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• Immutability of big objects

  - by Malax

  Hi StackOverflow! I have some big (more than 3 fields) Objects which can and should be immutable. Every time I run into that case i tend to create constructor abominations with long parameter lists. It doesn't feel right, is hard to use and readability suffers. It is even worse if the fields are some sort of collection type like lists. A simple addSibling(S s) would ease the object creation so much but renders the object mutable. What do you guys use in such cases? I'm on Scala and Java, but i think the problem is language agnostic as long as the language is object oriented. Solutions I can think of: "Constructor abominations with long parameter lists" The Builder Pattern Thanks for your input!

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• Exception handling in Boost.Asio

  - by Alex B

  Boost.Asio documentation suggests the following exception handling pattern: boost::asio::io_service io_service; ... for (;;) { try { io_service.run(); break; // run() exited normally } catch (my_exception& e) { // Deal with exception as appropriate. } } The problem with it is that the context of exception is lost at the point when it's handled. For example, if I have multiple socket sessions going on, I don't know which one caused the exception to be thrown. What would be a better way to handle the exceptions from asynchronous handlers without wrapping them in try/catch blocks?

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• Random directions, with no repeat.. (Bad Description)

  - by Neurofluxation

  Hey there, So I'm knocking together a random pattern generation thing. My code so far: int permutes = 100; int y = 31; int x = 63; while (permutes > 0) { int rndTurn = random(1, 4); if (rndTurn == 1) { y = y - 1; } //go up if (rndTurn == 2) { y = y + 1; } //go down if (rndTurn == 3) { x = x - 1; } //go right if (rndTurn == 4) { x = x + 1; } //go left setP(x, y, 1); delay(250); } My question is, how would I go about getting the code to not go back on itself? e.g. The code says "Go Left" but the next loop through it says "Go Right", how can I stop this? NOTE: setP turns a specific pixel on. Cheers peoples!

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• MVVM View reference to ViewModel

  - by BrettRobi

  I'm using MVVM in a WPF app. I'm very new to both. Let me state that I am not a purest in the MVVM pattern, I am trying to use as many best practices as I can but am trying to make what I think are reasonable compromises to make it work in our environment. For example, I am not trying to achieve 0% code in my View codebehind. I have a couple of questions about best practices. 1) I understand I don't want my VM to know about the attached View, but is it reasonable for the View to have a reference to its VM? 2) If a control in a View opens another View (such as a dialog) should I handle this in the View? It seems wrong to handle it in the VM since then the VM has some knowledge of a specific View.

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• How to access File over the Network

  - by Polo

  Hi! I am having a hard time on this one, I have a folder over the network with public access (no credential restriction). I am trying to do a File.Exist or Directory.Exist and I keep on having a exception. Can someone tell me the good way to do IO over the network. EDIT 1 FOR DETAILS: if i do execture = \agoodip\Public\test.txt I get the file etc etc In my code it look like a basic Directory.Exist(@"\\agoodip\Public") or File.exist(@"\\agoodip\Public\test.txt") The exception I get is Path not found. EDIT 2 : I am using Silverlight 3, Is there any security pattern to be aware of to lookup file on the network? Thanks!

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• Is there any benefit to declaring a private property with a getter and setter?

  - by AmoebaMan17

  I am reviewing another developer's code and he has written a lot of code for class level variables that is similar to the following: /// <summary> /// how often to check for messages /// </summary> private int CheckForMessagesMilliSeconds { get; set; } /// <summary> /// application path /// </summary> private string AppPath { get; set; } Doesn't coding this way add unnecessary overhead since the variable is private? Am I not considering a situation where this pattern of coding is required for private variables?

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• Pass a captured named regular expression to URL dictionary in generic view

  - by Trent Jurewicz

  I am working with a generic view in Django. I want to capture a named group parameter in the URL and pass the value to the URL pattern dictionary. For example, in the URLConf below, I want to capture the parent_slug value in the URL and pass it to the queryset dictionary value like so: urlpatterns = patterns('django.views.generic.list_detail', (r'^(?P<parent_slugs>[-\w])$', 'object_list', {'queryset':Promotion.objects.filter(category=parent_slug)}, 'promo_promotion_list'), ) Is this possible to do in one URLConf entry, or would it be wiser if I create a custom view to capture the value and pass the queryset directly to the generic view from my overridden view?

