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  • PHP class extends not working why and is this how to correctly extend a class?

    - by Matthew
    Hi so I'm trying to understand how inherteince works in PHP using object oriented programming. The main class is Computer, the class that is inheriting is Mouse. I'm extedning the Computer class with the mouse class. I use __construct in each class, when I istinate the class I use the pc type first and if it has mouse after. For some reason computer returns null? why is this? class Computer { protected $type = 'null'; public function __construct($type) { $this->type = $type; } public function computertype() { $this->type = strtoupper($this->type); return $this->type; } } class Mouse extends Computer { protected $hasmouse = 'null'; public function __construct($hasmouse){ $this->hasmouse = $hasmouse; } public function computermouse() { if($this->hasmouse == 'Y') { return 'This Computer has a mouse'; } } } $pc = new Computer('PC', 'Y'); echo $pc->computertype; echo $pc->computermouse;

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  • Hiding elements based on last closed element jquery script

    - by Jared
    Hi my question is, how can I make this jquery script close all previously opened children when entering a new parent? At the moment it traverses thru all the tree structure fine, but switching from one parent to another does not close the previous children, but rather only the each individual parents elements as a user browses. Here is the jquery I'm using: <script type="text/javascript"> $(document).ready($(function(){ $('#nav>li>ul').hide(); $('.children').hide(); $('#nav>li').mousedown(function(){ // check that the menu is not currently animated if ($('#nav ul:animated').size() == 0) { // create a reference to the active element (this) // so we don't have to keep creating a jQuery object $heading = $(this); // create a reference to visible sibling elements // so we don't have to keep creating a jQuery object $expandedSiblings = $heading.siblings().find('ul:visible'); if ($expandedSiblings.size() > 0) { $expandedSiblings.slideUp(0, function(){ $heading.find('ul').slideDown(0); }); } else { $heading.find('ul').slideDown(0); } } }); $('#nav>li>ul>li').mousedown(function(){ // check that the menu is not currently animated if ($('#nav ul:animated').size() == 0) { // create a reference to the active element (this) // so we don't have to keep creating a jQuery object $heading2 = $(this); // create a reference to visible sibling elements // so we don't have to keep creating a jQuery object $expandedSiblings2 = $heading2.siblings().find('.children:visible'); if ($expandedSiblings2.size() > 0) { $expandedSiblings2.slideUp(0, function(){ $heading2.find('.children').slideDown(0); }); } else { $heading2.find('.children').slideDown(0); } } }); })); </script> and here is my html output <ul id="nav"> <li><a href="#">folder 4</a> <ul><li><a href="#">2001</a> <ul><li class="children"><a href="./directory//folder 4/2001/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder 4/2001/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder 4/2001/doc3.txt">doc3.txt</a></li> </ul> </li> <li><a href="#">2002</a> <ul><li class="children"><a href="./directory//folder 4/2002/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder 4/2002/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder 4/2002/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder 4/2002/doc4.txt">doc4.txt</a></li> </ul> </li> <li><a href="#">2003</a> <ul><li class="children"><a href="./directory//folder 4/2003/Copy of doc1.txt">Copy of doc1.txt</a></li> <li class="children"><a href="./directory//folder 4/2003/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder 4/2003/doc2.txt">doc2.txt</a></li> </ul> </li> <li><a href="#">2004</a> <ul><li class="children"><a href="./directory//folder 4/2004/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder 4/2004/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder 4/2004/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder 4/2004/doc4.txt">doc4.txt</a></li> </ul> </li> </ul> </li> <li><a href="#">folder1</a> <ul><li><a href="#">2001</a> <ul><li class="children"><a href="./directory//folder1/2001/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder1/2001/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder1/2001/doc3.txt">doc3.txt</a></li> </ul> </li> <li><a href="#">2002</a> <ul><li class="children"><a href="./directory//folder1/2002/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder1/2002/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder1/2002/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder1/2002/doc4.txt">doc4.txt</a></li> </ul> </li> <li><a href="#">2003</a> <ul><li class="children"><a href="./directory//folder1/2003/Copy of doc1.txt">Copy of doc1.txt</a></li> <li class="children"><a href="./directory//folder1/2003/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder1/2003/doc2.txt">doc2.txt</a></li> </ul> </li> <li><a href="#">2004</a> <ul><li class="children"><a href="./directory//folder1/2004/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder1/2004/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder1/2004/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder1/2004/doc4.txt">doc4.txt</a></li> </ul> </li> </ul> </li> <li><a href="#">folder2</a> <ul><li><a href="#">2001</a> <ul><li class="children"><a href="./directory//folder2/2001/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder2/2001/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder2/2001/doc3.txt">doc3.txt</a></li> </ul> </li> <li><a href="#">2002</a> <ul><li class="children"><a href="./directory//folder2/2002/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder2/2002/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder2/2002/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder2/2002/doc4.txt">doc4.txt</a></li> </ul> </li> <li><a href="#">2003</a> <ul><li class="children"><a href="./directory//folder2/2003/Copy of doc1.txt">Copy of doc1.txt</a></li> <li class="children"><a href="./directory//folder2/2003/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder2/2003/doc2.txt">doc2.txt</a></li> </ul> </li> <li><a href="#">2004</a> <ul><li class="children"><a href="./directory//folder2/2004/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder2/2004/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder2/2004/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder2/2004/doc4.txt">doc4.txt</a></li> </ul> </li> </ul> </li> <li><a href="#">folder3</a> <ul><li><a href="#">2001</a> <ul><li class="children"><a href="./directory//folder3/2001/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder3/2001/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder3/2001/doc3.txt">doc3.txt</a></li> </ul> </li> <li><a href="#">2002</a> <ul><li class="children"><a href="./directory//folder3/2002/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder3/2002/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder3/2002/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder3/2002/doc4.txt">doc4.txt</a></li> </ul> </li> <li><a href="#">2003</a> <ul><li class="children"><a href="./directory//folder3/2003/Copy of doc1.txt">Copy of doc1.txt</a></li> <li class="children"><a href="./directory//folder3/2003/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder3/2003/doc2.txt">doc2.txt</a></li> </ul> </li> <li><a href="#">2004</a> <ul><li class="children"><a href="./directory//folder3/2004/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder3/2004/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder3/2004/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder3/2004/doc4.txt">doc4.txt</a></li> </ul> </li> </ul> </li> </ul> I assume my problem is, jquery isn't closing the children between each new parent so I need to make a call, but I'm a bit lost on how to do that. I know the code is pretty messy, this project was done in a huge rush and a very tight timeframe. Appreciate your answers and any other constructive comments, cheers :)

