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• Model objects versions in Django

  - by pablo

  Hi I'm building an e-commerce website. I have a Product and Order models. It's possible that a customer order a product and then the admin change its price or other fields before the customer actually get it. A possible solution is to add a 'version' field to the Product model. When the admin update a product field I'll add a timestamp and create a new object instead of updating the old one. An Order will have a reference to a specific product version. Does this make sense? Will overriding the Product Save method be sufficient to make it work? Thanks

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• BasedOn property not working with ListView

  - by bobjink

  When I use the following code it works because I am using a ListBox <UserControl.Resources> <Style BasedOn="{StaticResource {x:Type ListBox}}" TargetType="{x:Type ListBox}"> <Setter Property="HorizontalContentAlignment" Value="Stretch"/> <Setter Property="Background" Value="Transparent" /> </Style> </UserControl.Resources> But when I use the following code to a ListView I get an warning/exception <UserControl.Resources> <Style BasedOn="{StaticResource {x:Type ListView}}" TargetType="{x:Type ListView}"> <Setter Property="HorizontalContentAlignment" Value="Stretch"/> <Setter Property="Background" Value="Transparent" /> </Style> </UserControl.Resources> "StaticResource reference 'System.Windows.Controls.ListView' was not found." Why and how to solve it? I want the functionality of a ListView.

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• Decimal data Type Display scale part as zero

  - by Wael Dalloul

  I have Decimal field in SQLserver 2005 table, Price decimal(18, 4) if I write 12 it will be converted to 12.0000, if I write 12.33 it will be converted into 12.3300. Always it's putting zero to the right of the decimal point in the count of Scale Part(4). I was using these in SQL Server 2000, it was not behaving like this, in SQL Server 2000 if I put 12.5 it will be stored as 12.5 not as 12.5000 what SQLServer2005 do. My Question is how to stop SQL Server 2005 from putting zeros to the right of the decimal point?

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• [PHP] building html tables from query data... faster?

  - by Andrew Heath

  With my limited experience/knowledge I am using the following structure to generate HTML tables on the fly from MySQL queries: $c = 0; $t = count($results); $table = '<table>'; while ($c < $t) { $table .= "<tr><td>$results[0]</td><td>$results[1]</td> (etc etc) </tr>"; ++$c; } $table .= '</table>'; this works, obviously. But for tables with 300+ rows there is a noticeable delay in pageload while the script builds the table. Currently the maximum results list is only about 1,100 rows, and the wait isn't long, but there's clearly a wait. Are there other methods for outputting an HTML table that are faster than my WHILE loop? (PHP only please...)

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• F# Interactive bug?

  - by John Reynolds

  I've tried the following code in VS2010: open System.Security.Cryptography let rsaTest1 = let ecKey = [|0uy..143uy|] // junk data for testing let ecKeyMod = ecKey.[8..8+128-1] let ecKeyExp = ecKey.[136..136+8-1] let rsa = RSAParameters(Modulus = ecKeyMod, Exponent = ecKeyExp) rsa let rsaTest2 = let ecKey = [|0uy..143uy|] // junk data for testing let rsa = RSAParameters(Modulus = ecKey.[8..8+128-1], Exponent = ecKey.[136..136+8-1]) rsa If I highlight all code and send it to F# Interactive (Alt+Enter), then rsaTest1 works, but rsaTest2 gives an error message, System.NullReferenceException: Object reference not set to an instance of an object. at <StartupCode$FSI_0004>.$FSI_0004.main@() in P:\proj\Tachograph\Project\CompuTachTest\CompuTachTest\rsaTest.fsx:line 16 However, if I change rsaTest2 from a value into a function and call it, let rsaTest2 () = let ecKey = [|0uy..143uy|] // junk data for testing let rsa = RSAParameters(Modulus = ecKey.[8..8+128-1], Exponent = ecKey.[136..136+8-1]) rsa let x = rsaTest2 () then there is no error. F# bug or my mistake?

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• Scala and the Java Memory Model

  - by Ben Lings

  The Java Memory Model (since 1.5) treats final fields differently to non-final fields. In particular, provided the this reference doesn't escape during construction, writes to final fields in the constructor are guaranteed to be visible on other threads even if the object is made available to the other thread via a data race. (Writes to non-final fields aren't guaranteed to be visible, so if you improperly publish them, another thread could see them in a partially constructed state.) Is there any documentation on how/if the Scala compiler creates final (rather than non-final) backing fields for classes? I've looked through the language specification and searched the web but can't find any definitive answers. (In comparison the @scala.volatile annotation is documented to mark a field as volatile)

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• Casting a primitive int to a Number

  - by Tamer

  Let's say that I have the following: int a = 2; Number b = (Number) a; System.out.println(b); // Prints 2 http://java.sun.com/docs/books/jls/first_edition/html/15.doc.html#238146 says that a primitive value may not be cast to a reference type. Does Java know to create an Integer from the primitive int and then cast to the superclass? How exactly does Java handle this behind the scenes? Thanks!

