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newbie tree q - how collapse and expand
by Andy Heath 07 Mar '00

07 Mar '00

I'm getting better but stil learning. I want to collapse/expand a tree at will so that I can come in from particular hyperlinks to a known tree state. I know there are two variables I can set but I don't know how to do this from code. For example how could I have a hyperlink whose HREF is a page containing a tree in such a way that when you get there the tree gets collapsed while another link to the same page doesn't collapse it. Can someone show me some code that dows this please. Andy -- ------------------------------------------------- Andy Heath a.k.heath(a)open.ac.uk The Open University +44 (0) 114 2885738

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Tricky usage of string to integer conversion
by Brian K. Holdsworth 07 Mar '00

07 Mar '00

I am trying to do the following: <dtml-let x:int="REQUEST.get('prod_config')" item="_[REQUEST.get('prod_id')]" price="item.price_list[x]"> <INPUT type="hidden" name="chargetotal" value="<dtml-var price>"> </dtml-let> The prod_config variable is a number (returned as a string) from a SELECT list. The prod_id variable is the id of an object in the same folder as this method that has a price_list attribute. price_list is a list of strings representing prices. This results in a "Name Error" where Zope cannot find "x". If I change line 3 to this: price="item.price_list['x']"> it fixes the Name Error, but then I get a "Sequence Index must be an integer" error on price_list['x']. I would have thought the use of "x:int" in my <dtml-let> would take care of this issue. Seems I can't win! Does anyone know the correct way to do this lookup? Best Regards, Brian Holdsworth

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AUTHENTICATED_USER.getUserName()
by Shaw, Mark 07 Mar '00

07 Mar '00

Hello, Is there a HOW-TO or other documentation that shows how to set up a login page so that you can use AUTHENTICATED_USER.getUserName()? Thanks in advance for any help/pointers provided. -Mark

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Very Newbie Questions
by Tom Scheidt 07 Mar '00

07 Mar '00

This is day 2 with Zope for me: 1. On page 20 of the Zop Content Managers Guide it says "Create a folder under Research with the "id" home and the name "Products Home Page". Im assuming they meant to say "Creat a folder under Products", not Research. 2. If I make a 2 folders within the same folder and one is called images, the other html, the DTML methods calling the images from the html folder wont work because they must be in a subfolder of the images folder. Is there a way to get around this? to have the images and html in seperate folders? 3. In the Zope Content Managers Guide, under the "Creating a Configuration Interface", I am getting an error message when I test the form page called "Home Page Designer". It askes for my username and password then says: Zope Error Zope has encountered an error while publishing this resource. Unauthorized You are not authorized to access manage_changeProperties. ************************* Tom Scheidt www.falsemirror.com tom(a)falsemirror.com *************************

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RE: [Zope] Gaining Enlightenment
by dale w lance 07 Mar '00

