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  • [MySQL] Efficiently store last X records per item

    - by Saif Bechan
    I want to store the last X records in an MySQL database in an efficient way. So when the 4th record is stored the first should be deleted. The way I do this not is first run a query getting the items. Than check what I should do then insert/delete. There has to be a better way to do this. Any suggestions? Edit I think I should add that the records stored do not have a unique number. They have a mixed par. For example article_id and user_id. Then I want to make a table with the last X items for user_x. Just selecting the article from the table grouped by user and sorted by time is not an option for me. The table where I do the sort and group on has millions of records and gets hit a lot for no reason. So making a table in between with the last X records is way more effient. PS. I am not using this for articles and users.

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  • Is there anything bad in declaring static inner class inside interface in java?

    - by Roman
    I have an interface ProductService with method findByCriteria. This method had a long list of nullable parameters, like productName, maxCost, minCost, producer and so on. I refactored this method by introducing Parameter Object. I created class SearchCriteria and now method signature looks like this: findByCriteria (SearchCriteria criteria) I thought that instances of SearchCriteria are only created by method callers and are only used inside findByCriteria method, i.e.: void processRequest() { SearchCriteria criteria = new SearchCriteria () .withMaxCost (maxCost) ....... .withProducer (producer); List<Product> products = productService.findByCriteria (criteria); .... } and List<Product> findByCriteria(SearchCriteria criteria) { return doSmthAndReturnResult(criteria.getMaxCost(), criteria.getProducer()); } So I did not want to create separate public class for SearchCriteria and put it inside ProductServiceInterface: public interface ProductService { List<Product> findByCriteria (SearchCriteria criteria); static class SearchCriteria { ... } } Is there anything bad in this interface? Where whould you place SearchCriteria class?

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  • Is there a pattern for this?

    - by Timmy
    i have something that requires a matrix of values, similar to pokemon: i have a class object for each of the types, is there a pattern or a good way to implement this, as a middle layer or in the classes?

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  • Unit Testing User Interface. What is an effective way ?

    - by pierocampanelli
    I have an accounting & payroll client/server application where there are several input form with complex data validation rules. I am finding an effective way to perform unit testing of user interface. For complex validation rules I mean: "Disable button X if I Insert a value in textfield Y" "Enable a combobox if I insert a value in a textfield" ...... ...... Most promising pattern i have found is suggested by M. Fowler (http://martinfowler.com/eaaDev/ModelViewPresenter.html). Have you any experience about Unit Testing of User Interface? As technology stack I am using: .NET 3.5 & Windows Forms Widget Library.

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  • Is it good practice to put private API in the .m files and public API in .h files in Cocoa?

    - by Paperflyer
    Many of my classes in my current project have several properties and methods that are only ever called from within the class itself. Also, they might mess with the working of the class depending on the current state of the class. Currently, all these interfaces are defined in the main interface declaration in the .h files. Is it considered good practice to put the “private” methods and properties at the top of the .m files? This won't ever affect anything since I am very likely the only person ever to look at this source code, but of course it would be interesting to know for future projects.

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  • wpf command pattern

    - by evan
    I have a wpf gui which displays a list of information in separate window and in a separate thread from the main application. As the user performs actions in the main window the side window is updated. (For example if you clicked page down in the main window a listbox in the side window would page down). Right now the architecture for this application feels very messy and I'm sure there is a cleaner way to do it. It looks like this: Main Window contains a singleton SideWindowControl which communicates with an instance of the SideWindowDisplay using events - so, for example, the pagedown button would work like: 1) the event handler of the button on the main window calls SideWindowControl.PageDown() 2) in the PageDown() function a event is created and thrown. 3) finally the gui, ShowSideWindowDisplay is subscribing to the SideWindowControl.Actions event handles the event and actually scrolls the listbox down - note because it is in a different thread it has to do that by running the command via Dispatcher.Invoke() This just seems like a very messy way to this and there must be a clearer way (The only part that can't change is that the main window and the side window must be on different threads). Perhaps using WPF commands? I'd really appreciate any suggestions!! Thanks

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  • Question about factory classes

    - by devoured elysium
    Currently I have created a ABCFactory class that has a single method creating ABC objects. Now that I think of it, maybe instead of having a factory, I could just make a static method in my ABC Method. What are the pro's and con's on making this change? Will it not lead to the same? I don't foresee having other classes inherit ABC, but one never knows! Thanks

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  • objectWithFieldNAme Best Practice for CoreData

    - by Rafael
    Hello, I'm trying to implements some methods for my CoreData models and I'm wonndering if the way I'm doing it is a good practice. I want to implement methods of the type getObjectsWithFieldName. This methods could be used by severals views. So the way I'm doing it is implementing a Class method in the model in the following way: +(NSArray *)getObjectWithFieldName:(NSString *)fieldName andContext:(NSManagedObjectContext *) context; Is this a good practice? Or there is another way to do it for iPhone Development? Thanks in advanced.

