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Search found 50247 results on 2010 pages for 'base class'.

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  • Factory Method Pattern using Generics-C#

    - by nanda
    Just I am learning Generics.When i have an Abstract Method pattern like : //Abstract Product interface IPage { string pageType(); } //Concerete Product 1 class ResumePage : IPage { public string pageType() { return "Resume Page"; } } //Concrete Product 2 class SummaryPage : IPage { public string pageType() { return "SummaryPage"; } } //Fcatory Creator class FactoryCreator { public IPage CreateOnRequirement(int i) { if (i == 1) return new ResumePage(); else { return new SummaryPage(); } } } //Client/Consumer void Main() { FactoryCreator c = new FactoryCreator(); IPage p; p = c.CreateOnRequirement(1); Console.WriteLine("Page Type is {0}", p.pageType()); p = c.CreateOnRequirement(2); Console.WriteLine("Page Type is {0}", p.pageType()); Console.ReadLine(); } how to convert the code using generics?

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  • PATH and CLASSPATH in Windows7 7 / Eclipse

    - by Richard Knop
    So I would like to set PATH and CLASSPATH system variables so I can use javac and java commands in the command line. I can just compile and run java programs in eclipse but I would also like to be able to run them through command line. This is where I have Java installed: C:\Program Files (x86)\Java jdk1.6.0_20 jre6 And this is where eclipse stores my Java projects: D:\java-projects HelloWorld bin HelloWorld.class src HelloWorld.java I have set up the PATH and CLASSPATH variables like this: PATH: C:\Program Files (x86)\Java\jdk1.6.0_20\bin CLASSPATH: D:\java-projects But it doesn't work. When I write: java HelloWorld Or: java HelloWorld.class I get error like this: Exception in thread “main” java.lang.NoClassDefFoundError: HelloWorld The error is longer, that's just the first line. How can I fix this? I'm mainly interested to be able to run compiled .class programs from the command line, I can do compiling in the eclipse.

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  • ActiveMQ AJax Client

    - by Lily
    I try to write a simple Ajax client to send and receive messages. It's successfully deployed but I have never received msg from the client. I am beating myself to think out what I am missing, but still can't make it work. Here is my code: I creat a dynamic web application named: ActiveMQAjaxService and put activemq-web.jar and all neccessary dependencies in the WEB-INF/lib folder. In this way, AjaxServlet and MessageServlet will be deployed I start activemq server in command line: ./activemq = activemq successfully created and display: Listening for connections at: tcp://lilyubuntu:61616 INFO | Connector openwire Started INFO | ActiveMQ JMS Message Broker (localhost, ID:lilyubuntu-56855-1272317001405-0:0) started INFO | Logging to org.slf4j.impl.JCLLoggerAdapter(org.mortbay.log) via org.mortbay.log.Slf4jLog INFO | jetty-6.1.9 INFO | ActiveMQ WebConsole initialized. INFO | Initializing Spring FrameworkServlet 'dispatcher' INFO | ActiveMQ Console at http://0.0.0.0:8161/admin INFO | Initializing Spring root WebApplicationContext INFO | Connector vm://localhost Started INFO | Camel Console at http://0.0.0.0:8161/camel INFO | ActiveMQ Web Demos at http://0.0.0.0:8161/demo INFO | RESTful file access application at http://0.0.0.0:8161/fileserver INFO | Started [email protected]:8161 3) index.xml, which is the html to test the client: <?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <script type="text/javascript" src="amq/amq.js"></script> <script type="text/javascript">amq.uri='amq';</script> <title>Hello Ajax ActiveMQ</title> </head> <body> <p>Hello World!</p> <script type="text/javascript"> amq.sendMessage("topic://myDetector", "message"); var myHandler = { rcvMessage: function(message) { alert("received "+message); } }; function myPoll(first) { if (first) { amq.addListener('myDetector', 'topic://myDetector', myHandler.rcvMessage); } } amq.addPollHandler(myPoll); 4) Web.xml: ActiveMQ Web Demos Apache ActiveMQ Web Demos org.apache.activemq.brokerURL vm://localhost (I also tried tcp://localhost:61616) The URL of the Message Broker to connect to org.apache.activemq.embeddedBroker true Whether we should include an embedded broker or not <!-- the subscription REST servlet --> <servlet> <servlet-name>AjaxServlet</servlet-name> <servlet-class>org.apache.activemq.web.AjaxServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet> <servlet-name>MessageServlet</servlet-name> <servlet-class>org.apache.activemq.web.MessageServlet</servlet-class> <load-on-startup>1</load-on-startup> <!-- Uncomment this parameter if you plan to use multiple consumers over REST <init-param> <param-name>destinationOptions</param-name> <param-value>consumer.prefetchSize=1</param-value> </init-param> --> </servlet> <!-- the queue browse servlet --> <filter> <filter-name>session</filter-name> <filter-class>org.apache.activemq.web.SessionFilter</filter-class> </filter> <filter-mapping> <filter-name>session</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> After all of these, I deploy the web-app, and it's successfully deployed, but when I try it out in http://localhost:8080/ActiveMQAjaxService/index.html , nothing happens. I can run the demo portfolioPublisher demo successfully at http://localhost:8161/demo/portfolio/portfolio.html, and see the numbers updated all the time. But for my simple web-app, nothing really works. Any suggestion/hint is welcomed. Thanks so much Lily

