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  • What is so bad about Singletons

    - by Ewan Makepeace
    The Singleton pattern is a fully paid up member of the GoF Patterns Book but lately seems rather orphaned by the developer world. I still use quite a lot of singletons, especially for Factory classes, and while you have to be a bit careful about multithreading issues (like any class actually) fail to see why they are so awful. This site especially seems to assume that everyone agrees that Singletons are evil. Why?

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  • c++ class member functions instatiated by traits

    - by Jive Dadson
    I am reluctant to say I can't figure this out, but I can't figure this out. I've googled and searched stackoverflow, and come up empty. The abstract, and possibly overly vague form of the question is, how can I use the traits-pattern to instantiate non-virtual member functions? The question came up while modernizing a set of multivariate function optimizers that I wrote more than 10 years ago. The optimizers all operate by selecting a straight-line path through the parameter space away from the current best point (the "update"), then finding a better point on that line (the "line search"), then testing for the "done" condition, and if not done, iterating. There are different methods for doing the update, the line-search, and conceivably for the done test, and other things. Mix and match. Different update formulae require different state-variable data. For example, the LMQN update requires a vector, and the BFGS update requires a matrix. If evaluating gradients is cheap, the line-search should do so. If not, it should use function evaluations only. Some methods require more accurate line-searches than others. Those are just some examples. The original version instantiates several of the combinations by means of virtual functions. Some traits are selected by setting mode bits that are tested at runtime. Yuck. It would be trivial to define the traits with #define's and the member functions with #ifdef's and macros. But that's so twenty years ago. It bugs me that I cannot figure out a whiz-bang modern way. If there were only one trait that varied, I could use the curiously recurring template pattern. But I see no way to extend that to arbitrary combinations of traits. I tried doing it using boost::enable_if, etc.. The specialized state info was easy. I managed to get the functions done, but only by resorting to non-friend external functions that have the this-pointer as a parameter. I never even figured out how to make the functions friends, much less member functions. The compiler (vc++ 2008) always complained that things didn't match. I would yell, "SFINAE, you moron!" but the moron is probably me. Perhaps tag-dispatch is the key. I haven't gotten very deeply into that. Surely it's possible, right? If so, what is best practice?

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  • Succinct But Complete Example of WPF App?

    - by Eric J.
    Is there a succinct but complete example project or tutorial that brings together the pieces of the Microsoft stack for a complete application? WPF MVVM Business Objects EF Database I find plenty for WPF and plenty for EF, but am having trouble fully understanding how the EF generated classes relate to business objects, and how those business objects in turn fit into the MVVM pattern.

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  • text replace with regex in sqlserver

    - by Thiyaneshwaran S
    Currently i have sql-server nvarchar(max) column which has text that starts with """ The only thing that varies in the pattern is the < in the class name. The common part is "" Some sample values are "" "" "" All the These span text are present only at the beginning of the column. Any such matching span in the middle should not be removed or matched. Whats the sql server query with regex to remove all these occurance of span?

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  • Stored procedure performance randomly plummets; trivial ALTER fixes it. Why?

    - by gWiz
    I have a couple of stored procedures on SQL Server 2005 that I've noticed will suddenly take a significantly long time to complete when invoked from my ASP.NET MVC app running in an IIS6 web farm of four servers. Normal, expected completion time is less than a second; unexpected anomalous completion time is 25-45 seconds. The problem doesn't seem to ever correct itself. However, if I ALTER the stored procedure (even if I don't change anything in the procedure, except to perhaps add a space to the script created by SSMS Modify command), the completion time reverts to expected completion time. IIS and SQL Server are running on separate boxes, both running Windows Server 2003 R2 Enterprise Edition. SQL Server is Standard Edition. All machines have dual Xeon E5450 3GHz CPUs and 4GB RAM. SQL Server is accessed using its TCP/IP protocol over gigabit ethernet (not sure what physical medium). The problem is present from all web servers in the web farm. When I invoke the procedure from a query window in SSMS on my development machine, the procedure completes in normal time. This is strange because I was under the impression that SSMS used the same SqlClient driver as in .NET. When I point my development instance of the web app to the production database, I again get the anomalous long completion time. If my SqlCommand Timeout is too short, I get System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. Question: Why would performing ALTER on the stored procedure, without actually changing anything in it, restore the completion time to less than a second, as expected? Edit: To clarify, when the procedure is running slow for the app, it simultaneously runs fine in SSMS with the same parameters. The only difference I can discern is login credentials (next time I notice the behavior, I'll be checking from SSMS with the same creds). The ultimate goal is to get the procs to sustainably run with expected speed without requiring occasional intervention. Resolution: I wanted to to update this question in case others are experiencing this issue. Following the leads of the answers below, I was able to consistently reproduce this behavior. In order to test, I utilize sp_recompile and pass it one of the susceptible sprocs. I then initiate a website request from my browser that will invoke the sproc with atypical parameters. Lastly, I initiate a website request to a page that invokes the sproc with typical parameters, and observe that the request does not complete because of a SQL timeout on the sproc invocation. To resolve this on SQL Server 2005, I've added OPTIMIZE FOR hints to my SELECT. The sprocs that were vulnerable all have the "all-in-one" pattern described in this article. This pattern is certainly not ideal but was a necessary trade-off given the timeframe for the project.