07 Mar '00

> -----Original Message----- > From: jiva [mailto:jiva@devware.com] > Sent: Tuesday, March 07, 2000 11:11 AM > To: richard > Cc: jiva; zope > Subject: Re: [Zope] Gaining Enlightenment > > > I don't claim to be an OO master or a ZOPE master, but I'll give this > a shot anyway and share some recent revelations I have had about OO in > general. > > First off, the examples that people always use to demonstrate OO > concepts wind up being more distracting than they are worth. For > instance modeling a can of spam in OO. That would be a logical thing > to do, if you were writing a control program for a can of spam. But Actually the guys at Spam inc. IT do model Spam cans (how about the lot numbers in case of botulism or something?) I believe the reference to Spam was just an example though ;-) > NOT if you were writing a database app! This, I think is one of the > most confusing parts for database programmers coming to OO. > > Second, so if you don't model your can of spam, then what DO you > model? Well, you model *your data* and if your data is a database, > then that's what you model! Soo, you create an object of type > "Products_Table" which contains methods to operate on the entire More likely I would write a Class called "Table" that knows about accessing all relational database tables not just "Products" (see Data Adapters in Zope) > table. Then you create objects of types "Products" which contain > methods to operate on the objects. But since your products can be > many different kinds, you don't "hard code" what kind of product they > are, you just make a generic object that contains generic functions. > If you wind up needing to do something special for a particular > product, *then* you create a subclass of product for that kind of > product that you can use for that. Ie: "Delicate_Product" might be a > subclass of "Product" that might have a special some special methods Would you have a different table for this? This is a debatable topic - if you don't have different attributes for your subclass then, it is argued, you don't really need that subclass. Special methods for this can be done as you propose or just tested for in one class. The reason this is important here (in this discussion) has to do with oo-relational mismatch or impedance. When you are bringing back your objects from the database you are going to have to know which object to "instantiate" (this term is used losely here). This means special handling for your queries. Or you can pay the pain by having two tables which makes your queries for all objects harder. As you can see it isn't necessarily simple. > for dealing with products of that type. Something like "find" should > be a method of the table that returns an instance of your product. > > So, your loop becomes something like this (pseudo code that looks like > c++?): > > while(sData = Input.Read()) > { > MyProduct = new Product(sData); // object init's itself // here you would need to test what kind of Product it is // just before instantiation > if(MyProduct.Validate()) > { > MyProduct.Write(Table); > } > delete MyProduct; > } > > On Tue, Mar 07, 2000 at 09:47:21AM +0000, Richard Moon wrote: > > Dear Zopers, > > > > I read Chris McDonough's How To on Gaining Zope > Enlightenment by Grokking > > Object Orientation. ------------------ Snip! -------------------------------- > > Chris, > > I enjoyed your How-To on Gaining Enlightenment very much. > I've been using > > Zope for a couple of months now and I've made some progress > - my first > > project has been to use it to give access to established > databases over an > > Intranet. Like you I think its wonderful, but like you I > keep getting > > stuck. Never mind, with the help of the mailing lists and > long hours > > reading books on Python etc I've made progress. > > BUT ... (there's always a but isn't there) - no matter how > much I read and > > play around with OO - I still don't 'get it'. My background > is many years > > working with relational databases on Unix - (and there are > thousands like me). > > I just don't get the bit about storing data as objects. > Could we discuss > > this a bit more and perhaps publish my questions and your > answers on > > Zope.org ?? This may help me and the thousands like me. > > OK, you create your class of Spam, which has attributes of > cansize and > > texture and it has methods that display these attributes. > No doubt you > > could add other attributes, such as selling price and > develop a method to > > increase the price by a percentage. OK so far ? Yes this is OK > > Now we create an object (which is an instance of the class > Spam) - which we > > call myfirstcan. We can define the attributes for that > object when we > > create it or later and we can use the methods defined in > the Spam class to > > do so. OK so far ? Yep > > > > What I don't get is how you store and retrieve the objects > you create. There are several ways actually -- Lets use a simple approach, One Class <--> One Table > > Let's go to a more realworld example - how would you > implement a stock > > system using objects ? Let's take the simple table Stock > which has three > > columns > > Product_code Description Price > > and we could enter rows of data into it, for example - > > ABC Spluggifier 20.00 > > CDE Super-spluggifier 25.00 This would translate to a "Stock" object with three attributes as you have stated below - > > > > Now if I was writing a conventional database system I would > maintain the > > above by defining a program which perhaps prompted the user for the > > required columns (Product, Description,Price) and then I > would store the > > users input in a row in a table. Perhaps another program > (the price change > > program) would use a stored procedure to allow price change. OK ? Yes this is still olde kinderhook. > > Now in OO terms I see that I could create a class of Stock > with attributes > > Product, Description and Price. I could create a method to > allow price > > changes. Very neat. For me this method would be an instance method, each instance would have it called upon itself. > > Then I can create an object( i.e a particular stock item) by saying > > something like > > product_1 = Stock(product_code="ABC", > Description="Spluggifier", Price-"20.00") > > Now I can create another object by saying > > product_2 = etc > > but that is not the way you would do it surely. You would > be effectively > > 'hard-coding' each product in your system. > > Surely you would have a program which did something like > > WHILE the user is entering data > > PROMPT user for data > > VALIDATE data > > WRITE data to database > > END WHILE > > How do you do that in OO terms ? Actually you are correct. There will be an input program. You won't see much difference between OO and your conventional database way (if you will allow me to assign that term here). The reason is we haven't actually done anything too significant yet. > > How then do you search and retrieve an object with a > particular value of > > product_code ? Using my assumptions and examples from above I would have the Stock class ask my table class to build a SQL query to do this > > How do you write a program which updates the price of all > stock items where > > the product_code begins with AB by 2%.? As above have the Stock Class have the table class find all "rows" which meet this criteria then for each instance send updatePriceBy(2) where the 2 is an argument and since it is positive the instance of stock will add 2% to its own price > > Thanks for reading this far. Hope you can stop my head spinning ! > > Here comes more spin though I'm afraid (sorry :-P) Up til now I've left out alot of the mechanics. The Table Object knows how to form SQL queries which gets you subsets of your objects (not just rows of data) It in effect provides the code: product_1 = Stock(product_code="ABC",Description="Spluggifier", Price-"20.00") only instead of product_1 it would be 'next_row' or 'this_row' (depending on how you like to think of database cursors). Also somewhere there is a mapping between the Table and the Class it represents. This allows the Table to become a Class, the row to become an instance, and the columns to be attributes. These mappings would be plugged into the above code also (i.e. product_code becomes attributes[1]) This mapping solution is a common pattern - IDL to Corba, DTD to XML in generic terms. Here we start to see OO work. I defined my class and map it to different things such as Corba or XML - now I can ship the object flattened as a string (or some other form) and a reciever can inflate it back. This would be the user input form. This flattening has a special name in ZODB (as far as I can tell) it's "pickling" Hope this doesn't add more head spin. There is much more to this story, we haven't even talked about, such as foreign keys and how to map them to Objects. As far as modeling the data, I don't model a database, just the data, but it also depends on if you are supporting a previously existing database or starting new. I have done both and it is a black art. You have to support management, other departments etc without tipping the boat over, so you generally follow the flow. But for the most part you want to analyze the problem domain from an object point of view from the start. This gives you important insights to other parts of the problem such business processes and object interactions you didn't know about. OO is not just an elaborate ERD (Entity Relationship Diagram) But it is the most common place to start. This is just one way to do it, not necessarily the "Right" way, (if there is such a thing) Hope this Helps Dale

