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  • A design pattern for data binding an object (with subclasses) to asp.net user control

    - by Rohith Nair
    I have an abstract class called Address and I am deriving three classes ; HomeAddress, Work Address, NextOfKin address. My idea is to bind this to a usercontrol and based on the type of Address it should bind properly to the ASP.NET user control. My idea is the user control doesn't know which address it is going to present and based on the type it will parse accordingly. How can I design such a setup, based on the fact that, the user control can take any type of address and bind accordingly. I know of one method like :- Declare class objects for all the three types (Home,Work,NextOfKin). Declare an enum to hold these types and based on the type of this enum passed to user control, instantiate the appropriate object based on setter injection. As a part of my generic design, I just created a class structure like this :- I know I am missing a lot of pieces in design. Can anybody give me an idea of how to approach this in proper way.

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  • MVC Pattern, ViewModels, Location of conversion.

    - by Pino
    I've been working with ASP.Net MVC for around a year now and have created my applications in the following way. X.Web - MVC Application Contains Controller and Views X.Lib - Contains Data Access, Repositories and Services. This allows us to drop the .Lib into any application that requires it. At the moment we are using Entity Framework, the conversion from EntityO to a more specific model is done in the controller. This set-up means if a service method returns an EntityO and then the Controller will do a conversion before the data is passed to a view. I'm interested to know if I should move the conversion to the Service so that the app doesn't have Entity Objects being passed around.

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  • Bayes Misclassification error and plot : pattern recognition [closed]

    - by user1214586
    Below is a Matlab code for Bayes classifier which classifies arbitrary numbers into their classes. training = [3;5;17;19;24;27;31;38;45;48;52;56;66;69;73;78;84;88]; target_class = [0;0;10;10;20;20;30;30;40;40;50;50;60;60;70;70;80;80]; test = [1:2:90]'; class = classify(test,training, target_class, 'diaglinear'); % Naive Bayes classifier [test class] If someone could provide code snippets for calculating the Bayes error for misclassification and accuracy.Also, is it possible to plot a scatter plot and histogram indicating the number of data points belonging to different classes? Thank you.

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  • Transient VO : Powerful J2EE Design Pattern

    - by Vijay Mohan
    We had a use-case wherein, the communication has to happen between regions residing under differenet taskfows. Essentially, they had a common set of parameters to be used. Initially, we resorted to the  use of pageFlowScope variables, but they are tightly coupled with the individual task flows. So, how the communication has to happen..?Some of the alternatives that we brainstormed into are - 1.usage of adf contextual event - This is a powerful feature indeed for such use-cases, but there is a considerable cost involved with it. So, before resorting to it, you have to make sure that you have good enough reason to use it.It actually does a server roundtrip and also the issue of an event and listening part to it is also something which requires your attention !!2.Use a transientVO with shared data control scope - with shared data control scope, the transient VO rows would be persistent across the task flows in your application. All you have to do is to create the attributes in the transientVO(prefereably with the same names - for the ease of conversion) and create some utility methods in VOImpl for creating row, updating row and deleting a row. You also have to make sure that the vo row is initialized per http request( this you can do in a bookmark method of your index.jspx - residing in adfc-config.xml), else the ui fields binded to the transient vo attributes won't render in UI.Hope, this helps and this should be a common use-case across apps.

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  • Implementing MVC pattern in SWT application

    - by Pradeep Simha
    I am developing an SWT application (it's basically an Eclipse plugin, so I need to use SWT). Currently my design is as follows: Model: In model, I have POJOs which represents the actual fields in views. View: It is a dumb layer, it contains just UI and contains no logic (not even event handlers) Controller: It acts as a mediator b/w those two layers. Also it is responsible for creating view layer, handling events etc. Basically I have created all of the controls in view as a static like this public static Button btnLogin and in controller I have a code like this: public void createLoginView(Composite comp) { LoginFormView.createView(comp); //This createView method is in view layer ie LoginFormView LoginFormView.btnLogin.addSelectionListener(new SelectionListener() { //Code goes here }); } Similalrly I have done for other views and controls. So that in main class and other classes I am calling just createLoginView of controller. I am doing similar thing for other views. So my question, is what I am doing is correct? Is this design good? Or I should have followed any other approach. Since I am new to SWT and Eclipse plugin development (basically I am Java EE developer having 4+ years of exp). Any tips/pointers would be appreciated.