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  • Do we need seperate file path for window and linux in java

    - by Kishor Sharma
    I have a file on linux ubuntu server hosted with path name /home/kishor/project/detail/. When I made a web app in window to upload and download file from specified location i used path "c:\kishor\projects\detail\" for saving in window. For my surprise when i used window file path name in my server i am still able to get files and upload them, i.e, "c:\kishor\projects\detail\". Can anyone explain why it is working (as window and linux both use different file path pattern).

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  • Undo/Redo using Memento: Stack, Queue or just LinkedList?

    - by serhio
    What is the best having when implementing Memento pattern (for Undo/Redo) in witch collection to Keep Mementos? Basically, I need this(c = change, u = undo, r = redo): 0 *c -1 0 *c -2 -1 0 *c -3 -2 -1 0 <u -2 -1 0 1 *c -3 -2 -1 0 Variants: LinkedList - possible in principle, maybe not optimized. Queue - not adapted for this task, IMO. Stack - not adapted for undo AND redo; Double Stack - maybe optimal, but can't control the undo maximum size.

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  • jQuery UI dialog + WebKit + HTML response with script

    - by Anthony Koval'
    Once again I am faced with a great problem! :) So, here is the stuff: on the client side, I have a link. By clicking on it, jQuery makes a request to the server, gets response as HTML content, then popups UI dialog with that content. Here is the code of the request-function: function preview(){ $.ajax({ url: "/api/builder/", type: "post", //dataType: "html", data: {"script_tpl": $("#widget_code").text(), "widgets": $.toJSON(mwidgets), "widx": "0"}, success: function(data){ //console.log(data) $("#previewArea").dialog({ bgiframe: true, autoOpen: false, height: 600, width: 600, modal: true, buttons: { "Cancel": function() { $(this).dialog('destroy'); } } }); //console.log(data.toString()); $('#previewArea').attr("innerHTML", data.toString()); $("#previewArea").dialog("open"); }, error: function(){ console.log("shit happens"); } }) } The response (data) is: <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <script type="text/javascript">var smakly_widget_sid = 0 ,widgets = [{"cols": "2","rows": "2","div_id": "smakly_widget","wid": "0","smakly_style": "small_image",}, ] </script> <script type="text/javascript" src="/media/js/smak/smakme.js"></script> </head> <body> preview <div id="smakly_widget" style="width:560px;height:550px"> </div> </body> </html> As you see, there is a script to load: smakme.js, somehow it doesn't execute in WebKit-based browsers (I tried in Safari and Chrome), but in Firefox, Internet Explorer and Opera it works as expected! Here is that script: String.prototype.format = function(){ var pattern = /\{\d+\}/g; var args = arguments; return this.replace(pattern, function(capture){ return args[capture.match(/\d+/)]; }); } var turl = "/widget" var widgetCtrl = new(function(){ this.render_widget = function (w, content){ $("#" + w.div_id).append(content); } this.build_widgets = function(){ for (var widx in widgets){ var w = widgets[widx], iurl = '{0}?sid={1}&wid={2}&w={3}&h={4}&referer=http://ya.ru&thrash={5}'.format( turl, smakly_widget_sid, w.wid, w.cols, w.rows, Math.floor(Math.random()*1000).toString()), content = $('<iframe src="{0}" width="100%" height="100%"></iframe>'.format(iurl)); this.render_widget(w, content); } } }) $(document).ready(function(){ widgetCtrl.build_widgets(); }) Is that some security issue, or anything else?

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  • Improving MVP in Scala

    - by Alexey Romanov
    The classical strongly typed MVP pattern looks like this in Scala: trait IView { } trait Presenter[View <: IView] { // or have it as an abstract type member val view : View } case class View1(...) extends IView { ... } case object Presenter1 extends Presenter[View1] { val view = View1(...) } Now, I wonder if there is any nice way to improve on it which I am missing...

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  • How to access 'private functions' in a singleton from another object inside it.