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  • How to call a Thor task multiple times?

    - by deepak
    Thor like Rake (and Make) has task management. If I call a task multiple times, it will effectively call the task only once. How can I call a task multiple times? I tried modifying the @_invocations hash, but that did not work: require 'csv' require './config/environment' class MisReport < Thor desc "all", "generate mysql and postgres mis" def all generate("pg_mis_report", "pg") generate("mysql_mis_report", "mysql") end desc "generate", "generate mis report" def generate(file_name = "mis_report_#{Time.now.to_s(:number)}", connection = "postgres") if connection == "pg" puts "== postgres database" ActiveRecord::Base.establish_connection :development_mysql else puts "== mysql database" ActiveRecord::Base.establish_connection :development end # generate MIS puts puts "mis file is at: #{file_path}" end end

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  • Arbitrary attributes error with has_one association and Factory Girl

    - by purpletonic
    I'm trying to build a basic shopping cart for a Rails app I'm working on. Nothing special, - the shopping cart has many line_items - each line_item has_one product associated and a quantity with it class Cart < ActiveRecord::Base attr_accessible :line_items has_many :line_items, :dependent => :destroy end class LineItem < ActiveRecord::Base attr_accessible :quantity, :product belongs_to :cart has_one :product end I'm trying to use RSpec to test this association, but i'm doing something wrong as I'm getting an error that says: DEPRECATION WARNING: You're trying to create an attribute 'line_item_id'. Writing arbitrary attributes on a model is deprecated, and I'm not sure why. In my factories.rb file I'm defining the line_item factory as follows: factory :line_item do quantity { Random.rand(1..5) } product end factory :cart do factory :cart_with_two_line_items do ignore do line_item_count 2 end after(:create) do |cart, evaluator| FactoryGirl.create_list(:line_item, evaluator.line_item_count, cart_id: cart) end end end Any pointers where I'm going wrong, it's probably something basic, but I'm still quite new to Rspec. Thanks in advance.

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  • Don't want to JSON serialize the whole list of classes

    - by mjmcloug
    Hey, I've got a IList of Sites in my application and Site has a large amount of properties. I'm wanting to convert this list to JSON to be used in a dropdownlist similar to this var sites = SiteRepository.FindAllSites(); return new JsonResult() { Data = sites, JsonRequestBehavior = JsonRequestBehavior.AllowGet }; the problem I have is that I only want to use the id and name properties of the site class. I was thinking a way round this would be to use an 'adaptor' class that would then only expose these two properties and I would then serialize that. The problem I have is I want to make the class generic so that it can handle any list of objects. Has anybody come across a similar situation and solved it?

