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  • Which pattern is best for large project

    - by shamim
    I have several years of software development experience, but I am not a keen and adroit programmer, to perform better I need helping hands. Recently I engaged in an ERP project. For this project want a very effective structure, which will be easily maintainable and have no compromise about performance issue. Below structures are now present in my old projects. Entity Layer BusinessLogic Layer. DataLogic Layer UI Layer. Bellow picture describe how they are internally connected. For my new project want to change my project structure, I want to follow below steps: Core Layer(common) BLL DAL Model UI Bellow picture describe how they are internally connected. Though goggling some initial type question’s are obscure to me, they are : For new project want to use Entity framework, is it a good idea? Will it increase my project performance? Will it more maintainable than previous structure? Entity Framework core disadvantages/benefits are? For my project need help to select best structure. Will my new structure be better than the old one?

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  • Materials from Parallel Programming Pattern Presentation at Charlottesville .NET User Group Meeting

    - by John Blumenauer
    On Thursday, May 27, I had the privilege of presenting “A Look at Parallel Programming Patterns” at the Charlottesville .NET User Group’s monthly meeting.  Those folks in attendance had many great questions and were obviously very interested in what the Parallel Task Library has to offer.  The code and slides can be found HERE.  Thanks again to CHODOTNET for having me in town to speak.  If you experience any problems downloading the slides or code, please let me know.

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  • All in a Day's Work: Unblocking Multiple Downloaded Files with a Single Command

    - by Sam Abraham
    Files downloaded using Internet Explorer retain Internet Zone permission level and hence are “Blocked” by default on Windows 7 machines. Honestly, while an added overhead for developers; I really appreciate this feature as it provides a good protection layer for casual web users. My workaround is to simply unblock the downloaded zip file (if download was a zip file) which, in turn, unblocks the files stored within. Today however, I was left with a situation where I had to “Open” and “Copy” the content rather than “Save” a zip file. That of course left me with a few dozen files I have to manually unblock. A few minutes of internet search lead me to the link below which worked like a charm: 1-Download streams.exe from SystInternals - http://technet.microsoft.com/en-us/sysinternals/bb897440.aspx 2-Go to command prompt (cmd.exe) 3-Navigate to where you have streams.exe installed 4-Use command line switches: streams.exe –s –d “<folder path>” This removed the Internet Zone restrictions from all files under “<folder path>” and its subfolders as well. [Deleted :Zone.Identifier:$DATA] References: http://social.technet.microsoft.com/Forums/en-US/itproxpsp/thread/806f0104-1caa-4a66-b504-7a681d1ccb33/

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  • Design Pattern for Skipping Steps in a Wizard

    - by Eric J.
    I'm designing a flexible Wizard system that presents a number of screens to complete a task. Some screens may need to be skipped based on answers to prompts on one or more previous screens. The conditions to skip a given screen need to be editable by a non-technical user via a UI. Multiple conditions need only be combined with and. I have an initial design in mind, but it feels inelegant. I wonder if there's a better way to approach this class of problem. Initial Design UI where The first column allows the user to select a question from a previous screen. The second column allows the user to select an operator applicable to the type of question asked. The third column allows the user to enter one or more values depending on the selected operator. Object Model public enum Operations { ... } public class Condition { int QuestionId { get; set; } Operations Operation { get; set; } List<object> Parameters { get; private set; } } List<Condition> pageSkipConditions; Controller Logic bool allConditionsTrue = pageSkipConditions.Count > 0; foreach (Condition c in pageSkipConditions) { allConditionsTrue &= Evaluate(previousAnswers, c); } // ... private bool Evaluate(List<Answers> previousAnswers, Condition c) { switch (c.Operation) { case Operations.StartsWith: // logic for this operation // etc. } }

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  • Which parallel pattern to use?

    - by Wim Van Houts
    I need to write a server application that fetches mails from different mail servers/mailboxes and then needs to process/analyze these mails. Traditionally, I would do this multi-threaded, launching a thread for fetching mails (or maybe one per mailbox) and then process the mails. We are moving more and more to servers where we have 8+ cores, so I would like to make use of these cores as much as possible (and not use 1 at 100% and leave the seven others untouched). So conceptually, as an example, it would be nice that I could write the application in such a way that two cores are "continuously" fetching emails and four cores are "continuously" processing/analyzing the emails (since processing and analyzing mails is more CPU intensive than fetching mails). This seems like a good concept, but after studying some parallel patterns, I'm not really sure how this is best implemented. None of the patterns really fit. I'm working in VS2012, native C++, but I guess from a design point of view this does not really matter and just some pointers on how to organize this would be great!