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  • Make a controller a superclass in MVC design pattern

    - by Nikola
    I am really confused how to handle this. I have: model.Outsider model.SubContractor (which extends Outsider) Basically, Outsider would mean Supplier, but SubContractor is not a Supplier itself so I had to divide it somehow. I used to have model.Outsider (super class of the two bellow) model.Supplier model.SubContractor But Supplier didn't have any unique fields so I have removed it (Was this correct?) So, continuing, I have db layer which has: db.DBOutsider db.DBSubContractor (which again extends the top one) And I have no place to put my Supplier methods. I can do that in DBOutsider, but then DBSubContractor (which extends DBOutsider) would get unnecessary methods. Do I create a DBSupplier even though there is no such class in the model layer? Then again, going to controller layer. It is the same situation as db layer. I have OutsiderController and SubContractorController (which extends the first one) (is this correct in first place? to have an extended controller?). But I have no place to put the methods which are concerned with Supplier and if I put them in the OutsiderController the SubContractorController would recieve unneccessary methods. At the moment I am going for the extra DBSupplier and SupplierController classes, but I have no idea if this is the correct way. Basically what perplexes me is the "empty" Supplier. Since it is supposed to be an Outsider but has no extra methods or fields, should there be an empty class?

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  • Scala factory pattern returns unusable abstract type

    - by GGGforce
    Please let me know how to make the following bit of code work as intended. The problem is that the Scala compiler doesn't understand that my factory is returning a concrete class, so my object can't be used later. Can TypeTags or type parameters help? Or do I need to refactor the code some other way? I'm (obviously) new to Scala. trait Animal trait DomesticatedAnimal extends Animal trait Pet extends DomesticatedAnimal {var name: String = _} class Wolf extends Animal class Cow extends DomesticatedAnimal class Dog extends Pet object Animal { def apply(aType: String) = { aType match { case "wolf" => new Wolf case "cow" => new Cow case "dog" => new Dog } } } def name(a: Pet, name: String) { a.name = name println(a +"'s name is: " + a.name) } val d = Animal("dog") name(d, "fred") The last line of code fails because the compiler thinks d is an Animal, not a Dog.

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  • Choice the project pattern, advice for this case

    - by Lucas Rodrigues Sena
    I have a project in MVC4 entity framework, and have to adapt it to possible updates on the dlls and system do not stop work. I'm using portable Areas, but have difficulty creating 5 modules and about 5 functionality for each modules with fully functioning independently as a dll and database. 1- Reflection DLLs, the system works "on the fly". (I cant do it on mvc4 at moment). 2- Portables Areas (I need to do one area for each modules*functionality 5*5 Areas). Confuse way and I'm afraid if this is ridiculous. 3- Implement WFC on MVC4, compatible? 4- Other better way?

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  • Architecture/pattern resources for small applications and tools

    - by s73v3r
    I was wondering if anyone had any resources or advice related to using architecture patterns like MVVM/MVC/MVP/etc on small applications and tools, as opposed to large, enterprisy ones. EDIT: Most of the information I see on application architecture is directed at large, enterprise applications. I'm just writing small programs and tools. As far as using these architecture patterns, is it generally worthwhile to go through the overhead of using an MVC/MVVM framework? Or would I be better off keeping it simple?

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  • Design pattern for an ASP.NET project using Entity Framework

    - by MPelletier
    I'm building a website in ASP.NET (Web Forms) on top of an engine with business rules (which basically resides in a separate DLL), connected to a database mapped with Entity Framework (in a 3rd, separate project). I designed the Engine first, which has an Entity Framework context, and then went on to work on the website, which presents various reports. I believe I made a terrible design mistake in that the website has its own context (which sounded normal at first). I present this mockup of the engine and a report page's code behind: Engine (in separate DLL): public Engine { DatabaseEntities _engineContext; public Engine() { // Connection string and procedure managed in DB layer _engineContext = DatabaseEntities.Connect(); } public ChangeSomeEntity(SomeEntity someEntity, int newValue) { //Suppose there's some validation too, non trivial stuff SomeEntity.Value = newValue; _engineContext.SaveChanges(); } } And report: public partial class MyReport : Page { Engine _engine; DatabaseEntities _webpageContext; public MyReport() { _engine = new Engine(); _databaseContext = DatabaseEntities.Connect(); } public void ChangeSomeEntityButton_Clicked(object sender, EventArgs e) { SomeEntity someEntity; //Wrong way: //Get the entity from the webpage context someEntity = _webpageContext.SomeEntities.Single(s => s.Id == SomeEntityId); //Send the entity from _webpageContext to the engine _engine.ChangeSomeEntity(someEntity, SomeEntityNewValue); // <- oops, conflict of context //Right(?) way: //Get the entity from the engine context someEntity = _engine.GetSomeEntity(SomeEntityId); //undefined above //Send the entity from the engine's context to the engine _engine.ChangeSomeEntity(someEntity, SomeEntityNewValue); // <- oops, conflict of context } } Because the webpage has its own context, giving the Engine an entity from a different context will cause an error. I happen to know not to do that, to only give the Engine entities from its own context. But this is a very error-prone design. I see the error of my ways now. I just don't know the right path. I'm considering: Creating the connection in the Engine and passing it off to the webpage. Always instantiate an Engine, make its context accessible from a property, sharing it. Possible problems: other conflicts? Slow? Concurrency issues if I want to expand to AJAX? Creating the connection from the webpage and passing it off to the Engine (I believe that's dependency injection?) Only talking through ID's. Creates redundancy, not always practical, sounds archaic. But at the same time, I already recuperate stuff from the page as ID's that I need to fetch anyways. What would be best compromise here for safety, ease-of-use and understanding, stability, and speed?

