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• MixItUp Pagination not working

  - by pwnjack

  I'm using MixItUp in my project to have an homepage with my items, and I want a pagination, i saw that the plugin actually supports pagination but I couldn't make it work. Here is my attempt: Markup: <div id="main"> <div class="container" id="Container"> <div class="row"> <div class="col-md-3 mix clip"> <div class="item"> <img src="http://placehold.it/300x200" class="img-responsive" alt=""> <div class="caption"> <h1>Title</h1> <p>Videoclip</p> </div> </div> </div> <div class="col-md-3 mix adv"> <div class="item"> <img src="http://placehold.it/300x200" class="img-responsive" alt=""> <div class="caption"> <h1>Title</h1> <p>Advertising</p> </div> </div> </div> <div class="col-md-3 mix reportage"> <div class="item"> <img src="http://placehold.it/300x200" class="img-responsive" alt=""> <div class="caption"> <h1>Title</h1> <p>Reportage</p> </div> </div> </div> <div class="col-md-3 mix clip"> <div class="item"> <img src="http://placehold.it/300x200" class="img-responsive" alt=""> <div class="caption"> <h1>Title</h1> <p>Videoclip</p> </div> </div> </div> <div class="col-md-3 mix adv"> <div class="item"> <img src="http://placehold.it/300x200" class="img-responsive" alt=""> <div class="caption"> <h1>Title</h1> <p>Advertising</p> </div> </div> </div> <div class="col-md-3 mix reportage"> <div class="item"> <img src="http://placehold.it/300x200" class="img-responsive" alt=""> <div class="caption"> <h1>Title</h1> <p>Reportage</p> </div> </div> </div> <div class="col-md-3 mix clip"> <div class="item"> <img src="http://placehold.it/300x200" class="img-responsive" alt=""> <div class="caption"> <h1>Title</h1> <p>Videoclip</p> </div> </div> </div> <div class="col-md-3 mix adv"> <div class="item"> <img src="http://placehold.it/300x200" class="img-responsive" alt=""> <div class="caption"> <h1>Title</h1> <p>Advertising</p> </div> </div> </div> <div class="col-md-3 mix reportage"> <div class="item"> <img src="http://placehold.it/300x200" class="img-responsive" alt=""> <div class="caption"> <h1>Title</h1> <p>Videoclip</p> </div> </div> </div> <div class="col-md-3 mix clip"> <div class="item"> <img src="http://placehold.it/300x200" class="img-responsive" alt=""> <div class="caption"> <h1>Title</h1> <p>Videoclip</p> </div> </div> </div> <div class="col-md-3 mix adv"> <div class="item"> <img src="http://placehold.it/300x200" class="img-responsive" alt=""> <div class="caption"> <h1>Title</h1> <p>Advertising</p> </div> </div> </div> <div class="col-md-3 mix reportage"> <div class="item"> <img src="http://placehold.it/300x200" class="img-responsive" alt=""> <div class="caption"> <h1>Title</h1> <p>Reportage</p> </div> </div> </div> </div> <!-- end row --> </div> <!-- end container --> </div> <!-- end main --> As you can see the plugin is working fine with filters, but the pagination is not even showing. In the plugin's documentation there's a section dedicated to pagination, although the demo example is not there, so i can't use it as a starting working point. You can take a look at the documentation here: https://mixitup.kunkalabs.com/extensions/pagination I followed the instructions and used this JS code: $('#Container').mixItUp({ pagination: { generatePagers: true, prevButtonHTML: '«', nextButtonHTML: '»' } }); I put in the markup the emtpy div as stated in the docs: <div class="pager-list"> <!-- Pagination buttons will be generated here --> </div> Nothing happens. Can someone point me in the right direction, I don't know how to go on solving this problem, the plugin seems to support pagination, so I'm hoping to achieve that. Thanks, any suggestion is much appreciated.