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  • Extension objects pattern

    - by voroninp
    In this MSDN Magazine article Peter Vogel describes Extension Objects partten. What is not clear is whether extensions can be later implemented by client code residing in a separate assembly. And if so how in this case can extension get acces to private members of the objet being extended? I quite often need to set different access levels for different classes. Sometimes I really need that descendants does not have access to the mebmer but separate class does. (good old friend classes) Now I solve this in C# by exposing callback properties in interface of the external class and setting them with private methods. This also alows to adjust access: read only or read|write depending on the desired interface. class Parent { private int foo; public void AcceptExternal(IFoo external) { external.GetFooCallback = () => this.foo; } } interface IFoo { Func<int> GetFooCallback {get;set;} } Other way is to explicitly implement particular interface. But I suspect more aspproaches exist.

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  • MVC pattern synchronisation

    - by Hariprasad
    I am facing a problem in synchronizing my model and view threads I have a view which is table. In it, user can select a few rows. I update the view as soon as the user clicks on any row since I don't want the UI to be slow. This updating is done by a logic which runs in the controller thread below. At the same time, the controller will update the model data too, which takes place in a different thread. i.e., controller puts the query in a queue, which is then executed by the model thread - which is a single-threaded interface. As soon as the query executes, controller will get a signal. Now, In order to keep the view and model synchronized, I will update the view again based on the return value of the query (the data returned by model) - even though I updated the view already for that user action. But, I am facing issues because, its taking a lot of time for the model to return the result, by that time user would have performed multiple clicks. So, as a result of updating the view again based on the information from model, the view sometimes goes back to the state in which the previous clicks were made (Suppose user clicks thrice on different rows. I update the view as soon as the click happens. Also, I update the view when I get data back from the model - which is supposed to be same as the already updated state of the view. Now, when the user clicks third time, I get data for the first click from model. As a result, view goes back to a state which is generated by the first click) Is there any way to handle such a synchronization issue?

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  • Choosing the right Design Pattern

    - by Carl Sagan
    I've always recognized the importance of utilizing design patterns. I'm curious as to how other developers go about choosing the most appropriate one. Do you use a series of characteristics (like a flowchart) to help you decide? For example: If objects are related, but we do not want to specify concrete class, consider Abstract When instantiation is left to derived classes, consider Factory Need to access elements of an aggregate object sequentially, try Iterator or something similar?

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  • while(true) and loop-breaking - anti-pattern?

    - by KeithS
    Consider the following code: public void doSomething(int input) { while(true) { TransformInSomeWay(input); if(ProcessingComplete(input)) break; DoSomethingElseTo(input); } } Assume that this process involves a finite but input-dependent number of steps; the loop is designed to terminate on its own as a result of the algorithm, and is not designed to run indefinitely (until cancelled by an outside event). Because the test to see if the loop should end is in the middle of a logical set of steps, the while loop itself currently doesn't check anything meaningful; the check is instead performed at the "proper" place within the conceptual algorithm. I was told that this is bad code, because it is more bug-prone due to the ending condition not being checked by the loop structure. It's more difficult to figure out how you'd exit the loop, and could invite bugs as the breaking condition might be bypassed or omitted accidentally given future changes. Now, the code could be structured as follows: public void doSomething(int input) { TransformInSomeWay(input); while(!ProcessingComplete(input)) { DoSomethingElseTo(input); TransformInSomeWay(input); } } However, this duplicates a call to a method in code, violating DRY; if TransformInSomeWay were later replaced with some other method, both calls would have to be found and changed (and the fact that there are two may be less obvious in a more complex piece of code). You could also write it like: public void doSomething(int input) { var complete = false; while(!complete) { TransformInSomeWay(input); complete = ProcessingComplete(input); if(!complete) { DoSomethingElseTo(input); } } } ... but you now have a variable whose only purpose is to shift the condition-checking to the loop structure, and also has to be checked multiple times to provide the same behavior as the original logic. For my part, I say that given the algorithm this code implements in the real world, the original code is the most readable. If you were going through it yourself, this is the way you'd think about it, and so it would be intuitive to people familiar with the algorithm. So, which is "better"? is it better to give the responsibility of condition checking to the while loop by structuring the logic around the loop? Or is it better to structure the logic in a "natural" way as indicated by requirements or a conceptual description of the algorithm, even though that may mean bypassing the loop's built-in capabilities?

