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• Is there a design pattern for this ?

  - by ytrewq

  I have a component that needs to call a specific service depending on the input it receives. So my component has to look at the input and based on a configuration that says "for this input call this service with this data" needs to call the proper service. The services have a common signature method and a specific one (each). I thought about an abstract class that includes the signatures for all three methods. The implementation for the two services will override all three methods (throwing NotImplementedException for the methods that are not supported by current service). A component that could be initialized with a map (that for each input type will have the type of the service to be called) will also be defined. Do you have a better approach to cope this scenario ?

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• IRepository with Inherited Classes

  - by Stacey

  In keeping with the Repository pattern of data input, I've a question in regards to using inherited classes. For instance, suppose I would have the class... class Employee IEmployeeRepository { Add(Employee employee); } This works fine, nothing wrong with it so far... but now let's say I continue on.. class Manager : Employee Okay, now let's assume that I never need to enter a manager different than an Employee? What's the best approach here? Would a scenario such as .. IEmployeeRepository { Add<T>(T employee) where T : Employee } Be the best approach, or do I need to abstract a different repository for each type?

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• How to avoid "incomplete implementation" warning in partial base class

  - by garph0

  I have created a protocol that my classes need to implement, and then factored out some common functionality into a base class, so I did this: @protocol MyProtocol - (void) foo; - (void) bar; @end @interface Base <MyProtocol> @end @interface Derived_1 : Base @end @interface Derived_2 : Base @end @implementation Base - (void) foo{ //something foo } @end @implementation Derived_1 - (void) bar{ //something bar 1 } @end @implementation Derived_2 - (void) bar{ //something bar 2 } @end In this way in my code I use a generic id<MyProtocol>. The code works (as long as Base is not used directly) but the compiler chokes at the end of the implementation of Base with a warning: Incomplete implementation of class Base Is there a way to avoid this warning or, even better, a more proper way to obtain this partially implemented abstract base class behavior in Objc?

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• execute external command / application from java

  - by IttayD

  I'm looking for a package to support reliably executing external processes from Java. My criteria: Abstract over OS. So if I want to run 'foo', it will look for 'foo.bat', 'foo.exe' under windows and 'foo' under other OSs (or, have a way of passing a map of os-command) Being able to execute Java classes by simply giving the class name and arguments (so the package locates the java command, copies jvm flags and then executes) Process stdout and stderr properly Watchdog / Monitoring capabilities I've looked at commons-exec but it looks like it answers only 3 & 4. Ant has support for execution but looks like an overkill to use it for this purpose only.

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• How do I change the class of an object to a subclass of its current class in C++?

  - by Jared P

  I have an array of pointers to a base class, so that I can make those pointers point to (different) subclasses of the base class, but still interact with them. (really only a couple of methods which I made virtual and overloaded) I'm wondering if I can avoid using the pointers, and instead just make an array of the base class, but have some way to set the class to the subclass of my choosing. I know there must be something there specifying the class, as it needs to use that to look up the function pointer for virtual methods. By the way, the subclasses all have the same ivars and layout. Note: the design is actually based on using a template argument instead of a variable, due to performance increases, so really the abstract base class is just the interface for the subclasses, which are all the same except for their compiled code. Thanks

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• Creating a computer with pencil and paper [closed]

  - by Justian Meyer

  This concept has been brought to my attention before, but many people might know it from this popular comic here, where he uses stones instead of points on a paper. This concept is so abstract to me. A full-functioning computer that can manage algorithms, input, output, etc. without electricity? Surely, it's difficult to visualize because my definition of a computer is not exactly what the word sounds like COMPUTE-ER. Can someone help me bring the concept to light - the understanding, how to make one, etc? It seems like it'd be an interesting read, although I think I wouldn't be able to make it do anything. Many thanks in advance for responses. I've tried searching Google, but all I got were ways to diagram code and chart ideas. -.Justian.