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  • Extending the IndexController with a BaseController in Zend

    - by BillA
    I'm trying to extend my controllers with a global base controller as such: class BaseController extends Zend_Controller_Action { // common controller actions public function listAction() { // do stuff } } class IndexController extends BaseController { // index controller specific actions } class LoginController extends BaseController { // login controller specific actions } But I get this error: PHP Fatal error: Class 'BaseController' not found in /var/www/Zend/project/application/controllers/IndexController.php on line 3 Any ideas on how to get Zend to "see" this controller?

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  • Combining multiple classes gives me errors

    - by Martti Laine
    Hello I'm creating a website with structure like this: class main { } class mysql extends main { } class user extends main { } class etc extends main { } The idea is for these classes to use functions from each other. This doesn't work. How can I call a function from mysql in user? Martti Laine

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  • IS classOf[] in scala 2.8 different from 2.7?

    - by redtank
    I have an interface from java public class IJava { ... public java.lang.Class getType(); ... } It is inherited in Scala class CScala { def getType() = classOf[Foo] } it worked in scala 2.7.7. But in 2.8.0.RC1, i get type mismatch; found : java.lang.ClassFoo required: java.lang.Class How do i get java.langClass in Scala 2.8

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  • What is the best way to declare sorted association in grails domain classes ?

    - by fabien7474
    It seems that there are two different ways of declaring sorted associations in Grails : Method 1 (see here) using default sort order class Book { String title } class Author { static hasMany = [books : Book] static mapping = { books sort: "title"} } Method 2 (see here) using SortedSet class Book implements Comparable { String title int compareTo(obj) { title <=> obj.title } } class Author { SortedSet books static hasMany = [books : Book] } I am not sure which one to use and what is the difference (if any), pros and cons between using one against the other. I would appreciate any clarification. Thank you

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  • How do I write object classes effectively when dealing with table joins?