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  • Best Practice: Software Versioning

    - by Sebi
    I couldn't find a similar question here on SO, but if you find one please link. Is there any guideline or standard best practice how to version a software you develop in your spare time for fun, but nevertheless will be used by some people? I think it's necessary to version such software so that you know about with version one is talking about (e.g. for bug fixing, support, and so on). But where do I start the versioning? 0.0.0? or 0.0? And then how to I increment the numbers? major release.minor change? and should'nt any commit to a version control system be another version? or is this only for versions which are used in a productive manner?

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  • Robust Large File Transfer with WCF

    - by Sharov
    I want to transfer big files (1GB) over unreliable transport channels. When connection is interrupted, I don't want start file transfering from the begining. I can partially store it in a temp table and store last readed position, so when connection is reestablished I can request continue uploading of file from this position. Is there any best-practice for such kind of things. I'm currently use chunking channel.

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  • is this a secure approach in ActiveRecords in Rails?

    - by Adnan
    Hello, I am using the following for my customers to unsubscribe from my mailing list; def index @user = User.find_by_salt(params[:subscribe_code]) if @user.nil? flash[:notice] = "the link is not valid...." render :action => 'index' else Notification.delete_all(:user_id => @user.id) flash[:notice] = "you have been unsubscribed....." redirect_to :controller => 'home' end end my link looks like; http://site.com/unsubscribe/32hj5h2j33j3h333 so the above compares the random string to a field in my user table and accordingly deletes data from the notification table. My question; is this approach secure? is there a better/more efficient way for doing this? All suggestions are welcome.

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  • Converting ASP.NET MVC to n-Tiered Architecture

    - by Jeff
    I just built an application using ASP.NET MVC. The programmers at my company want to build all future modules using n-Tiered (Presentation Layer, Business Logic Layer, Data Access Layer) architecture. I am not the programmer and need to know why this makes sense? Do I have to completely rewrite the entire code or can it be converted? We are building an HRIS system with Business Intelligence. Somebody please explain why or why not this approach does or does not make sense.

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  • What Getters and Setters should and shouldn't do.

    - by cyclotis04
    I've run into a lot of differing opinions on Getters and Setters lately, so I figured I should make it into it's own question. A previous question of mine received an immediate comment (later deleted) that stated setters shouldn't have any side effects, and a SetProperty method would be a better choice. Indeed, this seems to be Microsoft's opinion as well. However, their properties often raise events, such as Resized when a form's Width or Height property is set. OwenP also states "you shouldn't let a property throw exceptions, properties shouldn't have side effects, order shouldn't matter, and properties should return relatively quickly." Yet Michael Stum states that exceptions should be thrown while validating data within a setter. If your setter doesn't throw an exception, how could you effectively validate data, as so many of the answers to this question suggest? What about when you need to raise an event, like nearly all of Microsoft's Control's do? Aren't you then at the mercy of whomever subscribed to your event? If their handler performs a massive amount of information, or throws an error itself, what happens to your setter? Finally, what about lazy loading within the getter? This too could violate the previous guidelines. What is acceptable to place in a getter or setter, and what should be kept in only accessor methods?

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  • HTTP POST with URL query parameters -- good idea or not?

    - by Steven Huwig
    I'm designing an API to go over HTTP and I am wondering if using the HTTP POST command, but with URL query parameters only and no request body, is a good way to go. Considerations: "Good Web design" requires non-idempotent actions to be sent via POST. This is a non-idempotent action. It is easier to develop and debug this app when the request parameters are present in the URL. The API is not intended for widespread use. It seems like making a POST request with no body will take a bit more work, e.g. a Content-Length: 0 header must be explicitly added. It also seems to me that a POST with no body is a bit counter to most developer's and HTTP frameworks' expectations. Are there any more pitfalls or advantages to sending parameters on a POST request via the URL query rather than the request body? Edit: The reason this is under consideration is that the operations are not idempotent and have side effects other than retrieval. See the HTTP spec: In particular, the convention has been established that the GET and HEAD methods SHOULD NOT have the significance of taking an action other than retrieval. These methods ought to be considered "safe". This allows user agents to represent other methods, such as POST, PUT and DELETE, in a special way, so that the user is made aware of the fact that a possibly unsafe action is being requested. ... Methods can also have the property of "idempotence" in that (aside from error or expiration issues) the side-effects of N 0 identical requests is the same as for a single request. The methods GET, HEAD, PUT and DELETE share this property. Also, the methods OPTIONS and TRACE SHOULD NOT have side effects, and so are inherently idempotent.