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• How to create GUI as inner class with WindowBuilder

  - by Tim Kemp

  I would like to use WindowBuilder in Eclipse to construct Swing GUIs. The JPanels I need to build will be inner classes in a non-GUI wrapper, like so: public class MyWrapper extends MyBaseClass { ... class MyPanel extends JPanel { ... } } So my question is this: can I construct MyPanel using WindowBuilder? If so, how should I set it up? If anyone is interested, the wrapper is an abstract base class which the plug-ins I am developing for my app must extend; deployment concerns mean that it's not really practical to put the GUIs in a separate JAR either so I pretty much have to do it this way. My current workflow, which is awful, is to build the GUI in NetBeans and paste the entire generated class into Eclipse where I connect it up to the methods in my wrapper. I am very hopeful that WindowBuilder will let me work more reliably and efficiently if I can trick it into generating code in MyPanel, not MyWrapper. Thanks

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• Guice child injector override binding

  - by Roman

  Hi All I am trying to to override a binding in a child injector that was already configured in a base injector. like that : public class PersistenceModule extends Abstract{ @Override protected void configure() { bind(IProductPersistenceHelper.class).to(ProductPersistenceHelper.class); } } then : Injector injector = Guice.createInjector(new PersistenceModule()); injector.createChildInjector(new AbstractModule(){ @Override protected void configure() { bind(IProductPersistenceHelper.class).to(MockProductPersistenceHelper.class); } }) Guice is complaining that it has already a binding for that. Are there any patterns or best practices for that problem ?

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• Check if a symlink has changed

  - by BCS

  I have a daemon that, when it's started, loads its data from a directory that happens to be a symlink. Periodically, new data is generated and the symlink updated. I want a bash script that will check if the current symlink is the same as the old one (that the daemon started with) and if not, restart the daemon. My current thought is: if [[ ! -e $old_dir || $(readlink "$data_dir") == $(readlink "$old_dir") ]]; then echo restart ... ln "$(readlink "$data_dir")" "$old_dir" -sf else echo no restart fi The abstract requirement is: each time the script runs, it needs to check if a symlink on a given path now points to a something other than it did the last time and if so do something. (The alternative would be to check if the data at the path has changed but I don't see that being any cleaner.) My questions: Is this a good approach? Does anyone have a better idea? Where should I put $old_dir?

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• JAX-B annotations for elements that inherit from a parent

  - by AlexM

  When adding JAX-B Java annotations for Java classes - if I have a parent Class Entry, with two children, Book and JournalArticle, Would I add these annotations for all three classes: @XmlAccessorType(XmlAccessType.FIELD) @XmlRootElement ie: @XmlSeeAlso({au.com.library.Book.class, au.com.library.JournalArticle.class}) @XmlAccessorType(XmlAccessType.FIELD) @XmlRootElement public abstract class Entry implements Serializable{ private static final long serialVersionUID = -1895155325179947581L; @XmlElement(name="title") protected String title; @XmlElement(name="author") protected String author; @XmlElement(name="year") protected int year; and @XmlAccessorType(XmlAccessType.FIELD) @XmlRootElement public class Book extends Entry { @XmlElement(name="edition") private String edition; @XmlElement(name="publisher") private String publisher; @XmlElement(name="placeOfPublication") private String placeOfPub; and @XmlAccessorType(XmlAccessType.FIELD) @XmlRootElement public class JournalArticle extends Entry { @XmlElement(name="journalTitle") private String journalTitle; @XmlElement(name="volume") private String volume; @XmlElement(name="issue") private String issue; @XmlElement(name="pageNumbers") private String pgNumbers;

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• Interface with generic parameters- can't get it to compile

  - by user997112

  I have an interface like so: public interface MyInterface<E extends Something1> { public void meth1(MyClass1<E> x); } and I have a subclass whose superclass implements the above interface: public class MyClass2<E extends Something1> extends Superclass{ public MyClass2(){ } public void meth1(MyClass1 x) { // TODO Auto-generated method stub } } superclass: public abstract class Superclass<E extends Something1> implements MyInterface{ MyClass1<E> x; protected E y; public Superclass(){ } } the problem is that the parameter for meth1() is supposed to be generic. If I do MyClass1 it doesn't like it and the only way I can get it to compile is by leaving out generic parameters- which feels wrong. What's going wrong?

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• Sharing logic across different platforms

  - by Pranz

  Hello all, We have a business logic that works with the file systems on OS that we want to implement on both Linux and Windows platforms. The language we have selected is Python for Linux and C# for Windows. GUI is not a priority for now. We were looking for ways to abstract the business logic in a way that we dont have to repeat the business logic (ofcourse I understand since it is related to file system, some code will differ from platform to platform). Any ideas on how to implement it? Is C/C++ the only option. We dont want to use Java. Thanks, Pranz

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• Actionscript 3.0 cross-project folder/package structure best practise

  - by dr_tchock

  I'm currently looking at structuring my teams projects into a consistent manner that properly utilises packages and is easily version-controlled (via SVN). I'm interested in any 'best practise' with regards to project structuring and how to use consistent packaging without lumping everything into a gigantic com.domainname.projects folder structure whilst maintaining that package structure. I'm also keen to use the src/bin/lib folder structure within each project. I guess I'm asking 'how do you do it?' and 'why?'. Sorry if this is a bit abstract for Stack Overflow but you guys give the best answers I've found.