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  • Visitor-pattern vs inheritance for rendering

    - by akaltar
    I have a game engine that currently uses inheritance to provide a generic interface to do rendering: class renderable { public: void render(); }; Each class calls the gl_* functions itself, this makes the code hard to optimize and hard to implement something like setting the quality of rendering: class sphere : public renderable { public: void render() { glDrawElements(...); } }; I was thinking about implementing a system where I would create a Renderer class that would render my objects: class sphere { void render( renderer* r ) { r->renderme( *this ); } }; class renderer { renderme( sphere& sphere ) { // magically get render resources here // magically render a sphere here } }; My main problem is where should I store the VBOs and where should I Create them when using this method? Should I even use this approach or stick to the current one, perhaps something else? PS: I already asked this question on SO but got no proper answers.

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  • How to Do htaccess 301 Redirect from Old Filename Pattern to New Filename Pattern?

    - by user249493
    I have a bunch of old files prefixed with "old-" (e.g. "old-abcde.php"). I need an htaccess rule to set up a 301 redirect so that any request for a file starting with "old-" goes to its corresponding new version (e.g. "abcde.php"). To be clear, I have many files, not just one, so I can't do a literal filename match. I basically just need to strip off the "old-" from request and redirect to the version without it. I know I probably just need a simple regular expression, but I'm not good at writing them. Can anyone provide assistance?

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  • PC always boots into Command Line

    - by Neptun1337
    My current Problem is, that when I try to install Ubuntu 12.04 Desktop, neither unity nor gnome are installed. During the installation, I am prompted with the message that only the core is installed, and which additional packages I would like to have installed. When I select ubuntu-desktop, the installer grabs some packages and installs them, but after completing the installation and booting into my Ubuntu, i dont get any GUI, but instead I have the command line interface. When I try to start a new Unity session, i get an error saying that Unity is not installed, so I tried to install it. However this changes nothing, my PC still boots into the Command Line. Are there any solutions to my problem? Any help would be greatly appreciated. Thanks in advance. EDIT: I tried to fix it with the following commands: $ sudo apt-get install ubuntu-desktop $ sudo apt-get install gdm $ sudo /etc/init.d/gdm start When I try to boot, I get the Ubuntu splash screen, but then the screen mainly shows white squares, with a few black ones at the top.

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  • Dynamic Strategy Pattern [migrated]

    - by Karl Barker
    So I'm writing a web service architecture which includes FunctionProvider classes which do the actual processing of requests, and a main Endpoint class which receives and delegates requests to the proper FunctionProvider. I don't know exactly the FunctionProviders available at runtime, so I need to be able to 'register' (if that's the right word) them with my main Endpoint class, and query them to see if they match an incoming request. public class MyFunc implements FunctionProvider{ static { MyEndpoint.register(MyFunc); } public Boolean matchesRequest(Request req){...} public void processRequest(Request req){...} } public class MyEndpoint{ private static ArrayList<FunctionProvider> functions = new ArrayList<FunctionProvider>(); public void register(Class clz){ functions.add(clz); } public void doPost(Request request){ //find the FunctionProvider in functions //matching the request } } I've really not done much reflective Java like this (and the above is likely wrong, but hopefully demonstrates my intentions). What's the nicest way to implement this without getting hacky?

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  • Pattern for loading and handling resources

    - by Enoon
    Many times there is the need to load external resources into the program, may they be graphics, audio samples or text strings. Is there a patten for handling the loading and the handling of such resources? For example: should I have a class that loads all the data and then call it everytime I need the data? As in: GraphicsHandler.instance().loadAllData() ...//and then later: draw(x,y, GraphicsHandler.instance().getData(WATER_IMAGE)) //or maybe draw(x,y, GraphicsHandler.instance().WATER_IMAGE) Or should I assign each resource to the class where it belongs? As in (for example, in a game): Graphics g = GraphicsLoader.load(CHAR01); Character c = new Character(..., g); ... c.draw(); Generally speaking which of these two is the more robust solution? GraphicsHandler.instance().getData(WATER_IMAGE) //or GraphicsHandler.instance().WATER_IMAGE //a constant reference

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  • Layering Design Pattern in Java clean code style

    - by zeraDev
    As a Java developer, I am developing trying to use the clean code rules. But in my team we are facing a concrete problem: We have a business layer offering a service called "createObject", this service makes a lot of operation which can result to problem. E.g: parentObjectDontExist, objectAlreadyExist, dontHaveAuthorizationToCreate, operationFailed... and we want the UI using this service to display different information messages depending which error occurred. In old java dev, we should have create all signed exception type and throw it in createObject. As Clean code says, it is forbidden to use Exception for business logic AND signed exceptions are evil... Why not...But i don't know how to solved this problem and i don't want to use return code. How do you do? Thanks for youre experience return.