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  • What is the recommended way of parsing an XML feed with multiple namespaces with ActionScript 3.0?

    - by dafko
    I have seen the following methods to be used in several online examples, but haven't found any documentation on the recommended way of parsing an XML feed. Method 1: protected function xmlResponseHandler(event:ResultEvent):void { var atom:Namespace = new Namespace("http://www.w3.org/2005/Atom"); var microsoftData:Namespace = new Namespace("http://schemas.microsoft.com/ado/2007/08/dataservices"); var microsoftMetadata:Namespace = new Namespace("http://schemas.microsoft.com/ado/2007/08/dataservices/metadata"); var ac:ArrayCollection = new ArrayCollection(); var keyValuePairs:KeyValuePair; var propertyList:XMLList = (event.result as XML)..atom::entry.atom::content.microsoftMetadata::properties; for each (var properties:XML in propertyList) { keyValuePairs = new KeyValuePair(properties.microsoftData::FieldLocation, properties.microsoftData::Locationid); ac.addItem(keyValuePairs); } cb.dataProvider = ac; } Method 2: protected function xmlResponseHandler(event:ResultEvent):void { namespace atom = "http://www.w3.org/2005/Atom"; namespace d = "http://schemas.microsoft.com/ado/2007/08/dataservices"; namespace m = "http://schemas.microsoft.com/ado/2007/08/dataservices/metadata"; use namespace d; use namespace m; use namespace atom; var ac:ArrayCollection = new ArrayCollection(); var keyValuePairs:KeyValuePair; var propertyList:XMLList = (event.result as XML)..entry.content.properties; for each (var properties:XML in propertyList) { keyValuePairs = new KeyValuePair(properties.FieldLocation, properties.Locationid); ac.addItem(keyValuePairs); } cb.dataProvider = ac; } Sample XML feed: <?xml version="1.0" encoding="iso-8859-1" standalone="yes"?> <feed xml:base="http://www.test.com/Test/my.svc/" xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns="http://www.w3.org/2005/Atom"> <title type="text">Test_Locations</title> <id>http://www.test.com/test/my.svc/Test_Locations</id> <updated>2010-04-27T20:41:23Z</updated> <link rel="self" title="Test_Locations" href="Test_Locations" /> <entry> <id>1</id> <title type="text"></title> <updated>2010-04-27T20:41:23Z</updated> <author> <name /> </author> <link rel="edit" title="Test_Locations" href="http://www.test.com/id=1" /> <category term="MySQLModel.Test_Locations" scheme="http://schemas.microsoft.com/ado/2007/08/dataservices/scheme" /> <content type="application/xml"> <m:properties> <d:FieldLocation>Test Location</d:FieldLocation> <d:Locationid>test0129</d:Locationid> </m:properties> </content> </entry> <entry> <id>2</id> <title type="text"></title> <updated>2010-04-27T20:41:23Z</updated> <author> <name /> </author> <link rel="edit" title="Test_Locations" href="http://www.test.com/id=2" /> <category term="MySQLModel.Test_Locations" scheme="http://schemas.microsoft.com/ado/2007/08/dataservices/scheme" /> <content type="application/xml"> <m:properties> <d:FieldLocation>Yet Another Test Location</d:FieldLocation> <d:Locationid>test25</d:Locationid> </m:properties> </content> </entry> </feed>

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  • Tips for Using Multiple Development Systems

    - by Tim Lytle
    When I travel, I don't pack up the desktop I use in the office and take it with me. Maybe I should, but I don't. However, since I'm a contract programmer I like to be able to work wherever I am: I'm mostly thinking of web development here. Version Control goes a long way in keeping sane and working on multiple projects on multiple systems (two or three computers); however, there are the issues of: IDE settings - different display sizes mean the IDE settings can't be completely synced, if at all. Database - if the database is 'external' (even if it's running on the same system, it's not in version control), how do you maintain the needed syncs of structure. Development Stack - Some projects need non-standard extensions, libraries, etc installed. Just an overview of some of the hassle involved with developing on multiple systems. I'll probably end up asking some specific questions, but I thought a CW style tips might reveal some things I would even think to ask about. Update: I guess this would also address tips to make upgrading/replacing your development system easier (something I've just done). So, one tip per answer please, so the 'top' tips are easy to find. How do you make it easier to develop on multiple systems, or to transfer work after upgrading/replaceing a development system?