    - by Chris
    I should start by saying I'm not now, nor do I have any delusions I'll ever be a professional programmer so most of my skills have been learned from experience very much as a hobby. I learned PHP as it seemed a good simple introduction in certain areas and it allowed me to design simple web applications. When I learned about objects, classes etc the tutor's basic examnples covered the idea that as a rule of thumb each database table should have its own class. While that worked well for the photo gallery project we wrote, as it had very simple mysql queries, it's not working so well now my projects are getting more complex. If I require data from two separate tables which require a table join I've instead been ignoring the class altogether and handling it on a case by case basis, OR, even worse been combining some of the data into the class and the rest as a separate entity and doing two queries, which to me seems inefficient. As an example, when viewing content on a forum I wrote, if you view a thread, I retrieve data from the threads table, the posts table and the user table. The queries from the user and posts table are retrieved via a join and not instantiated as an object, whereas the thread data is called using my Threads class. So how do I get from my current state of affairs to something a little less 'stupid', for want of a better word. Right now I have a DB class that deals with connection and escaping values etc, a parent db query class that deals with the common queries and methods, and all of the other classes (Thread, Upload, Session, Photo and ones thats aren't used Post, User etc ) are children of that. Do I make a big posts class that has the relevant extra attributes that I retrieve from the users (and potentially threads) table? Do I have separate classes that populate each of their relevant attributes with a single query? If so how do I do that? Because of the way my classes are written, based on what I was taught, my db update row method, or insert method both just take the attributes as an array and update all of that, if I have extra attributes from other db tables in each class then how do I rewrite those methods as obbiously updating automatically like that would result in errors? In short I think my understanding is limited right now and I'd like some pointers when it comes to the fundamentals of how to write more complex classes.

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  • Using nested classes for constants?

    - by antirysm
    What's wrong with using nested classes to group constants? Like so: public static class Constants { public static class CategoryA { public const string ValueX = "CatA_X"; public const string ValueY = "CatA_Y"; } public static class CategoryB { public const string ValueX = "CatB_X"; public const string ValueY = "CatB_Y"; } } Used like so: Console.WriteLine(Constants.CategoryA.ValueY); Console.WriteLine(Constants.CategoryB.ValueX); You could also make the "Constants"-class partial...

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  • Using enums in Java across multiple classes

    - by Richard Mar.
    I have the following class: public class Card { public enum Suit { SPACES, HEARTS, DIAMONDS, CLUBS }; public Card(Suit nsuit, int nrank) { suit = nsuit; rank = nrank; } private Suit suit; private int rank; } I want to instantiate it in another class, but that class doesn't understand the Suit enum. Where should I put the enum to make it publicly visible?

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  • Java: Using Dynamically loaded classes

    - by Snigger
    Hi I'm new to java. I'm trying to use some dynamically loaded classes in my application. The application doesn't know classes , Just it try to load a class by name that its name came from input. It doesn't know class (So I can't use casting) but just needs to call some methods of that class (every class should have that methods). I thought about interfaces but I don't know how. How can I call those methods? Thanks

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  • Access specifier's and classes and objects?

    - by TimothyTech
    Alright, im trying to understand this, so a class is simply creating a template for an object. class Bow { int arrows; }; and an object is simply creating a specific item using the class template. Bow::Bow(arrows) { arrows = 20; } also another question, public specifiers are used to make data members avaible in objects and private specifiers are used to make data memebers only avaialble inside the class?

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  • How to reference or connect a variable to another class without stack overflow?

    - by SystemNetworks
    I really need to re-arrange all my functions. I created a class. All my var, booleans, int, doubles and other things. I created every new variable so they can reference it and so they don't have an error. If your asking why I never just reference my main class vars to my sub-class becuase it will give me stack overflow! When in my main class i link my sub-class. subClass s = new subClass(); Then I reference my fake variable to my real variable for example: This is my sub-class variable(I call it fake) public int x = 0; In my main class, I put it like this: s.x = x; The problem is, it does not work! Maybe this is not the right place but I cant ask any questions on stack overflow because they banned me. If I connect my main class and connect my sub-class it will give me stack overflow. How do I stop it?