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• In Oracle 10g, how do I see tables in schemes other than system

  - by Yasir Arsanukaev

  In the hr schema there's a table emloyees, I can query data from it specifying it implicitly SELECT count(*) FROM hr.employees while logged in as system, but when I navigate to Home-Object Browser in the browser I can't see the table employees and other tables in other schemas. Can I manage tables in schemas other than system while logged in as system? Maybe there's some setting which enables me to group tables by schema. My Oracle Database version is 10.2.0.1 Express Edition. IIRC I could see all tables in Oracle Database 10.1.x.y. Thanks.

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• Kohana Database Library - How to Execute a Query with the Same Parameters More Than Once?

  - by Noah Goodrich

  With the following bit of code: $builder = ORM::factory('branch')->where('institution_id', $this->institution->id)->orderby('name'); I need to first execute: $count = $builder->count_all(); Then I need to execute: $rs = $builder->find_all($limit, $offset); However, it appears that when I execute the first query the stored query parameters are cleared so that a fresh query can be executed. Is there a way to avoid having the parameters cleared or at least copy them easily without having to reach directly into the Database driver object that stores the query parameters and copy them out? We are using Kohana 2.3.4 and upgrading is not an option.

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• printing parent page and iframe contents from print button withing iframe.

  - by user329094

  I am using an iframe (I hate them by the way!) to call in a 3rd party checkout page into my parent page. The check out page doesn't allow me to pass any variables into it other than $total_amount. So, if an individual purchases 2 or more items they have no record of the items they purchase just the total amount. I have echoed the list of items purchased with php above the iframe for their reference. The final checkout step in the iframe allows you to print the receipt. However, it only prints the iframe content. Can you tell a print button within an iframe to print the parent page as well?

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• How can I make an SQL statement that finds unassociated records?

  - by William Calleja

  I have two tables as follows: tblCountry (countryID, countryCode) tblProjectCountry(ProjectID, countryID) The tblCountry table is a list of all countries with their codes and the tblProjectCountry table associates certain countries with certain projects. I need an SQL statement that gives me a list of the countries with their country code that do NOT have an associated record in the tblProjectCountry table. so far I got to here: SELECT tblCountry.countryID, tblCountry.countryCode FROM tblProjectCountry INNER JOIN tblCountry ON tblProjectCountry.countryID = tblCountry.countryID WHERE (SELECT COUNT(ProjectID) FROM tblProjectCountry WHERE (ProjectID = 1) AND (countryID = tblCountry.countryID)) = 0 The above statement parses as correct but doesn't give the exact result I'm looking for. Can anyone help?

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• Expected specifier-qualifier-list before ... only in classes in a certain folder

  - by funkybro

  Hi Classes in my iPhone project are organised within folders on the filesystem, these correspond to groups (for each folder) in xcode. My problem is that there seems to be a particular class which classes in a particular group/folder cannot make reference to; the compiler complains of "Expected specifier-qualifier-list...". This happens on any class within this group, and also when I create a new class within this group and try and import the offending class like so: #import <Foundation/Foundation.h> #import "MyClass.h" @interface TryingToImport : NSObject { MyClass *myClass; // Expected specifier-qualifier-list before 'MyClass' } Creating an identical class in any other group works OK. I understand this error message is usually due to cyclical import references, I have checked over and over and there don't seem to be any of these. I assume I have inadvertantly configured the offending group to be different to the others in some way but I can't figure out how. Help please!

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• Is there anything wrong with my Factory class?

  - by Alex

  class PieceFactory { @SuppressWarnings("rawtypes") public Piece createPiece(String pieceType) throws Throwable{ Class pieceClass = Class.forName(pieceType); Piece piece = (Piece) pieceClass.newInstance(); return piece; } } I'm not all used to handling exceptions yet therefore I'm just throwing them, but everywhere I use a method that uses this factory it tells me I have to throw exceptions like throwable. For example, in one of my classes I have a method that instantiates a lot of objects using the method that uses the factory. I can use the method in that class by just throwing the exception, however it won't work if I try to pass a reference to that class to another class and then use the method from there. Then it forces me to try catch the exception. I probably don't need a factory but it seemed interesting and I'd like to try to use patterns. The reason I created the factory was that I have 6 subclasses of Piece and I wan't to use a method to instantiate them by passing the type of subclass I want as an argument to the method.

