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• How to keep historic details of modification in a database (Audit trail)?

  - by mada

  I'm a J2EE developer & we are using hibernate mapping with a PostgreSQL database. We have to keep track of any changes occurs in the database, in others words all previous & current values of any field should be saved. Each field can be any type (bytea, int, char...) With a simple table it is easy but we a graph of objects things are more difficult. So we have, speaking in a UML point of view, a graph of objects to store in the database with every changes & the user. Any idea or pattern how to do that?

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• php regex replace slashes and spaces and hyphens

  - by Muhammad Shahzad

  I have fews combinations of strings that I need to bring in to one pattern, that is multiple spaces should be removed, double hyphens should be replaced with single hypen, and single space should be replaced with single hyphen. I have already tried this expression. $output = preg_replace( "/[^[:space:]a-z0-9]/e", "", $output ); $output = trim( $output ); $output = preg_replace( '/\s+/', '-', $output ); But this fails in few combinations. I need help in making all of these combinations to work perfectly: steel-black steel- black steel black I should also remove any of these as well "\r\n\t".

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• Inconsistent MySQL COLLATE errors across databases

  - by Teflon Ted

  I have two physically-separate MySQL databases on which I have to run a single query. The query has a section of SQL that looks like this: and foo_table.bar_column like concat('%', rules.pattern, '%') COLLATE utf8_general_ci It runs fine on database A but on database B I get this error: ERROR 1253 (42000): COLLATION 'utf8_general_ci' is not valid for CHARACTER SET 'latin1' If I remove the collation it runs fine on database B but on database A I get this error: ERROR 1267 (HY000): Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation 'like' Is there a version of the query that will run on both databases? Or, is there a configuration I can change on either database to make the query happy in both places? Update: Database A is version 5.1.38, Database B is version 5.1.34

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• How to determine whether a .NET exception is being handled?

  - by romkyns

  We're investigating a coding pattern in C# in which we'd like to use a "using" clause with a special class, whose Dispose() method does different things depending on whether the "using" body was exited normally or with an exception. To the best of my understanding, the CLR keeps track of the current exception being handled until it's been consumed by a "catch" handler. However it's not entirely clear whether this information is exposed in any way for the code to access. Do you know whether it is, and if so, how to access it? For example: using (var x = new MyObject()) { x.DoSomething(); x.DoMoreThings(); } class MyObject : IDisposable { public void Dispose() { if (ExceptionIsBeingHandled) Rollback(); else Commit(); } } This looks almost like System.Transactions.TransactionScope, except that success/failure is not determined by a call to x.Complete(), but rather based on whether the using body was exited normally.

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• Why is 'heroku create' doing nothing?

  - by vlasits

  I opened a heroku account. I followed the instructions on http://docs.heroku.com/quickstart. I have a working rails app which I have deployed successfully elsewhere. I have a github account that works. I have a local git repository for my rails app. I installed the heroku gem. It shows up in my gem list. I typed 'heroku create' at the command prompt... My command console showed that it was thinking about it, but did nothing. No errors. No action. Possible related facts: I am using a Windows 7 machine. I have also failed miserably at deploying with capistrano with a similar--issue command, get no response--pattern.

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• Convert inline image tags like [image:123:title:size] into HTML img tags

  - by Jacques Joubert

  I am looking for help with regular expression $pattern to convert inline image tags like [image:123:title:size] into HTML img tags. here is the code: //[image:ID:caption:size] $content = '[image:38:title:800x900]'; preg_match_all( '/\[image:(\d+)(:?)([^\]]*)\]/i', $content, $images ); if( !empty( $images[0] ) ) { // There are image inline tags in the content foreach( $images[0] as $i => $tag ) { $link_ID = (int)$images[1][$i]; $caption = empty( $images[2][$i] ) ? '#' : $images[3][$i]; $size = empty( $images[4][$i] ) ? '#' : $images[4][$i]; } echo '<br />'; echo 'ID: '.$link_ID.'<br />'; echo 'Tag: '.$caption.'<br />'; echo 'size: '.$size.'<br />'; } which outputs: ID: 12 Tag: caption:size size: # Any help would be great!

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• Insert A Line At The Beginning Of A File

  - by thebourneid

  I'm trying to insert/add a line 'COMMENT DUMMY' at the beginnig of a file as a first row if /PATTERN/ not found. I know how to do this with OPEN CLOSE function. Probably after reading the file it should look something like this: open F, ">", $fn or die "could not open file: $!"; ; print F "COMMENT DUMMY\n", @array; close F; But I have a need to implement this with the use of the Tie::File function and don't know how. use strict; use warnings; use Tie::File; my $fn = 'test.txt'; tie my @lines, 'Tie::File', $fn or die "could not tie file: $!"; untie @lines;

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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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• Is it possible to use Dependency Injection/IoC on an ASP.NET MVC FilterAttribute ?

  - by Pure.Krome

  Hi folks, I've got a simple custom FilterAttribute which I use decorate various ActionMethods. eg. [AcceptVerbs(HttpVerbs.Get)] [MyCustomFilter] public ActionResult Bar(...) { ... } Now, I wish to add some logging to this CustomFilter Action .. so being a good boy, I'm using DI/IoC ... and as such wish to use this pattern for my custom FilterAttribute. So if i have the following... ILoggingService and wish to add this my custom FilterAttribute .. i'm not sure how. Like, it's easy for me to do the following... public class MyCustomFilterAttribute : FilterAttribute { public MyCustomFilterAttribute(ILoggingService loggingService) { ... } } But the compiler errors saying the attribute which decorates my ActionMethod (listed above...) requires 1 arg .. so i'm just not sure what to do :(

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• How to tell when my batch of EAP calls are completed?

  - by codemonkie

  This is following my question: http://stackoverflow.com/questions/2607038/c-how-to-consume-web-service-adheres-to-the-event-based-asynchronous-pattern My program is calling the DoStuffAsync() x many times in a batch, hence the callback will get invoked the same number of times upon OnComplete(). Is there a way to find out when my batch is finished such that I can generate a report on the success/failed results? All I can think of is to have a static count variable for x and deduct 1 every time OnComplete() is called, but its kind of silly and error prone I'm afraid. TIA.

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• Sqlalchemy layout with WSGI application

  - by TheDude

  I'm working on writing a small WSGI application using Bottle and SqlAlchemy and am confused on how the "layout" of my application should be in terms of SqlAlchemy. My confusion is with creating engines and sessions. My understanding is that I should only create one engine with the 'create_engine' method. Should I be creating an engine instance in the global namespace in some sort of singleton pattern and creating sessions based off of it? How have you done this in your projects? Any insight would be appreciated. The examples in the documentation dont seem to make this entirely clear (unless I'm missing something obvious). Any thoughts?

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• GUI system architecture?

  - by topright

  I'm designing GUI (graphical user interface) system for a game engine (C++). Idea is to create a heirarchy of GUI controllers like Focusable, Hoverable, Dragable etc. Every GUI component can attach multiple controllers, they modify component's behaviour. I think it gives flexible system and protects from code duplication. Different instances of the same GUI class can have different complex behaviours (may be, even change it dynamically), so this approach looks practical. The other choice is to add focused, hovered, dragged etc. flags in the base GUI component class. It looks like overhead and not that flexible. Another solution is to use Decorator pattern and wrap objects with FocusDecorator, HoverDecorator etc. Maintaining such system looks a bit harder. Question: What are pitfalls in my solution? May be you have seen a better approaches in GUI systems? What are the best ways of implementing such flexible complex system?

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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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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