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  • Design pattern for client/server sessions?

    - by nonot1
    Are there any common patterns or general guidance I can learn from for how to design a client/server system where the both the client and server must maintain some kind per-client session state? I've found any number of libraries that can help with some of the plumbing, but it's the overall design I'm wondering about. Open issues in my mind: How to structure the client/server communication so that bidirectional synchronous and asynchronous requests are possible? The server side needs to spawn a couple of per-connected-client session-long helper process. How to manage that? How to manage the mapping from a given client (and any of it's requests) to server state and helper process instances in the face of multiple clients and intermittent network connectivity. Most communication can be simple blocking request/reply, but some will be long running processing tasks that the client will want to keep tabs on. To the extent that it matters, the platform is Linux/C/C++. Not web based. Just an existing thick-client software app being modified to talk to backend servers for some tasks.

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  • Liskov substitution and abstract classes / strategy pattern

    - by Kolyunya
    I'm trying to follow LSP in practical programming. And I wonder if different constructors of subclasses violate it. It would be great to hear an explanation instead of just yes/no. Thanks much! P.S. If the answer is no, how do I make different strategies with different input without violating LSP? class IStrategy { public: virtual void use() = 0; }; class FooStrategy : public IStrategy { public: FooStrategy(A a, B b) { c = /* some operations with a, b */ } virtual void use() { std::cout << c; } private: C c; }; class BarStrategy : public IStrategy { public: BarStrategy(D d, E e) { f = /* some operations with d, e */ } virtual void use() { std::cout << f; } private: F f; };

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  • Help to understand the abstract factory pattern

    - by Chobeat
    I'm learning the 23 design patterns of the GoF. I think I've found a way to understand and simplify how the Abstract Factory works but I would like to know if this is a correct assumption or if I am wrong. What I want to know is if we can see the result of the Abstract Factory method as a matrix of possible products where there's a Product for every "Concrete Factory" x "AbstractProduct" where the Concrete Factory is a single implementation among the implementations of an AbstractFactory and an AbstractProduct is an interface among the interfaces to create Products. Is this correct or am I missing something?

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  • Design pattern and best practices

    - by insane-36
    I am an iphone developer. I am quite confident on developing iphone application with some minimal feature. I would consider myself as a fair application developer but the code I write is not so much structured. I make vey little use of MVC because I dont seem to find places to impose MVC. Most of the time, I create application with viewcontrollers and very few models only. How could I improve the skill for making my code more reusable, standard, easy and maintainable. I have seen few books on design patterns and tried few chapters myself but I dont seem to skip my habit. I know few of them but I am not being able to apply those patterns into my app. What is the best way to learn the design patterns and coding habit. Any kind of suggestion is warmly welcomed.

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  • The Singleton Pattern

    - by Darren Young
    Hi, I am a new programmer (4 months into my first job) and have recently taken an interest in design patterns. One that I have used recently is the Singleton. However, looking at some comments on this thread Overused or abused programming techniques .......it has some bad feedback. Come somebody explain why? I have found it useful in some places, however I could probably have achieved the same without it using a static class. Thanks.