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• Django - Tips to avoid repeating code in views

  - by D Roddis

  I'm moving from a PHP background into Django development via python, mostly for the sake of tackling a MVC (or MVT) that I feel makes the most sense, although in this pattern I've started to notice a lot of repeated code in my views. For example, when logged in I have information regarding the user that I would like to appear on every page, although when using render_to_response and in every view this is required I have to grab the information and pass it to the render_to_response function. I'm wondering what would be the most efficient way to cut down on the duplicate code which would in essence be required in all views in a particular app. Thanks in advance.

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• What can I use the Google App Engine for?

  - by Sergio Boombastic

  This question possibly doesn't belong here. We'll see how the answers pan out, if this doesn't belong here please move it to where it belongs. I'm following the getting started guide for Google App Engine, and I'm seeing what it can and can't do. Basically, I'm seeing it's very similar to an MVC pattern. You create your model, then create a View that uses that Model to display information. Not only that, but it uses a controller of some kind in this fashion: application = webapp.WSGIApplication( [('/', MainPage)], debug=True) My question is, why would you use this Google App Engine if it's the same as using a number of other MVC frameworks? Is the only benefit you gain the load balancing being handled by Google automagically? What is a good example of something you would need the App Engine for? I'm trying to learn, so thanks for the discussion.

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• Looking for a good explanation of the table generation macro idiom

  - by detly

  I want to make this clear up front : I know how this trick works, what I want is a link to a clear explanation to share with others. One of the answers to a C macro question talks about the "X macro" or "not yet defined macro" idiom. This involves defining something like: #define MAGIC_LIST \ X(name_1, default_1) \ X(name_2, default_2) \ ... Then to create, say, an array of values with named indices you do: typedef enum { #define X(name, val) name, MAGIC_LIST #undef X } NamedDefaults; You can repeat the procedure with a different #define for X() to create an array of values, and maybe debugging strings, etc. I'd like a link to a clear explanation of how this works, pitched at someone who is passably familiar with C. I have no idea what everyone usually calls this pattern, though, so my attempts to search the web for it have failed thus far. (If there is such an explanation on SO, that'd be fine...)

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• Data access strategy for a site like SO - sorted SQL queries and simultaneous updates that affect th

  - by Kaleb Brasee

  I'm working on a Grails web app that would be similar in access patterns to StackOverflow or MyLifeIsAverage - users can vote on entries, and their votes are used to sort a list of entries based on the number of votes. Votes can be placed while the sorted select queries are being performed. Since the selects would lock a large portion of the table, it seems that normal transaction locking would cause updates to take forever (given enough traffic). Has anyone worked on an app with a data access pattern such as this, and if so, did you find a way to allow these updates and selects to happen more or less concurrently? Does anyone know how sites like SO approach this? My thought was to make the sorted selects dirty reads, since it is acceptable if they're not completely up to date all of the time. This is my only idea for possibly improving performance of these selects and updates, but I thought someone might know a better way.

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• what happens to running/blocked runnables when executorservice is shutdown()

  - by prmatta

  I posted a question about a thread pattern today, and almost everyone suggested that I look into the ExecutorService. While I was looking into the ExecutorService, I think I am missing something. What happens if the service has a running or blocked threads, and someone calls ExecutorService.shutdown(). What happens to threads that are running or blocked? Does the ExecutorService wait for those threads to complete before it terminates? The reason I ask this is because a long time ago when I used to dabble in Java, they deprecated Thread.stop(), and I remember the right way of stopping a thread was to use sempahores and extend Thread when necessary: public void run () { while (!this.exit) { try { block(); //do something } catch (InterruptedException ie) { } } } public void stop () { this.exit = true; if (this.thread != null) { this.thread.interrupt(); this.thread = null; } } How does ExecutorService handle running threads?

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• IIS7 301 Redirect from a List of URLs

  - by corymathews

  Recent changes are forcing me to add a bunch of 301 redirects. Seems that IIS7 is my best bet as compared to redirects within the files. I have found how to add them 1 by 1 but this requires the page/folder to exist (which most don't anymore(and creating them seems to defeat the point of the redirect)) and does not work on dynamic urls. I also cannot go to every page and add the redirects at the page level because some older pages are in php which is no longer supported on the new server. There is also no obvious pattern to the changes so each one must be made on its own. samples of the redirects page.htm - /page/ /folder/folder/ - /folder/folder.cfm /folder/folder/ - /folder/ /page.php?id=1 - page.htm

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• Can you use data binding with the Content property of a WPF Frame?