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• Translate Java class with static attributes and Annotation to Scala equivalent

  - by ifischer

  I'm currently trying to "translate" the following Java class to an equivalent Scala class. It's part of a JavaEE6-application and i need it to use the JPA2 MetaModel. import javax.persistence.metamodel.SingularAttribute; import javax.persistence.metamodel.StaticMetamodel; @StaticMetamodel(Person.class) public class Person_ { public static volatile SingularAttribute<Person, String> name; } A dissassembling of the compiled class file reveals the following information for the compiled file: > javap Person_.class : public class model.Person_ extends java.lang.Object{ public static volatile javax.persistence.metamodel.SingularAttribute name; public model.Person_(); } So now i need an equivalent Scala file that has the same structure, as JPA depends on it, cause it resolves the attributes by reflection to make them accessible at runtime. So the main problem i think is that the attribute is static, but the Annotation has to be on an (Java)Object (i guess) My first naive attempt to create a Scala equivalent is the following: @StaticMetamodel(classOf[Person]) class Person_ object Person_ { @volatile var name:SingularAttribute[Person, String] = _; } But the resulting classfile is far away from the Java one, so it doesn't work. When trying to access the attributes at runtime, e.g. "Person_.firstname", it resolves to null, i think JPA can't do the right reflection magic on the compiled classfile (the Java variant resolves to an instance of org.hibernate.ejb.metamodel.SingularAttributeImpl at runtime). > javap Person_.class : public class model.Person_ extends java.lang.Object implements scala.ScalaObject{ public static final void name_$eq(javax.persistence.metamodel.SingularAttribute); public static final javax.persistence.metamodel.SingularAttribute name(); public model.Person_(); } > javap Person_$.class : public final class model.Person__$ extends java.lang.Object implements scala.ScalaObject public static final model.Person__$ MODULE$; public static {}; public javax.persistence.metamodel.SingularAttribute name(); public void name_$eq(javax.persistence.metamodel.SingularAttribute); } So now what i'd like to know is if it's possible at all to create a Scala equivalent of the Java class? It seems to me that it's absolutely not, but maybe there is a workaround or something (except just using Java, but i want my app to be in Scala where possible) Any ideas, anyone? Thanks in advance!

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• Can there be two public section in a class? If yes then why ? And in which circumstances we do so?

  - by Abhi

  Dear all I have a doubt related to class. For example class A { public: A() { ..... ..... } void cleanup() { .... .... .... } public: UINT a; ULONG b; }; In the above example there are two public section, In first section i am defining constructor and the method and in the second section i am declaring data members. Does the above class i.e. A is correct. Can we do so? If yes then why we needed and in which circumstances we should use it? Also we can do the entire thing in one section then why un necessary we r taking two section...? Thanks and regards Abhineet Agarwal

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• How to infer the type of a derived class in base class?

  - by enzi

  I want to create a method that allows me to change arbitrary properties of classes that derive from my base class, the result should look like this: SetPropertyValue("size.height", 50); – where size is a property of my derived class and height is a property of size. I'm almost done with my implementation but there's one final obstacle that I want to solve before moving on, to describe this I will first have to explain my implementation a bit: Properties that can be modified are decorated with an attribute There's a method in my base class that searches for all derived classes and their decorated properties For each property I generate a "property modifier", a class that contains 2 delegates: one to set and one to get the value of the property. Property Modifiers are stored in a dictionary, with the name of the property as key In my base class, there is another dictionary that contains all property-modifier-dictionaries, with the Type of the respective class as key. What the SetPropertyValue method does is this: Get the correct property-modifier-dictionary, using the concrete type of the derived class (<- yet to solve) Get the property modifier of the property to change (e.g. of the property size) Use the get or set delegate to modify the property's value Some example code to clarify further: private static Dictionary<RuntimeTypeHandle, object> EditableTypes; //property-modifier-dictionary protected void SetPropertyValue<T>(EditablePropertyMap<T> map, string property, object value) { var property = map[property]; // get the property modifier property.Set((T)this, value); // use the set delegate (encapsulated in a method) } In the above code, T is the Type of the actual (derived) class. I need this type for the get/set delegates. The problem is how to get the EditablePropertyMap<T> when I don't know what T is. My current (ugly) solution is to pass the map in an overriden virtual method in the derived class: public override void SetPropertyValue(string property, object value) { base.SetPropertyValue((EditablePropertyMap<ExampleType>)EditableTypes[typeof(ExampleType)], property, value); } What this does is: get the correct dictionary containing the property modifiers of this class using the class's type, cast it to the appropiate type and pass it to the SetPropertyValue method. I want to get rid of the SetPropertyValue method in my derived class (since there are a lot of derived classes), but don't know yet how to accomplish that. I cannot just make a virtual GetEditablePropertyMap<T> method because I cannot infer a concrete type for T then. I also cannot acces my dictionary directly with a type and retrieve an EditablePropertyMap<T> from it because I cannot cast to it from object in the base class, since again I do not know T. I found some neat tricks to infere types (e.g. by adding a dummy T parameter), but cannot apply them to my specific problem. I'd highly appreciate any suggestions you may have for me.