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  • Injection of an EJB into a web java class under JBoss 7.1.1

    - by Dobbo
    I am trying to build a website using JBoss 7.1.1 and RESTeasy. I have managed to constructed and deploy and EAR with a both a WAR and an EJB-JAR contained within: voyager-app.ear META-INF/MANIFEST.MF META-INF/application.xml META-INF/jboss-app.xml lib/voyager-lib.jar voyager-adm.war voyager-ejb.jar voyager-web.war So far things are very simple. voyager-adm.war & voyager-lib.jar are empty (just the manifest file) but I know that I'm going to have code for them shortly. There is just one Stateful EJB - HarbourMasterBean (with just a local interface) and a few Database Entity Beans in the EJB jar file: voyager-ejb.jar META-INF/MANIFEST.MF META-INF/persistence.xml com/nutrastat/voyager/db/HarbourMasterBean.class com/nutrastat/voyager/db/HarbourMasterLocal.class com/nutrastat/voyager/db/PortEntity.class com/nutrastat/voyager/db/ShipEntity.class As far as I can tell the EJBs deploy correctly because the database units are created and the log shows that the publication of some HarbourMaster references: java:global/voyager-app/voyager-ejb/harbour-master!com.nutrastat.voyager.db.HarbourMasterLocal java:app/voyager-ejb/harbour-master!com.nutrastat.voyager.db.HarbourMasterLocal java:module/harbour-master!com.nutrastat.voyager.db.HarbourMasterLocal java:global/voyager-app/voyager-ejb/harbour-master java:app/voyager-ejb/harbour-master java:module/harbour-master The problem lies in getting the HarbourMaster EJB injected into my web bean. The reference to it is alway NULL no matter what I try. voyager-web.war META-INF/MANIFEST.MF WEB-INF/web.xml WEB-INF/classes/com/nutrastat/voyager/web/ WEB-INF/classes/com/nutrastat/voyager/web/Ships.class WEB-INF/classes/com/nutrastat/voyager/web/VoyagerApplication.class Ships.java: @Path("fleet") public class Ships { protected transient final Logger log; @EJB private HarbourMasterLocal harbourMaster; public Ships() { log = LoggerFactory.getLogger(getClass()); } @GET @Path("ships") @Produces({"text/plain"}) public String listShips() { if (log.isDebugEnabled()) log.debug("Harbour master value: " + harbourMaster); return "Harbour Master: " + harbourMaster; } } &lt;web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0" &gt; <display-name>Voyager Web Application</display-name> <listener> <listener-class> org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap </listener-class> </listener> <servlet> <servlet-name>Resteasy</servlet-name> <servlet-class> org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher </servlet-class> <init-param> <param-name> javax.ws.rs.Application </param-name> <param-value> com.nutrastat.voyager.web.VoyagerApplication </param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>Resteasy</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping> &lt;/web-app&gt; I have been searching the web for an answer and read a number of places, both on StackOverflow and elsewhere that suggests is can be done, and that the problems lies with configuration. But they post only snippets and I'm never sure if I'm doing things correctly. Many thanks for any help you can provide. Dobbo

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  • A Communication System for XAML Applications