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  • Entity and pattern validation vs DB constraint

    - by Joerg
    When it comes to performance: What is the better way to validate the user input? If you think about a phone number and you only want numbers in the database, but it could begin with a 0, so you will use varchar: Is it better to check it via the entity model like this: @Size(min = 10, max = 12) @Digits(fraction = 0, integer = 12) @Column(name = "phone_number") private String phoneNumber; Or is it better to use on the database side a CHECK (and no checking in the entity model) for the same feature?

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  • MVC Design Pattern to Combine Multiple Models for use

    - by roverred
    In my design, I have multiple models and each model has a controller. I need to use all the models to process some operation. Most examples I see are pretty simple with 1 view, 1 controller, and 1 model. How would you get all these models together? Only ways I can think of are 1) Have a top-level controller which has a reference to every controller. Those controllers will have a getter/setter function for their model. Does this violate MVC because every controller should have a model? 2) Have an Intermediate class to combine every model into a one model. Then you create a controller for that new super model. Do you know of any better ideas? Thanks.

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  • "Collection Wrapper" pattern - is this common?

    - by Prog
    A different question of mine had to do with encapsulating member data structures inside classes. In order to understand this question better please read that question and look at the approach discussed. One of the guys who answered that question said that the approach is good, but if I understood him correctly - he said that there should be a class existing just for the purpose of wrapping the collection, instead of an ordinary class offering a number of public methods just to access the member collection. For example, instead of this: class SomeClass{ // downright exposing the concrete collection. Things[] someCollection; // other stuff omitted Thing[] getCollection(){return someCollection;} } Or this: class SomeClass{ // encapsulating the collection, but inflating the class' public interface. Thing[] someCollection; // class functionality omitted. public Thing getThing(int index){ return someCollection[index]; } public int getSize(){ return someCollection.length; } public void setThing(int index, Thing thing){ someCollection[index] = thing; } public void removeThing(int index){ someCollection[index] = null; } } We'll have this: // encapsulating the collection - in a different class, dedicated to this. class SomeClass{ CollectionWrapper someCollection; CollectionWrapper getCollection(){return someCollection;} } class CollectionWrapper{ Thing[] someCollection; public Thing getThing(int index){ return someCollection[index]; } public int getSize(){ return someCollection.length; } public void setThing(int index, Thing thing){ someCollection[index] = thing; } public void removeThing(int index){ someCollection[index] = null; } } This way, the inner data structure in SomeClass can change without affecting client code, and without forcing SomeClass to offer a lot of public methods just to access the inner collection. CollectionWrapper does this instead. E.g. if the collection changes from an array to a List, the internal implementation of CollectionWrapper changes, but client code stays the same. Also, the CollectionWrapper can hide certain things from the client code - from example, it can disallow mutation to the collection by not having the methods setThing and removeThing. This approach to decoupling client code from the concrete data structure seems IMHO pretty good. Is this approach common? What are it's downfalls? Is this used in practice?

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  • Ubuntu Server 12 not spawning a serial ttyS0 when running on Xen