  - by dthrasher

  I can use data binding to set the initial Content of a WPF Frame, but subsequent changes to the the bound property (implemented using INotifyPropertyChange) do not seem to change the content. Also, does anyone know if binding directly to the Content property in this way will cause the bound item to appear in the Frame or NavigationWindow's journal? Some context: I realize that I should probably be using the NavigationService to interact with the Frame, but I'm attempting to follow the MVVM pattern. It seems like it would be much simpler to databind to the Content property...

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• VB.net: Custom ' TODO: List on an Interface

  - by Shiftbit

  How do I add my own todo and comments list to appear on Interfaces? I want it to pop up like IDisposable does: Public Class Foo : Implements IDisposable Private disposedValue As Boolean = False ' To detect redundant calls ' IDisposable Protected Overridable Sub Dispose(ByVal disposing As Boolean) If Not Me.disposedValue Then If disposing Then ' TODO: free other state (managed objects). End If ' TODO: free your own state (unmanaged objects). ' TODO: set large fields to null. End If Me.disposedValue = True End Sub #Region " IDisposable Support " ' This code added by Visual Basic to correctly implement the disposable pattern. Public Sub Dispose() Implements IDisposable.Dispose ' Do not change this code. Put cleanup code in Dispose(ByVal disposing As Boolean) above. Dispose(True) GC.SuppressFinalize(Me) End Sub #End Region End Class Whenever I enter my own comments and todo list they are never autogenerated like IDisposable Interface does. I would like my own Interfaces to preserve the comments so that I can share my Interfaces with in source documentation.

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• Rails: common approach for handling exceptions in restful actions on objects that have been destroye

  - by Greg

  It is very common in Rails for an objects_controller controller to have RESTful edit and destroy actions like so: def edit @object = Object.find(params[:id]) end def destroy @object = Object.find(params[:id]) @object.destroy redirect_to :back end With an associated view that provides edit and destroy links like so: <%= link_to "Edit the Object", edit_object_path(object) %> <%= link_to "Delete", object, :confirm => 'Are you sure?', :method => :delete %> And it is easy to blow this up. If I open two browser windows, A and B, destroy an object with the "Delete" link in browser A and then press the "Edit" link in browser B, the find() in the edit action throws an exception. Obviously there are several ways to deal with this in the edit action: catch the exception and recover gracefully use @object = find(:first, "conditions... etc. and test the @object before going further But seeing as this is such a common pattern, I would love to know how other folks deal with this situation.

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• emacs: inverse search

  - by Data

  Is there a way to do a inverse search? I have very big log file where a particular pattern fills up for few dozen pages 20100414 alpha beta 20100414 alpha beta <few dozen pages> 20100414 alpha beta 20100414 gamma delta 20100414 gamma delta <few dozen pages> 20100414 gamma delta Problem is, I don't know what text would be after "alpha beta". It could be "gamma delta" or something else. So I would like to skip all the lines that contain "alpha beta".

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• how to start animation using MVVM?

  - by Kishore Kumar

  I am converting my exising Application using WPF using MVVM pattern. I have different storyboards in my view . eg. 1. showing splashscreen while loading the app 2. while clicking Menu Toggle button/Radio Button to show the slide in and Slide out animation effect 3. And different mouseover effect for different elements available in the View. How will i call the storyboard using MVVM and which is the best method?. To show the mouse over effect do we really have to use MVVM or code behind?

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• When and why will an OS initialise memory to 0xCD, 0xDD, etc. on malloc/free/new/delete?

  - by LeopardSkinPillBoxHat

  I know that the OS will sometimes initialise memory with certain patterns such as 0xCD and 0xDD. What I want to know is when and why this happens. When Is this specific to the compiler used? Do malloc/new and free/delete work in the same way with regard to this? Is it platform specific? Will it occur on other operating systems, such as Linux or VxWorks? Why My understanding is this only occurs in Win32 debug configuration, and it is used to detect memory overruns and to help the compiler catch exceptions. Can you give any practical examples as to how this initialisation is useful? I remember reading something (maybe in Code Complete 2) that it is good to initialise memory to a known pattern when allocating it, and certain patterns will trigger interrupts in Win32 which will result in exceptions showing in the debugger. How portable is this?