    - by psheriff
    In any application, you want to keep the coupling between any two or more objects as loose as possible. Coupling happens when one class contains a property that is used in another class, or uses another class in one of its methods. If you have this situation, then this is called strong or tight coupling. One popular design pattern to help with keeping objects loosely coupled is called the Mediator design pattern. The basics of this pattern are very simple; avoid one object directly talking to another object, and instead use another class to mediate between the two. As with most of my blog posts, the purpose is to introduce you to a simple approach to using a message broker, not all of the fine details. IPDSAMessageBroker Interface As with most implementations of a design pattern, you typically start with an interface or an abstract base class. In this particular instance, an Interface will work just fine. The interface for our Message Broker class just contains a single method “SendMessage” and one event “MessageReceived”. public delegate void MessageReceivedEventHandler( object sender, PDSAMessageBrokerEventArgs e); public interface IPDSAMessageBroker{  void SendMessage(PDSAMessageBrokerMessage msg);   event MessageReceivedEventHandler MessageReceived;} PDSAMessageBrokerMessage Class As you can see in the interface, the SendMessage method requires a type of PDSAMessageBrokerMessage to be passed to it. This class simply has a MessageName which is a ‘string’ type and a MessageBody property which is of the type ‘object’ so you can pass whatever you want in the body. You might pass a string in the body, or a complete Customer object. The MessageName property will help the receiver of the message know what is in the MessageBody property. public class PDSAMessageBrokerMessage{  public PDSAMessageBrokerMessage()  {  }   public PDSAMessageBrokerMessage(string name, object body)  {    MessageName = name;    MessageBody = body;  }   public string MessageName { get; set; }   public object MessageBody { get; set; }} PDSAMessageBrokerEventArgs Class As our message broker class will be raising an event that others can respond to, it is a good idea to create your own event argument class. This class will inherit from the System.EventArgs class and add a couple of additional properties. The properties are the MessageName and Message. The MessageName property is simply a string value. The Message property is a type of a PDSAMessageBrokerMessage class. public class PDSAMessageBrokerEventArgs : EventArgs{  public PDSAMessageBrokerEventArgs()  {  }   public PDSAMessageBrokerEventArgs(string name,     PDSAMessageBrokerMessage msg)  {    MessageName = name;    Message = msg;  }   public string MessageName { get; set; }   public PDSAMessageBrokerMessage Message { get; set; }} PDSAMessageBroker Class Now that you have an interface class and a class to pass a message through an event, it is time to create your actual PDSAMessageBroker class. This class implements the SendMessage method and will also create the event handler for the delegate created in your Interface. public class PDSAMessageBroker : IPDSAMessageBroker{  public void SendMessage(PDSAMessageBrokerMessage msg)  {    PDSAMessageBrokerEventArgs args;     args = new PDSAMessageBrokerEventArgs(      msg.MessageName, msg);     RaiseMessageReceived(args);  }   public event MessageReceivedEventHandler MessageReceived;   protected void RaiseMessageReceived(    PDSAMessageBrokerEventArgs e)  {    if (null != MessageReceived)      MessageReceived(this, e);  }} The SendMessage method will take a PDSAMessageBrokerMessage object as an argument. It then creates an instance of a PDSAMessageBrokerEventArgs class, passing to the constructor two items: the MessageName from the PDSAMessageBrokerMessage object and also the object itself. It may seem a little redundant to pass in the message name when that same message name is part of the message, but it does make consuming the event and checking for the message name a little cleaner – as you will see in the next section. Create a Global Message Broker In your WPF application, create an instance of this message broker class in the App class located in the App.xaml file. Create a public property in the App class and create a new instance of that class in the OnStartUp event procedure as shown in the following code: public partial class App : Application{  public PDSAMessageBroker MessageBroker { get; set; }   protected override void OnStartup(StartupEventArgs e)  {    base.OnStartup(e);     MessageBroker = new PDSAMessageBroker();  }} Sending and Receiving Messages Let’s assume you have a user control that you load into a control on your main window and you want to send a message from that user control to the main window. You might have the main window display a message box, or put a string into a status bar as shown in Figure 1. Figure 1: The main window can receive and send messages The first thing you do in the main window is to hook up an event procedure to the MessageReceived event of the global message broker. This is done in the constructor of the main window: public MainWindow(){  InitializeComponent();   (Application.Current as App).MessageBroker.     