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  • State Design Pattern .NET Code Sample

    using System;using System.Collections.Generic;using System.Linq;using System.Text;class Program{ static void Main(string[] args) { Person p1 = new Person("P1"); Person p2 = new Person("P2"); p1.EatFood(); p2.EatFood(); p1.Vomit(); p2.Vomit(); }}interface StomachState{ void Eat(Person p); void Vomit(Person p);}class StomachFull : StomachState{ public void Eat(Person p) { Console.WriteLine("Can't eat more."); } public void Vomit(Person p) { Console.WriteLine("I've just Vomited."); p.StomachState = new StomachEmpty(); }}class StomachEmpty : StomachState{ public void Eat(Person p) { Console.WriteLine("I've just had food."); p.StomachState = new StomachFull(); } public void Vomit(Person p) { Console.WriteLine("Nothing to Vomit."); }}class Person{ private StomachState stomachState; private String personName; public Person(String personName) { this.personName = personName; StomachState = new StomachEmpty(); } public StomachState StomachState { get { return stomachState; } set { stomachState = value; Console.WriteLine(personName + " Stomach State Changed to " + StomachState.GetType().Name); Console.WriteLine("***********************************************\n"); } } public Person(StomachState StomachState) { this.StomachState = StomachState; } public void EatFood() { StomachState.Eat(this); } public void Vomit() { StomachState.Vomit(this); }} span.fullpost {display:none;}

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  • Using a front controller design pattern doesn't allow images to be served

    - by MrMe TumbsUp
    I am currently using a front controller. All requests for my website go through it. I have a problem with image links like: <img src="img/image.jpg" /> Then my front controller will try to dispatch the request to: application/controller/ImgController.php. Then the image won't load. I think it has something to do with the .htaccess file: RewriteEngine On RewriteCond %{REQUEST_FILENAME} -s [OR] RewriteCond %{REQUEST_FILENAME} -l [OR] RewriteCond %{REQUEST_FILENAME} -d RewriteRule ^.*$ - [NC,L] RewriteRule ^.*$ index.php [NC,L]

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  • Is ORM an Anti-Pattern?

    - by derphil
    I had a very stimulating and interessting discussion with a colleague about ORM and it's Pros and Cons. In my opinion, an ORM is useful only in the rarest cases. At least in my experience. But I don't want to list my own arguments at this time. So I ask you, what do you think about ORM? What are the Pros and the Cons? P.S. I've posted this "question" yesterday on Stackoverflow, but some of the user think, that this should better posted here.

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  • Video game "Gish" will only launch from command line

    - by aberration
    Platform: Lubuntu 11.10 x64 Program: Gish When I try to launch Gish from the command line (/opt/gish/gi.sh), there are no problems. But when I try to launch it from the LXDE menu, it will not start. Contents of /usr/share/applications/gish.desktop: [Desktop Entry] Categories=Game;ActionGame;AdventureGame;ArcadeGame; Exec=/opt/gish/gi.sh Path=/opt/gish Icon=x-gish Terminal=false Type=Application Name=Gish I tried changing Terminal=false to Terminal=true to debug it, but then I just got a blank terminal, and the game didn't start. Edit: Here is some additional information, as requested by Eliah Kagan below: I tried editing /usr/share/applications/gish.desktop, as recommended, but it had no effect However, ~/.xsession-errors contained the following error: [: 8: x86_64: unexpected operator ./gish_32: error while loading shared libraries: libGL.so.1: wrong ELF class: ELFCLASS64 I think there's a problem with the /opt/gish/gi.sh shell script. This is its contents: cd /opt/gish/ MACHINE_TYPE=`uname -m` if [ ${MACHINE_TYPE} == 'x86_64' ]; then ./gish_64 else ./gish_32 fi I'm not too familiar with Bash, so hopefully someone else can point out the error. I have a 64-bit machine. I think that when the script is run from the command line, it's properly launching the 64-bit version (/opt/gish/gish_64), but when it's run from the LXDE menu, it's launching the 32-bit version (/opt/gish/gish_32), which is causing the libGL.so.1 error. However, this may be related to my libGL.so.1 problems with 2 other games.

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  • Masking OpenGL texture by a pattern

    - by user1304844
    Tiled terrain. User wants to build a structure. He presses build and for each tile there is an "allow" or "disallow" tile sprite added to the scene. FPS drops right away, since there are 600+ tiles added to the screen. Since map equals screen, there is no scrolling. I came to an idea to make an allow grid covering the whole map and mask the disallow fields. Approach 1: Create allow and disallow grid textures. Draw a polygon on screen. Pass both textures to the fragment shader. Determine the position inside the polygon and use color from allowTexture if the fragment belongs to the allow field, disallow otherwise Problem: How do I know if I'm on the field that isn't allowed if I cannot pass the matrix representing the map (enum FieldStatus[][] (Allow / Disallow)) to the shader? Therefore, inside the shader I don't know which fragments should be masked. Approach 2: Create allow texture. Create an empty texture buffer same size as the allow texture Memset the pixels of the empty texture to desired color for each pixel that doesn't allow building. Draw a polygon on screen. Pass both textures to the fragment shader. Use texture2 color if alpha 0, texture1 color otherwise. Problem: I'm not sure what is the right way to manipulate pixels on a texture. Do I just make a buffer with width*height*4 size and memcpy the color[] to desired coordinates or is there anything else to it? Would I have to call glTexImage2D after every change to the texture? Another problem with this approach is that it takes a lot more work to get a prettier effect since I'm manipulating the color pixels instead of just masking two textures. varying vec2 TexCoordOut; uniform sampler2D Texture1; uniform sampler2D Texture2; void main(void){ vec4 allowColor = texture2D(Texture1, TexCoordOut); vec4 disallowColor = texture2D(Texture2, TexCoordOut); if(disallowColor.a > 0){ gl_FragColor= disallowColor; }else{ gl_FragColor= allowColor; }} I'm working with OpenGL on Windows. Any other suggestion is welcome.