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• Can anyone telme whats wrong in this part of code

  - by Mobin

  string name = ((DateTimePicker)sender).Name.ToString(); name = name.Substring(0, name.Length - 1); name = name + "4"; TimeSpan duration = new TimeSpan(); duration = ((DateTimePicker)sender).Value - ((DateTimePicker)panel2.Controls[name]).Value; name = name.Substring(0, name.Length - 1); name = name + "6"; ((MaskedTextBox)panel2.Controls[name]).Text = duration.ToString(); on execution it gives me Object reference not set to instance of an object similar functionality is used on other places but can't find out what i have to reinitialize here :$

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• How to select the first element of a set with JSTL?

  - by Sergio del Amo

  I managed to do it with the next code but there must be an easier way. <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %> <c:if test="${fn:length(attachments) > 0}"> <c:forEach var="attachment" items="${attachments}" varStatus="loopCount"> <c:if test="${loopCount.count eq 1}"> attachment.id </c:if> </c:forEach> </c:if>

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• Concurency issues with scheduling app

  - by Sazug

  Our application needs a simple scheduling mechanism - we can schedule only one visit per room for the same time interval (but one visit can be using one or more rooms). Using SQL Server 2005, sample procedure could look like this: CREATE PROCEDURE CreateVisit @start datetime, @end datetime, @roomID int AS BEGIN DECLARE @isFreeRoom INT BEGIN TRANSACTION SELECT @isFreeRoom = COUNT(*) FROM visits V INNER JOIN visits_rooms VR on VR.VisitID = V.ID WHERE @start = start AND @end = [end] AND VR.RoomID = @roomID IF (@isFreeRoom = 0) BEGIN INSERT INTO visits (start, [end]) VALUES (@start, @end) INSERT INTO visits_rooms (visitID, roomID) VALUES (SCOPE_IDENTITY(), @roomID) END COMMIT TRANSACTION END In order to not have the same room scheduled for two visits at the same time, how should we handle this problem in procedure? Should we use SERIALIZABLE transaction isolation level or maybe use table hints (locks)? Which one is better?

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• Why can't I store a float value - it's always zero!

  - by just_another_coder

  I have a view controller that is created by the app delegate - it's the first one shown in the app. In its interface I declare float lengthOfTime; I also set it as a property: @property (nonatomic) float lengthOfTime; And in it's implemetation: @synthesize lengthOfTime; In the class viewDidLoad method, I set the value: self.lengthOfTime = 3.0f; However, after this, the value is always zero. No errors, no compile warnings, nothing. Just zero. The class is instantiated, it is showing in the view, so I'm pretty sure it's not a nil reference. I've searched all over Google and can't figure it out. What's going on?!? :(

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• Actionscript classes to 1 SWC file

  - by Daryl

  I'm using Flash Builder 4 (the version after Flex Builder 3, so very similar to Flex Builder 3) and have a bunch of actionscript classes that I frequently need to reference. I have them in a separate folder/package to keep things clean. I know that it's possible to create a SWC from these actionscript files. My question is how do I do it in Flash Builder 4 or Flex Builder 3. Do I need other tools? My objective is just to use the SWC in the project and keep things clean instead of dragging around all these files.

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• How to set the same column width in a datagrid in flex at runtime?

  - by Ra

  HI, In flex, I have a datagrid with 22 columns. I initially display all the columns. The width of each column right is uniform. Now when i change the visiblity of a few columns, the width of each column varies. How do i maintain a uniform column width for each column whether or not there are any invisible columns?... Also how do i get the count of number of visible columns. the ColumnCount property returns total number of columns and not the number of visible ones.

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• T-SQL foreign key check constraint

  - by PaN1C_Showt1Me

  When you create a foreign key constraint in a table and you create the script in MS SQL Management Studio, it looks like this. ALTER TABLE T1 WITH CHECK ADD CONSTRAINT FK_T1 FOREIGN KEY(project_id) REFERENCES T2 (project_id) GO ALTER TABLE T1 CHECK CONSTRAINT FK_T1 GO What I don't understand is what purpose has the second alter with check constraint. Isn't creating the FK constraint enough? Do you have to add the check constraint to assure reference integrity ? Another question: how would it look like then when you'd write it directly in the column definition? CREATE TABLE T1 ( my_column INT NOT NULL CONSTRAINT FK_T1 REFERENCES T2(my_column) ) Isn't this enough?