MessageReceived += new MessageReceivedEventHandler(       MessageBroker_MessageReceived);} One piece of code you might not be familiar with is accessing a property defined in the App class of your XAML application. Within the App.Xaml file is a class named App that inherits from the Application object. You access the global instance of this App class by using Application.Current. You cast Application.Current to ‘App’ prior to accessing any of the public properties or methods you defined in the App class. Thus, the code (Application.Current as App).MessageBroker, allows you to get at the MessageBroker property defined in the App class. In the MessageReceived event procedure in the main window (shown below) you can now check to see if the MessageName property of the PDSAMessageBrokerEventArgs is equal to “StatusBar” and if it is, then display the message body into the status bar text block control. void MessageBroker_MessageReceived(object sender,   PDSAMessageBrokerEventArgs e){  switch (e.MessageName)  {    case "StatusBar":      tbStatus.Text = e.Message.MessageBody.ToString();      break;  }} In the Page 1 user control’s Loaded event procedure you will send the message “StatusBar” through the global message broker to any listener using the following code: private void UserControl_Loaded(object sender,  RoutedEventArgs e){  // Send Status Message  (Application.Current as App).MessageBroker.    SendMessage(new PDSAMessageBrokerMessage("StatusBar",      "This is Page 1"));} Since the main window is listening for the message ‘StatusBar’, it will display the value “This is Page 1” in the status bar at the bottom of the main window. Sending a Message to a User Control The previous example sent a message from the user control to the main window. You can also send messages from the main window to any listener as well. Remember that the global message broker is really just a broadcaster to anyone who has hooked into the MessageReceived event. In the constructor of the user control named ucPage1 you can hook into the global message broker’s MessageReceived event. You can then listen for any messages that are sent to this control by using a similar switch-case structure like that in the main window. public ucPage1(){  InitializeComponent();   // Hook to the Global Message Broker  (Application.Current as App).MessageBroker.    MessageReceived += new MessageReceivedEventHandler(      MessageBroker_MessageReceived);} void MessageBroker_MessageReceived(object sender,  PDSAMessageBrokerEventArgs e){  // Look for messages intended for Page 1  switch (e.MessageName)  {    case "ForPage1":      MessageBox.Show(e.Message.MessageBody.ToString());      break;  }} Once the ucPage1 user control has been loaded into the main window you can then send a message using the following code: private void btnSendToPage1_Click(object sender,  RoutedEventArgs e){  PDSAMessageBrokerMessage arg =     new PDSAMessageBrokerMessage();   arg.MessageName = "ForPage1";  arg.MessageBody = "Message For Page 1";   // Send a message to Page 1  (Application.Current as App).MessageBroker.SendMessage(arg);} Since the MessageName matches what is in the ucPage1 MessageReceived event procedure, ucPage1 can do anything in response to that event. It is important to note that when the message gets sent it is sent to all MessageReceived event procedures, not just the one that is looking for a message called “ForPage1”. If the user control ucPage1 is not loaded and this message is broadcast, but no other code is listening for it, then it is simply ignored. Remove Event Handler In each class where you add an event handler to the MessageReceived event you need to make sure to remove those event handlers when you are done. Failure to do so can cause a strong reference to the class and thus not allow that object to be garbage collected. In each of your user control’s make sure in the Unloaded event to remove the event handler. private void UserControl_Unloaded(object sender, RoutedEventArgs e){  if (_MessageBroker != null)    _MessageBroker.MessageReceived -=         _MessageBroker_MessageReceived;} Problems with Message Brokering As with most “global” classes or classes that hook up events to other classes, garbage collection is something you need to consider. Just the simple act of hooking up an event procedure to a global event handler creates a reference between your user control and the message broker in the App class. This means that even when your user control is removed from your UI, the class will still be in memory because of the reference to the message broker. This can cause messages to still being handled even though the UI is not being displayed. It is up to you to make sure you remove those event handlers as discussed in the previous section. If you don’t, then the garbage collector cannot release those objects. Instead of using events to send messages from one object to another you might consider registering your objects with a central message broker. This message broker now becomes a collection class into which you pass an object and what messages that object wishes to receive. You do end up with the same problem however. You have to un-register your objects; otherwise they still stay in memory. To alleviate this problem you can look into using the WeakReference class as a method to store your objects so they can be garbage collected if need be. Discussing Weak References is beyond the scope of this post, but you can look this up on the web. Summary In this blog post you learned how to create a simple message broker system that will allow you to send messages from one object to another without having to reference objects directly. This does reduce the coupling between objects in your application. You do need to remember to get rid of any event handlers prior to your objects going out of scope or you run the risk of having memory leaks and events being called even though you can no longer access the object that is responding to that event. NOTE: You can download the sample code for this article by visiting my website at http://www.pdsa.com/downloads. Select “Tips & Tricks”, then select “A Communication System for XAML Applications” from the drop down list.