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• Is it a bad idea to have a login dialog inside an iframe?

  - by AyKarsi

  We're creating a website where we will be giving out code snippets to our users which they can place on their own websites. These snippets contain a link a javascript include. When clicking the link, an iframe containing the login dialog to our site opens. The user then authenticates inside the iframe, does his work and when he leaves the iframe his session is closed. We've got it working allready and it's very slick. Our main concern though is phishing. The user has absolutely now way of veryifying where the login page is really coming from. On the other hand, phising attacks are also succesfull even if the user can see the fake-url in the address bar. Would you enter your (OpenId) credentials in an iframe? Does anyone know a pattern with which we could minimise the chances of a phishing attack?

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• How to check connection leak using regular expression ?

  - by gauravkarnatak

  I have to check connection leak in my application i.e. open connections which have not been closed. After searching, after I found out that a thousands times connections have been opened but I can't manually go to each and every code fragment and check for connection close thing. I think, it could be possible using a regular expression but the fact is, I am not that well versed with regex that I could write one. Please suggest a regular expression for checking in a no of java files that a opened connection has been closed or not. My code pattern is something like this. try { /* Some code goes here */ con = EJBUtil.getConnection(JNDI_NAME); /* Some code goes here */ } finally { /* Some code goes here */ DBUtil.close(con); or closeConnection.close(con); /* Some code goes here */ }

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• Can we create a class from a xml file ?

  - by panzerschreck

  Hello, Is it possible to create a class dynamically by reading an xml file ( in java preferably) ? if yes, please provide pointers on how to do it. In the process of development, we have come up with a class that has 5 attributes, all these attributes correspond to an entry in the xml file, now if the user adds/modifies the xml entry the object corresponding to it must change automatically, one approach would be generate the source code, before compile time.Is there any other way ? Is there any common pattern to model such changes in the system ? Thanks,

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• modrewrite RewriteRule problem

  - by timpone

  I am using Apache 2.2 and mod_rewrite. I would like to take the following urls and map them to another url. The pattern is simple and like this: http://domain/test/ex1.html - http://domain/app/index.php/content/?name=ex1 I tried the following in an .htaccess file: RewriteEngine On RewriteBase /app/ RewriteRule (.*)\.html index.php/content/?name=$1 and RewriteEngine On RewriteRule (.*)\.html /app/index.php/content/?name=$1 I wasn't sure if the backreference was correct so set to $0 and $2 but never seemed to help. I also tried setting the RewriteLogLevel to 9. There is a step where it is almost there: rewrite 'ex1.html' - 'index.php/content/?name=ex1' The last line of the rewrite log is as follows: [perdir /var/www/domain/htdocs/test/] internal redirect with /app/index.php/content/ [INTERNAL REDIRECT] How can I get this to rewrite to /app/index.php/content/?name=ex1 ? thanks

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• C# event or delegate or other solution?

  - by user295734

  Looking for some help or programmng ideas or mayeb there is some pattern that would help. Have an application that needs to fire alot of events sequentially, it could up to 100 or more unique events, it will be dynamic depeneding on the situation. Trying to find the best practice for doing this. My main idea right now is to create a list of objects iterate thru them, and fire each event. This seems wrong, or bad practice. Or maybe have one object and pass a list or params into one event? Or am I missing some feature in .NET that i could be using or implementing?

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• Restrict violation of architecture - asp.net MVP

  - by Srikanth

  If we had a defined hierarchy in an application. For ex a 3 - tier architecture, how do we restrict subsequent developers from violating the norms? For ex, in case of MVP (not asp.net MVC) architecture, the presenter should always bind the model and view. This helps in writing proper unit test programs. However, we had instances where people directly imported the model in view and called the functions violating the norms and hence the test cases couldn't be written properly. Is there a way we can restrict which classes are allowed to inherit from a set of classes? I am looking at various possibilities, including adopting a different design pattern, however a new approach should be worth the code change involved.

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