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• CouchDB Map/Reduce raises execption in reduce function?

  - by fuzzy lollipop

  my view generates keys in this format ["job_id:1234567890", 1271430291000] where the first key element is a unique key and the second is a timestamp in milliseconds. I run my view with this elapsed_time?startkey=["123"]&endkey=["123",{}]&group=true&group_level=1 and here is my reduce function, the intention is to reduce the output to get the earliest and latest timestamps and return the difference between them and now function(keys,values,rereduce) { var now = new Date().valueOf(); var first = Number.MIN_VALUE; var last = Number.MAX_VALUE; if (rereduce) { first = Math.max(first,values[0].first); last = Math.min(last,values[0].last); } else { first = keys[0][0][1]; last = keys[keys.length-1][0][1]; } return {first:now - first, last:now - last}; } and when processing a query it constantly raises the following execption: function raised exception (new TypeError("keys has no properties", "", 1)) I am making sure not to reference keys inside my rereduce block. Why does this function constantly raise this exception?

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• How do I detect a loop in this linked list?

  - by jjujuma

  Say you have a linked list structure in Java. It's made up of Nodes: class Node { Node next; // some user data } and each Node points to the next node, except for the last Node, which has null for next. Say there is a possibility that the list can contain a loop - i.e. the final Node, instead of having a null, has a reference to one of the nodes in the list which came before it. What's the best way of writing boolean hasLoop(Node first) which would return true if the given Node is the first of a list with a loop, and false otherwise? How could you write so that it takes a finite amount of space and a reasonable amount of time?

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• Sql Calculation And Sort By Date

  - by mahesh

  I have Confusion against utilize If,Else Statement against calculation of stock By date. And sort the same by date. There is real challenge to calculate running total between equal date: If date is equal If date is greater than If date is less than My Table Schema Is: TransID int, Auto Increment Date datetime, Inwards decimal(12,2) Outward decimal(12,2) Suppose If I have Records as Below: TransID Date(DD/MM/YYYY) Inward Outward 1 03/02/2011 100 2 12/04/2010 200 3 03/02/2011 400 Than Result Should be: TransID Date(DD/MM/YYYY) Inward Outward Balance 1 03/02/2011 100 -100 2 12/04/2010 200 -300 3 03/02/2011 400 100 I wants to calculate Inward - outwards = Balance and Balance count as running total as above. but the condition that it should be as per date order How to sort and calculate it by date and transID? What is transact SQL IN SQL_SERVER-2000**?.

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• PHP mySQL - select unique value that not being used from dirrefent table

  - by apis17

  Updates : Please see below i have table: data +-----------------------+--------------+-----------+ | State | d_country | d_postcode| +-----------------------+--------------+-----------+ | State1 | Country1 | 1111 | | State2 | Country2 | 2222 | | State3 | Country3 | 3333 | | State4 | Country4 | 4444 | +-----------------------+--------------+-----------+ And another table: user +-----------------------+--------------+-----------+ | Name | u_country | u_postcode| +-----------------------+--------------+-----------+ | Name1 | Country3 | 3333 | | Name2 | Country5 | 5555 | | Name3 | | 6666 | | Name4 | Country6 | 6666 | | Name5 | Country6 | 6666 | +-----------------------+--------------+-----------+ What SQL should i use to: Determine the number (count) of country that are not listed on table data. For example u_postcode is not listed in d_postcode is 5555 and 6666. It will return 2. List down name and what country not available in table data yet. Updates I want to use grouping to filter postcode and make Name3 and Name4 as different rows. For example: +-----------------------+--------------+-----------+ | Name | u_country | u_postcode| +-----------------------+--------------+-----------+ | Name2 | Country5 | 5555 | | Name3 | | 6666 | | Name4 | Country6 | 6666 | +-----------------------+--------------+-----------+ Any possible idea?

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• Jquery and binding an event to an iframe

  - by dbr

  **I'm currently using a jquery textselect plugin to fire alerts based on the selection text anywhere on the page and it works just fine doing something like: $(document).ready(function() { $(document).bind('textselect', function(e) { alert(e.text); }); }); I've since had to add an iframe to the page and I need the text selection to work on text within the iframe as well. I'm trying to do something like this but it's not working: $(document).ready(function() { $('#iframeId').load(function() { $(document.getElementById("iframeId").contentWindow).bind('textselect',function(e) { alert(e.text); }); }); At this point I've tried a whole mess of ways to reference the iframe document without any success. Any ideas?**

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