which is very annoying. Method 2 (aka ZClasses) simply seem to offer exactly zero benefits, and loads of drawbacks. Also, as mentioned earlier, unless you want to build your application on top of one of the Zope2 content management systems around (CPS, Plone, Silva, ...) you probably want too use Zope3 for your application development anyway. And then only method 3 (disk based development) is available. -- Lennart Regebro, Nuxeo http://www.nuxeo.com/ CPS Content Management http://www.cps-project.org/ ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev ) ___ How much free photo storage do you get? Store your holiday snaps for FREE with Yahoo! Photos http://uk.photos.yahoo.com ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related
Re: [Zope] Newbie Questions - many-many relationships? Zope 2 or 3?
Hi, I hope it's not considered bad form to answer ones own questions on this board, but I think I've got it sussed. Reading through the ZWiki source from http://svn.zope.org I noticed the following line in the implementations: from zope.app.container.contained import Contained I added this to mine, and it has cleared up the error a treat. Thanks, Jim PS - In scrabling around the net trying to solve this I read somewhere (I think it was a Python Tutorial) the following advice: Use the source (Luke...) I can strongly recommend to any other newbies looking for examples to take a look at to try out ZWiki - it's got a reasonably small number of interfaces and classes, so you can get your head around it, and it covers useful things like containment. --- Jim Vine [EMAIL PROTECTED] wrote: Hello again, So, following the recommendations from the board I have settled on route 3 - developing a Python Product, using Zope 3. I've been refering a lot to the Zope 3 Book (particularly chapter 13 onwards) and have progressed somewhat. I've created a PropertyFolder class, which can hold Property obects, and following the example in the book I've been able to make it hold *only* Property objects. My Property class is proving a little more difficult, however. When I've tried to make it along the same lines as the message class in the book, I run into difficulties - it seems to be some sort of problem with inheriting from multiple classes / interfaces. My workaround has been that I can include my __setitem__.precondition within the main IProperty interface, and make that subclass from IContainer instead of Interface. This works for me, because I'm not going to want Property objects to contain other Property objects, but I really haven't been able to track down why it should work for the message board, but not for my classes / interfaces. The errors I was getting before my work around seemed to be indicating that it wasn't a container, although I was subclassing BTreeContainer, and implementing three interfaces (one and Interface, one and IContained, and one IContainer). Mostly this presented itself as Zope complaining about using __len__ on the object. (As I say, I have worked around this, and mention it mostly in case it sheds any light on the issue below...) My current problem, however, is proving harder to work around. I want my Property objects to be able to contain Images, and sets of attributes. (A typical set of attributes would describe what is in the kitchen). I have created interfaces IAttribSet(Interface), IAttribSetContainer(IContainer) and IAttribSetKitchen(IAttribSet); and classes AttribSet (implements IAttribSet and IAttribSetContained) and AttribSetKitchen (implements IAttribSetKitchen). I am using IAttribSetContained to create a __parent__ ContainerTypesConstraint. I have wired up the kitchen attrib set in .zcml files. When I 'turn off' implementing IAttribSetContained, my kitchen attrib set is working fine, in that I can add it anywhere, and edit it. However, when I try to add a condition saying where it can go (i.e. I only want it to be within Property objects) it correctly only appears as an Add-menu item within Property objects, but on adding it, I get an error, saying AttribSetKitchen instance has no attribute '__parent__'. My Property and PropertyFolder objects are implemented as BTreeContainers. I'm really quite stumped by this, so I would appreciate any guidance that could be provided on tracking down the source of the errors. Thanks, Jim --- Lennart Regebro [EMAIL PROTECTED] wrote: On 6/22/05, Jim Vine [EMAIL PROTECTED] wrote: I think I've convinced myself that the complexity of my app takes it beyond method 1, but I'm strugling to get my head around the implications of selecting method 2 or 3. Am I right in thinking that either of these will result in my building a Product? Yes. If I want to add extra feature to my product on the development server and then port them to the live server (with all the data on the live server being left in tact), will selection of either of these particularly help or hinder me in this? I don't know, because when I tried 2., it turned out to be quite complicated, and I never understood how to do it. So I did 3. And afterwards I have realized that even if you do understand how to do 2, the fact that you do most of your stuff in the restricted python scripts and dtml or ZPT, means that you have tons of limitations to go around. In addition to that, you can't easily use any proper editors to edit the code, which is very annoying. Method 2 (aka ZClasses) simply seem to offer exactly zero benefits, and loads of drawbacks. Also, as mentioned earlier, unless you want to build your application on top of one of the Zope2 content management systems around