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• Is base method able to use derived base data members?

  - by iTayb

  Lets assume we have the following code: abstract class Base1 { protected int num; } class Der1:Base1 { protected Color color; protected string name; } class Der2:Base1 { protected DateTime dthen; } and so on. An array of base1 type exists and includes many objects created out of classes that are derived from base1. Is it possible to define the toString() method in the base class only? something like: public override string toString() { if (this is Der1) return "num = " + this.num + "color = " + this.color.toString() + " name = " this.name; if (this is Der2) return "num = " + this.num + "dthen = " + this.dthen.toString(); // and so on ... } Thank you very much :) P.S. This is not an homework question. I've just wondered about.

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• what is the underlying data structure of a set c++?

  - by zebraman

  I would like to know how a set is implemented in C++. If I were to implement my own set container without using the STL provided container, what would be the best way to go about this task? I understand STL sets are based on the abstract data structure of a binary search tree. So what is the underlying data structure? An array? Also, how does insert() work for a set? How does the set check whether an element already exists in it? I read on wikipedia that another way to implement a set is with a hash table. How would this work?

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• SWIG: Throwing exceptions from Python to C++

  - by wheaties

  We've got an interface we've defined in C++ (abstract class, all functions pure virtual) which will be extended in Python. To overcome the cross-language polymorphism issues we're planning on using SWIG directors. I've read how to catch exceptions thrown from C++ code in our Python code here, here, here, and even on SO. It's fairly straight forward and I'm not expecting issues with handling our library's own exceptions. What I'd like to know and can't seem to find in the documentation is how to have our Python implementation of the extended C++ interface throw those C++ exceptions in a way that makes them visible to the C++ code. We could make small functions within the *.i files such that each function throws our exceptions: void throw_myException(){ throw MyException; } but I'm wondering how it will interact with the Python code. Anyone have any experience with throwing C++ exceptions from Python code?

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• What are the requirements of a collection type when model binding?

  - by Richard Ev

  I have been reviewing model binding with collections, specifically going through this article http://weblogs.asp.net/nmarun/archive/2010/03/13/asp-net-mvc-2-model-binding-for-a-collection.aspx However, the model I would like to use in my code does not implement collections using generic lists. Instead it uses its own collection classes, which inherit from a custom generic collection base class, the declaration of which is public abstract class CollectionBase<T> : IEnumerable<T> The collections in my POSTed action method are all non-null, but contain no elements. Can anyone advise?

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• imageview draw issue with asynctask

  - by alexb

  Have the following asynctask that i'm using to download some images. Works fine except for the very first image, which doesn't always appears unless I do something like move to the next image and then back again. public class DownloadImageTask extends AsyncTask { static ImageView _imageView=null; public DownloadImageTask(ImageView ctl){ _imageView=ctl; } protected void onPostExecute(Bitmap result) { _imageView.setImageBitmap(result); } ... } I thought this might be an issue with updating the UI on a background thread, so I reworked this using an abstract class that invokes a method on the UI thread that calls .setImageBitmap() but I still get the same behaviour - works fine for all images except the first, unless I move to the next image and back again. Is there a way to force a redraw on the imageview after i set the image?

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• Any good class diagram editors out there for Java (not UML)

  - by user85116

  I'm looking for an editor that can create class diagrams, similar to the typical UML class diagram, but specifically for java (so using java terminology; instead of terms like "generalization, realization etc", we use the java equivalents "interface, abstract class, extends etc"). I've looked into UML several times, but each time I've been turned off by the shear amount of "stuff" that comes with UML. I just want to be able to model my java classes quickly and intuitively, without getting bogged down by all the cruft that comes with UML. Preferably, it would come with a source reader that can keep the diagram up to date, and with a few nice features like "show only public methods in this class" etc. As well, it would automatically "know" about the classes in the standard java library, and possibly even be able to read classes from jars. Performance is also a big thing for me, I don't like having to wait 2 seconds for a popup menu to appear, or watch the diagram jerk crazily while resizing an element in the model. What do you think, am I asking too much?