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  • Why can I not deploy my ear on Glassfish

    - by hexin
    I have standard maven project in netbeans (netbeans' enterprise application), that have 1 war, 1 ejb and 1 ear modules. I want to inject with @Inject my @Stateless from ejb to war (REST class) using its interface. I have added some beans.xml files in correct folders in project, but im still getting this: Error occurred during deployment: Exception while loading the app : WELD-001409 Ambiguous dependencies for type [LogicBean] with qualifiers [@Default] at injection point [[field] @Inject private pl.edu.amu.wmi.kino.rk.rest.ReportRest.bean]. Possible dependencies [[Session bean [class pl.edu.amu.wmi.kino.rk.data.impl.LogicBeanImpl with qualifiers [@Any @Default]; local interfaces are [LogicBean], Session bean [class pl.edu.amu.wmi.kino.rk.data.impl.LogicBeanImpl with qualifiers [@Any @Default]; local interfaces are [LogicBean]]]. Please see server.log for more details. What am i doing wrong? I have searched the whole internet, but could not find the solution. I know it is possible because i worked on a project with such a staff. THX for any help:)

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  • user table with javaDB and Hibernate from within grails

    - by Ralf
    let's see if I can ask this in an understandable way... I started with grails and created a domain class called user. As far as I understand, Hibernate is used to map this domain class to the database. This works pretty fine with hsqldb. Now I tried to switch to javaDB and get an error message because the table is called "user" (which seems to be a reserved word for javaDB). So a statement like create table user ... will result in an error message. create table "user" ... works, but Hibernate seems not put put the table name in quotes. How can I configure Hibernate to use quotes in order to make it work with my table name? PS: yes, I know, I could map the domain class to another table name... :-)

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  • How can I force Doxygen to show full include path?

    - by Artyom
    How can I force Doxygen to show full include path? What do I mean: I have a class foo::bar::bee defined in bee.hpp in following directory structure: foo foo/bar foo/bar/bee.hpp Doxygen, when it documents foo::bar::bee class tells that you need to include <bee.hpp>, but for my software I need <foo/bar/bee.hpp> How can I cause Doxygen to do this? Notes: FULL_PATH_NAMES is already set to default YES I do not want to provide include header explicitly for each class, because there too many of them. I want Doxygen to do this automatically. Thanks.

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  • Graphical net and text

    - by chesheerkys
    Hello! My task is to make a control, that behaves itself like RichTextBox, but contains a graphical net. The only task, this net is solving, is to be visible. It should be solution in overriding OnPaint method, but it doesn't. This code: protected override void OnPaint(System.Windows.Forms.PaintEventArgs e) { base.OnPaint(e); ...//drawing a line } gives me RichTextBox without of text This code: protected override void WndProc(ref System.Windows.Forms.Message m) { base.WndProc(ref m); if (m.Msg == 15) { Graphics g = this.CreateGraphics(); g.DrawLine(new Pen(Color.White, 1), new Point(0, 0), new Point(400, 400)); } } sometimes draws extra lines Actually since these two ways don't work, I don't know what to try. Waiting for your advices :) BR Dmitry P.S. I’ve heard a lot about great opportunities of WPF, but I’m not really common with this technology and don’t know what to start with. P.P.S. Sorry for my English, it’s not my natural language.

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  • Create a helper or something for haml with ruby on rails

    - by Lisinge
    Hello, i am using haml with my rails application and i have a question how the easiest way to insert this haml code into a html file: <div clas="holder"> <div class=top"></div> <div class="content"> Content into the div goes here </div> <div class="bottom"></div> </div> And i want to use it in my haml document like this: %html %head %body Maybee some content here. %content_box #I want to get the code i wrote inserted here Content that goes in the content_box like news or stuff %body I hope you understand what i want to acomplish here. And if there is a easier way to do it please answer how. Thanks!

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  • What is this technique called in Java?