Re: [Zope] ZPT with Zope 3 queries - repeat over contained items
Hello, Re-reading this, I realised I'd not provided much information on the repeat problem, so I'm filling in some gaps. This works as I would expect: table border=1 width=80% tr thNumber/th /tr tr tal:repeat=item context/items td tal:content=repeat/item/number#/td /tr /table i.e., if it is repeating over a property folder with four objects in it, it produces a table headed Number and with 4 further rows with numbers 1, 2, 3, and 4 in. However, as soon as I add any meat to it, e.g.: table border=1 width=80% tr thNumber/th thName/th /tr tr tal:repeat=item context/items td tal:content=repeat/item/number#/td td tal:content=item/NameName/td /tr /table I get an error which shows up on the error log as: TypeError: tuple indices must be integers I have tried the second td element as all sorts: td tal:content=item/nameName/td and: td tal:content=item/titleName/td and: td tal:content=item/getIdName/td and: td tal:content=item/streetName/td (all of the objects in the PropertyFolder have a street attribute) These all give the same error. Since my simple test case works, it seems like I'm setting the loop up correctly, but am asking for the data in the wrong way later on. getId and title certainly look from the Zope 2.6 book like they should work, and I tried the rest as guesses. Where should I be looking to find the correct information on how to do this in Zope 3? Thanks, Jim Hello, I'm building an application in Zope 3. I have a container object called a PropertyFolder, which holds Property objects. * Repeating over contained items. I'm trying to create a view which displays a list of all the Property objects in a property folder. I've tried doing this as described in the ZPT chapter of the Zope Book (2.6 edition), using a tal:repeat statement, but I can't seem to get it working. Has something changed in Zope 3? I've tried looking in the Zope 3 book, but none of the references to tal:repeat in there seem to be used for this type of thing. ___ How much free photo storage do you get? Store your holiday snaps for FREE with Yahoo! Photos http://uk.photos.yahoo.com ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Re: ZPT with Zope 3 queries - repeat over contained items
Thanks for that info. I've tried a couple of extra things (below) and if I'm reading the output right I thing you're correct about items returning a tuple, and values returning the object. When I do the repeat like this: tr tal:repeat=item context/items td tal:content=itemName/td /tr The data presented look like this: (u'Property', lettings.property.Property object at 0x027ABEF0) However when I repeat over values instead of items like this: tr tal:repeat=item context/values td tal:content=itemName/td /tr ... they change to this format: security proxied lettings.property.Property instance at 0x027ABEF0 So, it looks to me like values is returning the contained item as single item, rather than a tuple of it... However, I still can't drag anything out of it. Having changed the tal:repeat to item context/values, I have tried item/name, item/Name, item/getName, item/title, item/Title... All return NotFoundError. I've googled, but am yet to find any Zope 3 specific documentation for ZPT - could anyone point me in the direction of some? (Or am I just doing something wrong that wouldn't have worked in Zope 2 either?!?) Thanks, Jim --- Tres Seaver [EMAIL PROTECTED] wrote: -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Jim Vine wrote: Hello, Re-reading this, I realised I'd not provided much information on the repeat problem, so I'm filling in some gaps. This works as I would expect: table border=1 width=80% tr thNumber/th /tr tr tal:repeat=item context/items td tal:content=repeat/item/number#/td /tr /table i.e., if it is repeating over a property folder with four objects in it, it produces a table headed Number and with 4 further rows with numbers 1, 2, 3, and 4 in. However, as soon as I add any meat to it, e.g.: table border=1 width=80% tr thNumber/th thName/th /tr tr tal:repeat=item context/items td tal:content=repeat/item/number#/td td tal:content=item/NameName/td /tr /table I get an error which shows up on the error log as: TypeError: tuple indices must be integers Likely, 'context' is a dict, or a workalike, whose 'items' method returns a sequence of tuples. Therefore, during the tal:repeat, 'item' is a tuple, (key, value). Try using 'values' instead of 'items'. Tres. - -- === Tres Seaver +1 202-558-7113 [EMAIL PROTECTED] Palladion Software Excellence by Design http://palladion.com -BEGIN PGP SIGNATURE- Version: GnuPG v1.2.5 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFCynuh+gerLs4ltQ4RAl5uAKCRzRzV+g1M8gcbV07jSNfCQbWbhgCg0nL4 2POVN4oUQepYUIQ+pR1IPRU= =fBFx -END PGP SIGNATURE- ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev ) ___ How much free photo storage do you get? Store your holiday snaps for FREE with Yahoo! Photos http://uk.photos.yahoo.com ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