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  • Best way to unit test Collection?

    - by limc
    I'm just wondering how folks unit test and assert that the "expected" collection is the same/similar as the "actual" collection (order is not important). To perform this assertion, I wrote my simple assert API:- public void assertCollection(Collection<?> expectedCollection, Collection<?> actualCollection) { assertNotNull(expectedCollection); assertNotNull(actualCollection); assertEquals(expectedCollection.size(), actualCollection.size()); assertTrue(expectedCollection.containsAll(actualCollection)); assertTrue(actualCollection.containsAll(expectedCollection)); } Well, it works. It's pretty simple if I'm asserting just bunch of Integers or Strings. It can also be pretty painful if I'm trying to assert a collection of Hibernate domains, say for example. The collection.containsAll(..) relies on the equals(..) to perform the check, but I always override the equals(..) in my Hibernate domains to check only the business keys (which is the best practice stated in the Hibernate website) and not all the fields of that domain. Sure, it makes sense to check just against the business keys, but there are times I really want to make sure all the fields are correct, not just the business keys (for example, new data entry record). So, in this case, I can't mess around with the domain.equals(..) and it almost seems like I need to implement some comparators for just unit testing purposes instead of relying on collection.containsAll(..). Are there some testing libraries I could leverage here? How do you test your collection? Thanks.

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  • Using switch and enumerations as substitute for named methods

    - by MatthewMartin
    This pattern pops up a lot. It looks like a very verbose way to move what would otherwise be separate named methods into a single method and then distinguished by a parameter. Is there any good reason to have this pattern over just having two methods Method1() and Method2() ? The real kicker is that this pattern tends to be invoked only with constants at runtime-- i.e. the arguments are all known before compiling is done. public enum Commands { Method1, Method2 } public void ClientCode() { //Always invoked with constants! Never user input. RunCommands(Commands.Method1); RunCommands(Commands.Method2); } public void RunCommands(Commands currentCommand) { switch (currentCommand) { case Commands.Method1: // Stuff happens break; case Commands.Method2: // Other stuff happens break; default: throw new ArgumentOutOfRangeException("currentCommand"); } }

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  • Java - Calling all methods of a class

    - by Thomas Eschemann
    I'm currently working on an application that has to render several Freemarker templates. So far I have a Generator class that handles the rendering. The class looks more or less like this: public class Generator { public static void generate(…) { renderTemplate1(); renderTemplate2(); renderTemplate3(); } private static void render(…) { // renders the template } private static void renderTemplate1() { // Create config object for the rendering // and calls render(); }; private static void renderTemplate1() { // Create config object for the rendering // and calls render(); }; … } This works, but it doesn't really feel right. What I would like to do is create a class that holds all the renderTemplate...() methods and then call them dynamically from my Generator class. This would make it cleaner and easier to extend. I was thinking about using something like reflection, but it doesn't really feel like a good solution either. Any idea on how to implement this properly ?

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  • How to Communicate between minifb and a GAE-Hosted Silverlight Client

    - by Nick Gotch
    I have a minifb app (technically gminifb) running on Google App Engine with a bunch of handlers for processing all kinds of requests from a Silverlight client. What's the recommended approach for adding the FB GET variables, such as fb_sig, to the HTTP requests? I believe I can technically pass the session key and uid directly and get things to work but it seems there's probably a much better way to do this. I was reading about FBJS AJAX and I'm trying to figure out how I can use it to proxy the HTTP requests from the Silverlight client through it. Is this a good way to do it? And if so, how would I go about doing so? Any other recommendations would be appreciated too. Thanks,

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  • how to share a variable between two threads

    - by prmatta
    I just inherited some code, two threads within this code need to perform a system task. One thread should do the system task before the other thread. They should not be performing the system task together. The two threads do not have references to each other. Now, I know I can use some sort of a semaphore to achieve this. But my question is what is the right way to get both threads to access this semaphore. I could create a static variable/method a new class : public class SharedSemaphore { private static Semaphore s = new Semaphore (1, true); public static void performSystemTask () { s.acquire(); } public static void donePerformingSystemTask() { s.release(); } } This would work (right?) but this doesn't seem like the right thing to do. Because, the threads now have access to a semaphore, without ever having a reference to it. This sort of thing doesn't seem like a good programming practice. Am I wrong?

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