    - by ShaChris23
    I'm a C++ programmer, and I was reading this site when I came across the example below. What is this technique called in Java? How is it useful? class Application { ... public void run() { View v = createView(); v.display(); ... protected View createView() { return new View(); } ... } class ApplicationTest extends TestCase { MockView mockView = new MockView(); public void testApplication { Application a = new Application() { <--- protected View createView() { <--- return mockView; <--- whao, what is this? } <--- }; <--- a.run(); mockView.validate(); } private class MockView extends View { boolean isDisplayed = false; public void display() { isDisplayed = true; } public void validate() { assertTrue(isDisplayed); } } }

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  • C#: Inheritance, Overriding, and Hiding

    - by Rosarch
    I'm having difficulty with an architectural decision for my C# XNA game. The basic entity in the world, such as a tree, zombie, or the player, is represented as a GameObject. Each GameObject is composed of at least a GameObjectController, GameObjectModel, and GameObjectView. These three are enough for simple entities, like inanimate trees or rocks. However, as I try to keep the functionality as factored out as possible, the inheritance begins to feel unwieldy. Syntactically, I'm not even sure how best to accomplish my goals. Here is the GameObjectController: public class GameObjectController { protected GameObjectModel model; protected GameObjectView view; public GameObjectController(GameObjectManager gameObjectManager) { this.gameObjectManager = gameObjectManager; model = new GameObjectModel(this); view = new GameObjectView(this); } public GameObjectManager GameObjectManager { get { return gameObjectManager; } } public virtual GameObjectView View { get { return view; } } public virtual GameObjectModel Model { get { return model; } } public virtual void Update(long tick) { } } I want to specify that each subclass of GameObjectController will have accessible at least a GameObjectView and GameObjectModel. If subclasses are fine using those classes, but perhaps are overriding for a more sophisticated Update() method, I don't want them to have to duplicate the code to produce those dependencies. So, the GameObjectController constructor sets those objects up. However, some objects do want to override the model and view. This is where the trouble comes in. Some objects need to fight, so they are CombatantGameObjects: public class CombatantGameObject : GameObjectController { protected new readonly CombatantGameModel model; public new virtual CombatantGameModel Model { get { return model; } } protected readonly CombatEngine combatEngine; public CombatantGameObject(GameObjectManager gameObjectManager, CombatEngine combatEngine) : base(gameObjectManager) { model = new CombatantGameModel(this); this.combatEngine = combatEngine; } public override void Update(long tick) { if (model.Health <= 0) { gameObjectManager.RemoveFromWorld(this); } base.Update(tick); } } Still pretty simple. Is my use of new to hide instance variables correct? Note that I'm assigning CombatantObjectController.model here, even though GameObjectController.Model was already set. And, combatants don't need any special view functionality, so they leave GameObjectController.View alone. Then I get down to the PlayerController, at which a bug is found. public class PlayerController : CombatantGameObject { private readonly IInputReader inputReader; private new readonly PlayerModel model; public new PlayerModel Model { get { return model; } } private float lastInventoryIndexAt; private float lastThrowAt; public PlayerController(GameObjectManager gameObjectManager, IInputReader inputReader, CombatEngine combatEngine) : base(gameObjectManager, combatEngine) { this.inputReader = inputReader; model = new PlayerModel(this); Model.Health = Constants.PLAYER_HEALTH; } public override void Update(long tick) { if (Model.Health <= 0) { gameObjectManager.RemoveFromWorld(this); for (int i = 0; i < 10; i++) { Debug.WriteLine("YOU DEAD SON!!!"); } return; } UpdateFromInput(tick); // .... } } The first time that this line is executed, I get a null reference exception: model.Body.ApplyImpulse(movementImpulse, model.Position); model.Position looks at model.Body, which is null. This is a function that initializes GameObjects before they are deployed into the world: public void Initialize(GameObjectController controller, IDictionary<string, string> data, WorldState worldState) { controller.View.read(data); controller.View.createSpriteAnimations(data, _assets); controller.Model.read(data); SetUpPhysics(controller, worldState, controller.Model.BoundingCircleRadius, Single.Parse(data["x"]), Single.Parse(data["y"]), bool.Parse(data["isBullet"])); } Every object is passed as a GameObjectController. Does that mean that if the object is really a PlayerController, controller.Model will refer to the base's GameObjectModel and not the PlayerController's overriden PlayerObjectModel? In response to rh: This means that now for a PlayerModel p, p.Model is not equivalent to ((CombatantGameObject)p).Model, and also not equivalent to ((GameObjectController)p).Model. That is exactly what I do not want. I want: PlayerController p; p.Model == ((CombatantGameObject)p).Model p.Model == ((GameObjectController)p).Model How can I do this? override?