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  • Explicit method tables in C# instead of OO - good? bad?

    - by FunctorSalad
    Hi! I hope the title doesn't sound too subjective; I absolutely do not mean to start a debate on OO in general. I'd merely like to discuss the basic pros and cons for different ways of solving the following sort of problem. Let's take this minimal example: you want to express an abstract datatype T with functions that may take T as input, output, or both: f1 : Takes a T, returns an int f2 : Takes a string, returns a T f3 : Takes a T and a double, returns another T I'd like to avoid downcasting and any other dynamic typing. I'd also like to avoid mutation whenever possible. 1: Abstract-class-based attempt abstract class T { abstract int f1(); // We can't have abstract constructors, so the best we can do, as I see it, is: abstract void f2(string s); // The convention would be that you'd replace calls to the original f2 by invocation of the nullary constructor of the implementing type, followed by invocation of f2. f2 would need to have side-effects to be of any use. // f3 is a problem too: abstract T f3(double d); // This doesn't express that the return value is of the *same* type as the object whose method is invoked; it just expresses that the return value is *some* T. } 2: Parametric polymorphism and an auxilliary class (all implementing classes of TImpl will be singleton classes): abstract class TImpl<T> { abstract int f1(T t); abstract T f2(string s); abstract T f3(T t, double d); } We no longer express that some concrete type actually implements our original spec -- an implementation is simply a type Foo for which we happen to have an instance of TImpl. This doesn't seem to be a problem: If you want a function that works on arbitrary implementations, you just do something like: // Say we want to return a Bar given an arbitrary implementation of our abstract type Bar bar<T>(TImpl<T> ti, T t); At this point, one might as well skip inheritance and singletons altogether and use a 3 First-class function table class /* or struct, even */ TDictT<T> { readonly Func<T,int> f1; readonly Func<string,T> f2; readonly Func<T,double,T> f3; TDict( ... ) { this.f1 = f1; this.f2 = f2; this.f3 = f3; } } Bar bar<T>(TDict<T> td; T t); Though I don't see much practical difference between #2 and #3. Example Implementation class MyT { /* raw data structure goes here; this class needn't have any methods */ } // It doesn't matter where we put the following; could be a static method of MyT, or some static class collecting dictionaries static readonly TDict<MyT> MyTDict = new TDict<MyT>( (t) => /* body of f1 goes here */ , // f2 (s) => /* body of f2 goes here */, // f3 (t,d) => /* body of f3 goes here */ ); Thoughts? #3 is unidiomatic, but it seems rather safe and clean. One question is whether there are any performance concerns with it. I don't usually need dynamic dispatch, and I'd prefer if these function bodies get statically inlined in places where the concrete implementing type is known statically. Is #2 better in that regard?

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  • Cheetah with Cherrypy: how to load base templates, and do so automatically on change during developm

    - by Heikki Toivonen
    I am working on a cherrypy+cheetah app and would like to improve the development experience. I have everything working when I manually compile templates beforehand. However, during development I'd rather just load the templates every time they are referenced so that I don't need to kill and restart my application. I have a couple of issues I am facing: If I have templates inheriting from base templates, I get import errors (can't find base templates). I think I had this actually working during my experiments, but unfortunately didn't save it and now I can't make it work. Suppose I get 1. working, how do make it so that edits even in base templates get picked up without restart. Below is my sample application that should demonstrate the problems. The directory structure is as follows: t.py templates/ base.tmpl index.tmpl t.py: import sys import cherrypy from Cheetah.Template import Template class T: def __init__(self, foo): self.foo = foo @cherrypy.expose def index(self): return Template(file='templates/index.tmpl', searchList=[{'foo': self.foo}]).respond() cherrypy.quickstart(T(sys.argv[1])) base.tmpl: #def body This is the body from the base #end def This is the base doc index.tmpl: #from templates.base import base #extends base #def body $base.body(self) This is the extended body #end def This is from index Run it like this: python t.py Something

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  • Custom Wordpress Post Page Breaks if More Thank 2 Posts?

    - by thatryan
    I have a very custom template, and it works great if there are 1 or 2 posts on the blog page. But as soon as a 3rd post is added, it alters the structure of the template... Literally moves a div inside of another and I can not understand why. The code for the blog template is here, and a screenshot of the structure as it should be and another showing the misplaced div when a third post is there. Does this make any sense, any ideas? Thank you much! <div class="post" id="post-<?php the_ID(); ?>"><!--start post--> <h2><?php the_title(); ?></h2> <div id="main_full" class=" clearfix"><!--start main--> <div id="top_bar"><h3 class="gallery-title">news</h3></div> <div id="blog_page"><!--start blog page--> <div class="entry"><!--start entry--> <?php the_content(); ?> </div><!--end entry--> </div><!--end blog page--> </div><!--end main--> <?php endwhile; endif; ?> </div><!--end post--> <?php edit_post_link('Edit this entry.', '<p>', '</p>'); ?> <?php comments_template(); ?> Good One Bad One