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  • Authorization design-pattern / practice?

    - by Lawtonfogle
    On one end, you have users. On the other end, you have activities. I was wondering if there is a best practice to relate the two. The simplest way I can think of is to have every activity have a role, and assign every user every role they need. The problem is that this gets really messy in practice as soon as you go beyond a trivial system. A way I recently designed was to have users who have roles, and roles have privileges, and activities require some combinations of privileges. For the trivial case, this is more complex, but I think it will scale better. But after I implemented it, I felt like it was overkill for the system I had. Another option would be to have users, who have roles, and activities require you to have a certain role to perform with many activities sharing roles. A more complex variant of this would given activities many possible roles, which you only needed one of. And an even more complex variant would be to allow logical statements of role ownership to use an activity (i.e. Must have A and (B exclusive or C) and must not have D). I could continue to list more, but I think this already gives a picture. And many of these have trade offs. But in software design, there are oftentimes solutions, while perhaps not perfect in every possible case, are clearly top of the pack to an extent it isn't even considered opinion based (i.e. how to store passwords, plain text is worse, hashing better, hashing and salt even better, despite the increased complexity of each level) (i.e. 2, Smart UI designs for applications are bad, even if it is subjective as to what the best design is). So, is there a best practice for authorization design that is not purely opinion based/subjective?

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  • bash-like features in sqlplus, rman and other Oracle command line tools

    - by Gilles Haro
    As far as I can remember, I have always been complaining about the lack of “recall last command” from within sqlplus. Such a basic thing, available in any bash shell or windows cmd terminal, remains missing with Oracle command lines tools. Thanks to davidw who published a post in the french blog EASYTEAM, it is now possible to use a simple rpm package rlwrap to enhance sqlplus, dgmgrl, rman, … tools and give them bash “recall/completion” capabilities. I installed it in a few minutes and I am already wondering how can people work without it. The steps are here : Get the rpm file from sites like RPM PBone. AS root, install the package rpm -ivh rlwrap-0.37-1.el5.x86_64.rpm As Oracle, create a dictionnary file (for autocompletion) . This file is made of a series of words to be used for autocompletion. Put in it the list of dictionary tables, the list of sql commands, the list of sqlplus commands… whatever your like. And use the <tab> key as you would in a bash shell. $HOME/.oracle_keywords Create an alias for sqlplus alias sqlplus='/usr/bin/rlwrap -if $HOME/.oracle_keywords $ORACLE_HOME/bin/sqlplus' And enjoy it !!! Thank you DavidW. Gilles Haro Technical Expert - Core Technology, Oracle Consulting  Technorati Tags: rlwrap bash sqlplus

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  • Algorithmic Forecasting and Pattern Recognition

    - by Ryan King
    Say a user could enter project data into my software. Each project has 2 variables "size" and "work" and they're related but the relationship is not known. Is there a way to programmatically determine the relationship between the variables based on previous data and forecast the amount of work provided if only given the size of the project in the future? For Example, say the user had manually entered the following projects. Project 1 - Size:1, Work: 4 Project 2 - Size:2, Work: 7 Project 3 - Size:3, Work: 10 Project 4 - Size:4, Work: x What should I look into to be able to programmatically determine, that Work = Size*3+1 and therefor be able to say that x=13?

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  • How to fix the copy/paste-pattern?

    - by Lenny222
    Where i work, people (consultants) feel pressed to release features as fast as possible. So instead of spending too much time on thinking about how to do things the right way or because they don't want to break anything, code gets copied from different modules and modified. It's not easy to prevent this, since the code base is open to the whole company. Lots of people work on this. Now that the mess is there already, what is the best way to remove those redundancies without breaking too much?

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