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  • How to deserialize null array to null in c#?

    - by Aen Sidhe
    Here is my class: public class Command { [XmlArray(IsNullable = true)] public List<Parameter> To { get; set; } } When I serialize an object of this class: var s = new XmlSerializer(typeof(Command)); s.Serialize(Console.Out, new Command()); it prints as expected (xml header and default MS namespaces are omitted): <Command><To xsi:nil="true" /></Command> When I took this xml and tried to deserialize it I got stucked, because it always print "Not null": var t = s.Deserialize(...); if (t.To == null) Console.WriteLine("Null"); else Console.WriteLine("Not null"); How to force deserializer to make my list null, if it is null in xml?

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  • Passing complex objects to javascript via IScriptControl

    - by Jeff Dege
    I'm playing around with a asp.net page that's using the IScriptControl interface to pass data from the code-behind to the custom javascript object running on the browser. I'm passing a number of properties via IScriptControl.GetScriptDescriptors(), and they're all working fine, except for one. That one is a class derived from System.Collections.Generic.Dictionary<. And even that one has been working for me, so long as the elements in the collection were scalars - ints, doubles, and strings. But when I tried to pass a member of a class, it showed up as a null object in the javascript. The class in question is marked [Serializable]. I changed it to a struct, and got the same behavior. It looks as if the serializer used in IScriptControl does a shallow copy. I need a deep copy. Any ideas?

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  • Is it possible to have "inherited partial structs" in c#?

    - by Balazs
    Is it possible to use partial structs to achieve something like this: Have an asp.net page base class with the following defined: public partial struct QuerystringKeys { public const string Username = "username"; public const string CurrentUser = "currentUser"; } Have an asp.net page, which inherits from the base class mentioned above, extend the partial declaration: public partial struct QuerystringKeys { /// <summary> /// The page number of the review instances list /// </summary> public const string Page = "page"; } The final goal is a QuerystringKeys struct with all three constant strings defined in it available to the asp.net page.

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  • NSOpenGLView resize on window resize

    - by ADAM
    I have a class called ModelView which inherits from NSOpenGLView. When my program runs i attach the ModelView as follows to the main window. - (void)applicationDidFinishLaunching:(NSNotification *)aNotification { // Insert code here to initialize your application ModelView *glView; NSRect glViewRect = CGRectMake(0.0f, 0.0f, window.frame.size.width, window.frame.size.height); glView = [[ModelView alloc] initWithFrame: glViewRect]; [[window contentView] addSubview:glView]; } In my ModelView class i have a reshape function which is firing every time the window resizes - (void)reshape { [super setNeedsDisplay:YES]; [[self openGLContext] update]; NSLog(@"reshap function called"); } I want to get the main window width so i can resize the ModelView but i cant find how to get the window width from the ModelView class I am reasonably new to cocoa/objective-c Any help appreciated

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  • Objective-C : Member variable is losing reference between method calls.