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browser detection
by daniel edmond greenlaw 07 Mar '00

07 Mar '00

is it possible to do browser detection with zope? if so, how? daniel

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empty multiple lists
by Ingo Assenmacher 07 Mar '00

07 Mar '00

Hi everybody, although this may have been discussed several times: I added a multiple property to a class, but when I call the instance's property sheet from the management interface, I get an Type Error, whenever I did not chose anything from the selection box. That is of course ok, because there is no property defined within the instance if I did not select anything. (getProperty(id) fails on None) How do I create an "empty selection"? Thanks for your help BTW: <dtml-call "REQUEST.set('x','[]')"> did not work.

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upload
by Jonathan Park 07 Mar '00

07 Mar '00

Is there a way to upload more than one file or image at once? It seems very cumbersome. thank you! -Jon

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y2kbug - bobobase_modification_time one day back
by Paul Browning 07 Mar '00

07 Mar '00

Martijn Faassen wrote: > People did report this bug elsewhere on the list. Apparently we're waiting > until monday when Jim Fulton can take a look at this. They're pretty sure > it's just a display problem and not something wrong with the object > database, but they want to make sure and check with Jim. Hi. How's Jim getting on with this? Apologies if I missed something on the list. Paul -- The Library, Tyndall Avenue, Univ. of Bristol, Bristol, BS8 1TJ, UK E-mail: paul.browning(a)bris.ac.uk URL: http://www.bris.ac.uk/

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Gaining Enlightenment
by Richard Moon 07 Mar '00

07 Mar '00

Dear Zopers, I read Chris McDonough's How To on Gaining Zope Enlightenment by Grokking Object Orientation. It raised a few questions in my RDBMS-oriented head. So I mailed Chris with these questions but Chris explained he just couldn't answer them right now and asked me to post them to the list. They seem very basic, very fundamental questions to me. So here is my email to Chris - If I get any answers here I would like to include my questions and your answers in a How-To to help those who come after me ! Thanks for any help ! Here's the original email ---------------------------------------------------------------------------- ---------------------------------------------------------- Chris, I enjoyed your How-To on Gaining Enlightenment very much. I've been using Zope for a couple of months now and I've made some progress - my first project has been to use it to give access to established databases over an Intranet. Like you I think its wonderful, but like you I keep getting stuck. Never mind, with the help of the mailing lists and long hours reading books on Python etc I've made progress. BUT ... (there's always a but isn't there) - no matter how much I read and play around with OO - I still don't 'get it'. My background is many years working with relational databases on Unix - (and there are thousands like me). I just don't get the bit about storing data as objects. Could we discuss this a bit more and perhaps publish my questions and your answers on Zope.org ?? This may help me and the thousands like me. OK, you create your class of Spam, which has attributes of cansize and texture and it has methods that display these attributes. No doubt you could add other attributes, such as selling price and develop a method to increase the price by a percentage. OK so far ? Now we create an object (which is an instance of the class Spam) - which we call myfirstcan. We can define the attributes for that object when we create it or later and we can use the methods defined in the Spam class to do so. OK so far ? What I don't get is how you store and retrieve the objects you create. Let's go to a more realworld example - how would you implement a stock system using objects ? Let's take the simple table Stock which has three columns Product_code Description Price and we could enter rows of data into it, for example - ABC Spluggifier 20.00 CDE Super-spluggifier 25.00 Now if I was writing a conventional database system I would maintain the above by defining a program which perhaps prompted the user for the required columns (Product, Description,Price) and then I would store the users input in a row in a table. Perhaps another program (the price change program) would use a stored procedure to allow price change. OK ? Now in OO terms I see that I could create a class of Stock with attributes Product, Description and Price. I could create a method to allow price changes. Very neat. Then I can create an object( i.e a particular stock item) by saying something like product_1 = Stock(product_code="ABC", Description="Spluggifier", Price-"20.00") Now I can create another object by saying product_2 = etc but that is not the way you would do it surely. You would be effectively 'hard-coding' each product in your system. Surely you would have a program which did something like WHILE the user is entering data PROMPT user for data VALIDATE data WRITE data to database END WHILE How do you do that in OO terms ? How then do you search and retrieve an object with a particular value of product_code ? How do you write a program which updates the price of all stock items where the product_code begins with AB by 2%.? Thanks for reading this far. Hope you can stop my head spinning ! Regards Richard Richard Moon richard(a)dcs.co.uk

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