    - by Cedric Dugas
    I am currently trying to create a test suite for my javascript apps. My problem is that, it seems I cannot get access to init() from my utils object, as you can see below: I have my app that follow a singleton pattern: var appModal = function () { var utils = Object.create(moduleUtils); function init(caller, options ) { } }(); My test suite is in moduleUtils, this is a object literal converted to a prototype moduleUtils.debug = { addSlideTest : function(){ /* this function cannot fire init() from appModal */ }}

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  • calling a java servlet from javascript

    - by marco
    Hello, I am trying to create a web application using the MCV design pattern. For the gui part I would like to use javascript. And for the controller Java Servlets. Now I have never really worked with javascript, so I'm having a hard time figuring out how to call a java servlet from javascript and how to get the response from the servlet. Can anybody help me out?

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  • Accessing parent-level controls from inside a ComboBox's child controls

    - by eponymous23
    I have XAML similar to this: <ListBox ItemsSource="{Binding SearchCriteria, Source={StaticResource model}}" SelectionChanged="cboSearchCriterionType_SelectionChanged"> <ListBox.ItemTemplate> <DataTemplate> <StackPanel Name="spCriterion" Orientation="Horizontal" Height="20"> <ComboBox Name="cboSearchCriterionType" Width="120" SelectionChanged="cboSearchCriterionType_SelectionChanged"> <ComboBox.Items> <ComboBoxItem IsSelected="True" Content="Anagram Match" /> <ComboBoxItem Content="Pattern Match" /> <ComboBoxItem Content="Subanagram Match" /> <ComboBoxItem Content="Length" /> <ComboBoxItem Content="Number of Vowels" /> <ComboBoxItem Content="Number of Anagrams" /> <ComboBoxItem Content="Number of Unique Letters" /> </ComboBox.Items> </ComboBox> <TextBox x:Name="SearchSpec" Text="{Binding SearchSpec}" /> <TextBox x:Name="MinValue" Text="{Binding MinValue}" Visibility="Collapsed" /> <TextBox x:Name="MaxValue" Text="{Binding MaxValue}" Visibility="Collapsed" /> </StackPanel> </DataTemplate> </ListBox.ItemTemplate> As you can tell from the markup, I have a listbox that is bound to a collection of SearchCriterion objects (collectively contained in a SearchCriteria object). The idea is that the user can add/remove criterion items from the criteria, each criterion is represented by a listbox item. Inside the listbox item I have a combobox and three textboxes. What I'm trying to do is change the visibility of the TextBox controls depending on the item that is selected in the ComboBox. For example, if the user selects "Pattern Match" then I want to show only the first textbox and hide the latter two; conversely, if the user selects "Length" or any of the "Number of..." items, then I want to hide the first TextBox and show the latter two. What is the best way to achieve this? I was hoping to do something simple in the SelectionChanged event handler for the listbox but the textbox controls are presumably out of the SelectionChanged event's scope. Do I have to programmatically traverse the control hierarchy and find the controls?

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  • vim: Executing a list of editor commands

    - by gveda
    Hi, Is there a way in vim to give a list of editor commands? I want to execute a series of 'global' commands, and there is some pattern to the commands. So I would ideally like to generate the list of commands (using regex search & substitute), and then run them, instead of having to type in each command. Thanks! Gaurav

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  • URL Controller Mapping Strategies (PHP)

    - by sunwukung
    This is kind of an academic question, so feel free to exit now. I've had a dig through Stack for threads pertaining to URL/Controller mapping in MVC frameworks - in particular this one: http://stackoverflow.com/questions/125677/php-application-url-routing So far, I can ascertain two practices: 1: dynamic mapping through parsing the URL string (exploded on '/') 2: pattern matching matching url to config file containing available routes I wanted to get some feedback (or links to some other threads/articles) from folks regarding their views on how best to approach this task.

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  • Java: Make a method abstract for each extending class

    - by Martijn Courteaux
    Hi, Is there any keyword or design pattern for doing this? public abstract class Root { public abstract void foo(); } public abstract class SubClass extends Root { public void foo() { // Do something } } public class SubberClass extends SubClass { // Here is it not necessary to override foo() // So is there a way to make this necessary? // A way to obligate the developer make again the override } Thanks

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  • Web user interface. Add new item and list of items

    - by w1z
    Hello all I need your opinion on the following question. It's need to implement the administration web interface to add\change\remove\display system users. I need to display all users and controls for user adding/changing. What is the common pattern in web for this situation: create one page or create two separate pages for displaying and adding/changing users? Thanks, sorry for some possible oddness (:

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