    - by Winston
    Hello, I've been having with an objective-c class which appears to be losing its pointer reference between methods of the same class. In the MyTableViewController.h file, I declare: @interface SettingsTableViewController : UITableViewController <UITextFieldDelegate>{ OCRAppDelegate *delegate; } MyTableViewController.m file - (id) init { self = [ super initWithStyle: UITableViewStyleGrouped ]; delegate = [(OCRAppDelegate *)[[UIApplication sharedApplication] delegate] retain]; } The problem is when the "MyTableViewController" view appears again and a different method is executed within that same class, the delegate pointer (which was assigned during the init method) is no longer there. I tried to retain, but to no avail. Would anyone know why this is, it seems like perhaps it is a fundamental Objective-C issue which I am missing. Appreciate your help. Thanks, Winston

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  • C#/ASP.NET MVC 4 Instantiate Object Derived From Interface In Factory Method

    - by Chris
    Currently have a Factory class that features a GetSelector function, which returns a concrete implementation of ISelector. I have several different classes that implement ISelector and based on a setting I would like to receive the appropriate ISelector back. public interface ISelector { string GetValue(string Params); } public class XmlSelector : ISelector { public string GetValue(string Params) { // open XML file and get value } } public static class SelectorFactory { public static ISelector GetSelector() { return new XmlSelector(); // Needs changing to look at settings } } My question is what is the best way to store the setting? I am aware of using AppSettings etc. but I'm not sure whether I want to have to store strings in the web.config and perform a switch on it - just seems to be really tightly coupled in that if a new implementation of ISelector is made, then the Factory would need to be changed. Is there any way of perhaps storing an assembly name and instantiating based on that? Thanks, Chris

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  • JavaScript private methods

    - by Wayne Kao
    To make a JavaScript class with a public method I'd do something like: function Restaurant() { } Restaurant.prototype.buy_food = function() { // something here } Restaurant.prototype.use_restroom = function() { // something here } That way users of my class can: var restaurant = new Restaurant(); restaurant.buy_food(); restaurant.use_restroom(); How do I create a private method that my public buy_food and use_restroom methods can call but that users of the class can't call externally. In other words, I want my method implementation to be able to do: Restaurant.prototype.use_restroom = function() { this.private_stuff(); } But this shouldn't work: var r = new Restaurant(); r.private_stuff(); How do I define private_stuff as a private method so both of those hold true? I've read Doug Crockford's writeup a few times but it doesn't seem like "private" methods can be called by public methods and "privileged" methods can be called externally.

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  • Unmarshalling collections in JaxB

    - by Stas
    Hi, suppose I have this class: public class A { private HashMap<String, B> map; @XmlElement private void setB(ArrayList<B> col) { ... } private ArrayList<B> getB() { ... } } When trying to unmarshall an xml document to this class using JaxB I notice that instead of calling the setB() method and sending me the list of B instances JaxB actually calls the getB() and adds the B instances to the returned list. Why? The reason I want the setter to be called is that the list is actually just a temporary storage from which I want to build the map field, so I thought to do it in the setter. Thanks.

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  • How can I traverse the EMF object tree generated by Xtext?

    - by reprogrammer
    I'm using Xtext to define my DSL. Xtext generates a parser that lets me traverse the EMF model of my input DSL. I'd like to translate this EMF model into some other tree. To do this translation, I need to traverse the tree. But, I couldn't find a visitor class for the EMF model generated by Xtext. The closest thing that I've found is a Switch class that visits a single node. I can traverse the EMF model myself and invoke the Switch class on each node that I visit. But, I wonder if there exists a visitor functionality in Xtext that implements the model traversal.

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  • PHP: Type hints for fields with Eclipse PDT

    - by Silvio Donnini
    Using Eclipse + PDT, I know that you can specify the return type of a method or the type of a variable within a method via type hints. How about class fields? Can I declare the type of a field in order to enable autocompletion for that variable? I tried something on the lines of: class MyClass { protected $Field; /* @var $Field MyType */ ... but it doesn't work. Is there a way to achieve autocompletion of class fields with Eclipse and PDT? thanks, Silvio

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  • Prim's MST algorithm implementation with Java