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  • Unable to get values in ftl from value stack in custom Result Type

    - by Nagadev
    Hello, I am unable retrieve value from value stack in FTL file. Here is the code. Action class holds a property called 'name' private String name; public String getName() { return name; } public void setName(String name) { this.name = name; } public String execute(){ setName("From value stack .. "); return SUCCESS; } FTL code: ${name} Custom result Type deExecute Method Configuration configuration = new Configuration(); String templatePath = "/ftl"; ServletContext context = ServletActionContext.getServletContext(); configuration.setServletContextForTemplateLoading(context, templatePath); configuration.setObjectWrapper(new DefaultObjectWrapper()); Template template = configuration.getTemplate("sample.ftl"); OutputStreamWriter out = new OutputStreamWriter(System.out); template.process(ActionContext.getContext().getValueStack(), out); I am passing the value Stack which contains recently executed Action as well. But FTL is throwing an exception Expression name is undefined on line 1, column 3 in sample.ftl I tried with passing session instead of value stack and I could get the value in FTL. Please suggest me a way to get values from Action class to FTL from value stack. Thanks inadvance.

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  • Django templatetag "order of processing"

    - by Jason Persampieri
    I am trying to write a set of template tags that allow you to easily specify js and css files from within the template files themselves. Something along the lines of {% requires global.css %}, and later in the request, {% get_required_css %}. I have this mostly working, but there are a couple of issues. We'll start with the 'timing' issues. Each template tag is made up of two steps, call/init and render. Every call/init happens before any render procedure is called. In order to guarantee that all of the files are queued before the {% get_required_css %} is rendered, I need to build my list of required files in the call/init procedures themselves. So, I need to collect all of the files into one bundle per request. The context dict is obviously the place for this, but unfortunately, the call/init doesn't have access to the context variable. Is this making sense? Anyone see a way around this (without resorting to a hack-y global request object)? Another possibility to store these in a local dict but they would still need to be tied to the request somehow... possibly some sort of {% start_requires %} tag? But I have no clue how to make that work either.

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  • Efficiently get the size of a parameter pack up to a certain index

    - by NmdMystery
    I want to be able to determine the number of bytes that are in a subset of a parameter pack from 0 to a given index. Right now I'm using a non-constexpr way of doing this. Below is my code: template <size_t index, typename... args> struct pack_size_index; template <size_t index, typename type_t, typename... args> struct pack_size_index <index, type_t, args...> { static const size_t index_v = index; static const size_t value(void) { if (index_v > 0) { return sizeof(type_t) + pack_size_index<index - 1, args...>::value(); } return 0; } }; template <size_t index> struct pack_size_index <index> { static const size_t index_v = index; static const size_t value(void) { return 0; } }; Usage: //output: 5 (equal to 1 + 4) std::cout << pack_size_index<2, bool, float, int, double>::value() << std::endl; //output: 20 (equal to 8 + 8 + 4) std::cout << pack_size_index<3, double, double, float, int>::value() << std::endl; This gets the job done, but this uses runtime comparison and the resulting executable increases in size rapidly whenever this is used. What's a less expensive way of doing this?

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  • Jeopardy template for Silverlight

    - by Mohit Deshpande
    I am supposed to be making a jeopardy game for my class. I was wondering it there is a template for it already out? Or do I have to make one myself, in which case, what would be the best approach to making this game in Silverlight? (My last resort is to make it in PowerPoint)

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  • Validation does not work when I use Validator.TryValidateObject.

    - by ashraf
    DataAnnotations does not work with buddy class. The following code always validate true. Why ? var isValid = Validator.TryValidateObject(new Customer(), Context, results, true); and here is the buddy class. public partial class Customer { public string Name { get; set; } public int Age { get; set; } } [MetadataType(typeof(CustomerMetaData))] public partial class Customer { public class CustomerMetaData { [Required(ErrorMessage = "You must supply a name for a customer.")] public string Name { get; set; } } } Here is another thread with same question., but no answer. link text

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