    - by segfaultreloaded
    I have this problem on more than one host, so the specific hardware is not an issue. Bare metal Ubuntu 12 is not creating a login process on the only serial port, in the default configuration. The serial port works correctly with the firmware. It works correctly with Grub2. I have even connected the serial line to 2 different external client boxes, so the problem is neither the hardware nor the remote client. When finally booted, the system fails to create the login process. root@xenpro3:~# ps ax | grep tty 1229 tty4 Ss+ 0:00 /sbin/getty -8 38400 tty4 1233 tty5 Ss+ 0:00 /sbin/getty -8 38400 tty5 1239 tty2 Ss+ 0:00 /sbin/getty -8 38400 tty2 1241 tty3 Ss+ 0:00 /sbin/getty -8 38400 tty3 1245 tty6 Ss+ 0:00 /sbin/getty -8 38400 tty6 1403 tty1 Ss+ 0:00 /sbin/getty -8 38400 tty1 1996 pts/0 S+ 0:00 grep --color=auto tty root@xenpro3:~# dmesg | grep tty [ 0.000000] Command line: BOOT_IMAGE=/vmlinuz-3.2.0-30-generic root=/dev/mapper/xenpro3-root ro console=ttyS0,115200n8 [ 0.000000] Kernel command line: BOOT_IMAGE=/vmlinuz-3.2.0-30-generic root=/dev/mapper/xenpro3-root ro console=ttyS0,115200n8 [ 0.000000] console [ttyS0] enabled [ 2.160986] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A [ 2.203396] serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A [ 2.263296] 00:08: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A [ 2.323102] 00:09: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A root@xenpro3:~# uname -a Linux xenpro3 3.2.0-30-generic #48-Ubuntu SMP Fri Aug 24 16:52:48 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux root@xenpro3:~# I have tried putting a ttyS0.conf file in /etc/initab, which solves the problem bare metal but I still cannot get the serial port to work when booting Ubuntu on top of Xen, as domain 0. My serial line output looks like this, when booting Xen /dev/ttyS0 at 0x03f8 (irq = 4) is a 16550A * Exporting directories for NFS kernel daemon... [ OK ] * Starting NFS kernel daemon [ OK ] SSL tunnels disabled, see /etc/default/stunnel4 [ 18.654627] XENBUS: Unable to read cpu state [ 18.659631] XENBUS: Unable to read cpu state [ 18.664398] XENBUS: Unable to read cpu state [ 18.669248] XENBUS: Unable to read cpu state * Starting Xen daemons [ OK ] mountall: Disconnected from Plymouth At this point, the serial line is no longer connected to a process. Xen itself is running just fine. Dmesg gives me a long list of [ 120.236841] init: ttyS0 main process ended, respawning [ 120.239717] ttyS0: LSR safety check engaged! [ 130.240265] init: ttyS0 main process (1631) terminated with status 1 [ 130.240294] init: ttyS0 main process ended, respawning [ 130.242970] ttyS0: LSR safety check engaged! which is no surprise because I see root@xenpro3:~# ls -l /dev/ttyS? crw-rw---- 1 root tty 4, 64 Nov 7 14:04 /dev/ttyS0 crw-rw---- 1 root dialout 4, 65 Nov 7 14:04 /dev/ttyS1 crw-rw---- 1 root dialout 4, 66 Nov 7 14:04 /dev/ttyS2 crw-rw---- 1 root dialout 4, 67 Nov 7 14:04 /dev/ttyS3 crw-rw---- 1 root dialout 4, 68 Nov 7 14:04 /dev/ttyS4 crw-rw---- 1 root dialout 4, 69 Nov 7 14:04 /dev/ttyS5 crw-rw---- 1 root dialout 4, 70 Nov 7 14:04 /dev/ttyS6 crw-rw---- 1 root dialout 4, 71 Nov 7 14:04 /dev/ttyS7 crw-rw---- 1 root dialout 4, 72 Nov 7 14:04 /dev/ttyS8 crw-rw---- 1 root dialout 4, 73 Nov 7 14:04 /dev/ttyS9 If I manually change the group of /dev/ttyS0 to dialout, it gets changed back. I have made no changes to the default udev rules, so I cannot see where this problem is coming from. Sincerely, John

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  • Designing web-based plugin systems correctly so they don't waste as many resources?

    - by Xeoncross
    Many CMS systems which rely on third parties for much of their code often build "plugin" or "hooks" systems to make it easy for developers to modify the codebase's actions without editing the core files. This usually means an Observer or Event design pattern. However, when you look at systems like wordpress you see that on every page they load some kind of bootstrap file from each of the plugin's folders to see if that plugin will need to run that request. Its this poor design that causes systems like wordpress to spend many extra MB's of memory loading and parsing unneeded items each page. Are there alternative ways to do this? I'm looking for ideas in building my own. For example, Is there a way to load all this once and then cache the results so that your system knows how to lazy-load plugins? In other words, the system loads a configuration file that specifies all the events that plugin wishes to tie into and then saves it for future requests? If that also performs poorly, then perhaps there is a special file-structure that could be used to make educated guesses about when certain plugins are unneeded to fullfil the request. Any ideas? If anyone wants an example of the "plugin" concept you can find one here.

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