    - by user1290164
    I'm trying to write a program that'll find the MST of a given undirected weighted graph with Kruskal's and Prim's algorithms. I've successfully implemented Kruskal's algorithm in the program, but I'm having trouble with Prim's. To be more precise, I can't figure out how to actually build the Prim function so that it'll iterate through all the vertices in the graph. I'm getting some IndexOutOfBoundsException errors during program execution. I'm not sure how much information is needed for others to get the idea of what I have done so far, but hopefully there won't be too much useless information. This is what I have so far: I have a Graph, Edge and a Vertex class. Vertex class mostly just an information storage that contains the name (number) of the vertex. Edge class can create a new Edge that has gets parameters (Vertex start, Vertex end, int edgeWeight). The class has methods to return the usual info like start vertex, end vertex and the weight. Graph class reads data from a text file and adds new Edges to an ArrayList. The text file also tells us how many vertecis the graph has, and that gets stored too. In the Graph class, I have a Prim() -method that's supposed to calculate the MST: public ArrayList<Edge> Prim(Graph G) { ArrayList<Edge> edges = G.graph; // Copies the ArrayList with all edges in it. ArrayList<Edge> MST = new ArrayList<Edge>(); Random rnd = new Random(); Vertex startingVertex = edges.get(rnd.nextInt(G.returnVertexCount())).returnStartingVertex(); // This is just to randomize the starting vertex. // This is supposed to be the main loop to find the MST, but this is probably horribly wrong.. while (MST.size() < returnVertexCount()) { Edge e = findClosestNeighbour(startingVertex); MST.add(e); visited.add(e.returnStartingVertex()); visited.add(e.returnEndingVertex()); edges.remove(e); } return MST; } The method findClosesNeighbour() looks like this: public Edge findClosestNeighbour(Vertex v) { ArrayList<Edge> neighbours = new ArrayList<Edge>(); ArrayList<Edge> edges = graph; for (int i = 0; i < edges.size() -1; ++i) { if (edges.get(i).endPoint() == s.returnVertexID() && !visited(edges.get(i).returnEndingVertex())) { neighbours.add(edges.get(i)); } } return neighbours.get(0); // This is the minimum weight edge in the list. } ArrayList<Vertex> visited and ArrayList<Edges> graph get constructed when creating a new graph. Visited() -method is simply a boolean check to see if ArrayList visited contains the Vertex we're thinking about moving to. I tested the findClosestNeighbour() independantly and it seemed to be working but if someone finds something wrong with it then that feedback is welcome also. Mainly though as I mentioned my problem is with actually building the main loop in the Prim() -method, and if there's any additional info needed I'm happy to provide it. Thank you. Edit: To clarify what my train of thought with the Prim() method is. What I want to do is first randomize the starting point in the graph. After that, I will find the closest neighbor to that starting point. Then we'll add the edge connecting those two points to the MST, and also add the vertices to the visited list for checking later, so that we won't form any loops in the graph. Here's the error that gets thrown: Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0 at java.util.ArrayList.rangeCheck(Unknown Source) at java.util.ArrayList.get(Unknown Source) at Graph.findClosestNeighbour(graph.java:203) at Graph.Prim(graph.java:179) at MST.main(MST.java:49) Line 203: return neighbour.get(0); in findClosestNeighbour() Line 179: Edge e = findClosestNeighbour(startingVertex); in Prim()

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  • How to define one-to-many connection between a same model through another model

    - by Mekajiki
    I want to define one-to-many relationship as follows; User has one introducer User has many newcomers(who is introduced by the user) Use "Introduction" model instead of adding a column to users table. My table and model definition is as follows; DB Scheme: create_table "introductions", force: true do |t| t.integer "introducer_id" t.integer "newcomer_id" t.datetime "created_at" t.datetime "updated_at" User model: class User < ActiveRecord::Base has_many :introductions, foreign_key: :introducer_id has_many :newcomers, through: :introductions, source: :newcomer belongs_to :introduction, foreign_key: :newcomer_id belongs_to :introducer end Introduction model: class Introduction < ActiveRecord::Base belongs_to :introducer, class_name: 'User' belongs_to :newcomer, class_name: 'User' end This works fine: user1.newcomers.push user2 but, user2.introducer # => nil How can I define belongs_to relationship correctly?

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