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• What is a good way of coding a file processing program, which accepts multisource data in Java

  - by jjepsuomi

  I'm making a data prosessing system, which currently is using csv-data as input and output form. In the future I might want to add support for example database-, xml-, etc. typed input and output forms. How should I desing my program so that it would be easy to add support for new type of data sources? Should simply make for example an abstract data class (which would contain the basic file prosessing methods) and then inherit this class for database, xml, etc. cases? Hope my question is clear =) In other words my question is: "How to desing a file prosessing system, which can be easily updated to accept input data from different sources (database, XML, Excel, etc.)".

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• Set cookie value before view loaded in MVC?

  - by James123

  I need to set a cookie value before my view called. otherwise I have to refresh the page to get cookie value in the view. The problem here is the value of cookie will get in controller. [HttpGet] [Route("Abstract/{meetingCode}")] [AllowAnonymous] public ActionResult Index(string meetingCode) { var meetingAbstract = new MeetingAbstract(); meetingAbstract.Meeting = _abstractContext.GetMeetingWithMeetingCode(meetingCode); if (meetingAbstract.Meeting != null) { var cookie = new HttpCookie("_culture"); cookie.Value = meetingAbstract.Meeting.language.language_locale_code;//"en-US"; cookie.Expires = DateTime.Now.AddDays(365); cookie.Path = "/"; this.ControllerContext.HttpContext.Response.Cookies.Add(cookie); ... Any other way without refresh the page again to set cookie value?

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• Java: ListA.addAll(ListB) fires NullPointerException?

  - by HH

  The err part is Capitalized in the code, it also comes in foreaching. Because of the abstract list, it cannot be initialized, declaration is in a static field. The lists have the same type. import java.util.*; public class Test { public static final List<String> highPrio = Arrays.asList("*","/"); public static List<String> ops; public static void main(String[] args) { //ERROR HERE, why do it throw nullPointer? ops.addAll(highPrio); for(String s : ops) { System.out.println(s); } } }

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• Composite pattern in C++ problem

  - by annouk

  Hello! I have to work with an application in C++ similar to a phone book: the class Agenda with an STL list of Contacts.Regarding the contacts hierarchy,there is a base-class named Contact(an abstract one),and the derived classes Friend and Acquaintance(the types of contact). These classes have,for instance, a virtual method called getName,which returns the name of the contact. Now I must implement the Composite pattern by adding another type of contact,Company(being derived from Contact),which also contains a collection of Contacts(an STL list as well),that can be either of the "leaf" type(Friends or Acquaintances),or they can be Companies as well. Therefore,Company is the Compound type. The question is: how and where can I implement an STL find_if to search the contact with a given name(via getName function or suggest me smth else) both among the "leaf"-type Contact and inside the Company collection? In other words,how do I traverse the tree in order to find possible matches there too,using an uniform function definition? I hope I was pretty clear...

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• CoreData Model Objects for API

  - by theiOSguy

  I am using CoreData in my application. I want to abstract out all the CoreData related stuff as an API so that the consume can use the API instead of directly using CoreData and its generated model objects. CoreData generates the managed objects model as following @interface Person : NSManagedObject @end I want to define my API for example MyAPI and it has a function called as createPerson:(Person*)p; So the consumer of this createPerson API needs to create a Person data object (like POJO in java world) and invoke this API. But I cannot create Person object using Person *p = [Person alloc] init] because the designated initializer for this Person model created by CoreData does not allow this type of creation. So should I define corresponding user facing data object may be PersonDO and this API should take that instead to carry the data into the API implementation? Is my approach right? Any expert advise if design the API this way is a good design pattern?

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• Using Rails, how can I set my primary key to not be an integer-typed column?

  - by Rudd Zwolinski

  I'm using Rails migrations to manage a database schema, and I'm creating a simple table where I'd like to use a non-integer value as the primary key (in particular, a string). To abstract away from my problem, let's say there's a table employees where employees are identified by an alphanumeric string, e.g. "134SNW". I've tried creating the table in a migration like this: create_table :employees, {:primary_key => :emp_id} do |t| t.string :emp_id t.string :first_name t.string :last_name end What this gives me is what seems like it completely ignored the line t.string :emp_id and went ahead and made it an integer column. Is there some other way to have rails generate the PRIMARY_KEY constraint (I'm using PostgreSQL) for me, without having to write the SQL in an execute call? NOTE: I know it's not best to use string columns as primary keys, so please no answers just saying to add an integer primary key. I may add one anyway, but this question is still valid.

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