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• Extend base class properties

  - by user1888033

  I need your help to extend my base class, here is the similar structure i have. public class ShowRoomA { public audi AudiModelA { get; set; } public benz benzModelA { get; set; } } public class audi { public string Name { get; set; } public string AC { get; set; } public string PowerStearing { get; set; } } public class benz { public string Name { get; set; } public string AC { get; set; } public string AirBag { get; set; } public string MusicSystem { get; set; } } //My Implementation class like this class Main() { private void UpdateDetails() { ShowRoomA ojbMahi = new ShowRoomA(); GetDetails( ojbMahi ); // this works fine } private void GetDetails(ShowRoomA objShowRoom) { objShowRoom = new objShowRoom(); objShowRoom.audi = new audi(); objShowRoom.audi.Name = "AUDIMODEL94CD698"; objShowRoom.audi.AC = "6 TON"; objShowRoom.audi.PowerStearing = "Electric"; objShowRoom.benz= new benz(); objShowRoom.audi.Name = "BENZMODEL34LCX"; objShowRoom.audi.AC = "8 TON"; objShowRoom.audi.AirBag = "Two (1+1)"; objShowRoom.audi.MusicSystem = "Poineer 3500W"; } } // Till this cool. // Now I got requirement for ShowRoomB with replacement of old audi and benz with new models and new other brand cars also added. // I don't want to modify GetDetails() method. by reusing this method additional logic i want to apply to my new extended model. // Here I struck in designing my new model of ShowRoomB (base of ShowRoomA) ... I have tried some thing like... but not sure. public class audiModelB:audi { public string JetEngine { get; set; } } public class benzModelB:benz { public string JetEngine { get; set; } } public class ShowRoomB { public audiModelB AudiModelB { get; set; } public benzModelB benzModelB { get; set; } } // My new code to Implementation class like this class Main() { private void UpdateDetails() { ShowRoomB ojbNahi = new ShowRoomB(); GetDetails( ojbNahi ); // this is NOT working! I know this object does not contain base class directly, still some what i want fill my new model with old properties. Kindly suggest here } } Can any one please give me solutions how to achieve my extending requirement for base class "ShowroomA" Really appreciated your time and suggestions. Thanks in advance,

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• layout is not included in all pages in asp.net mvc4 application

  - by Ahmed

  I am developing an asp.net mvc4 application with Bootstrap 3 and i've _Layout.cshtml in "Shared" folder , in Views, i've two pages, "Index and "Register" and i've included Layout in both of these Views but It seems that Layout is included in only "Index and not in "Register" View. Following are my Index and Register Views @{ ViewBag.Title = "Index"; Layout = "~/Views/Shared/_Layout.cshtml"; } <h2 align="center" class="bg-info">Login</h2> <form class="form-horizontal" role="form"> <div class="form-group"> <label for="inputEmail3" class="col-sm-2 control-label"><strong>UserName : </strong></label> <div class="col-sm-10"> <input type="email" class="form-control" id="inputEmail3" placeholder="UserName"> </div> </div> <div class="form-group"> <label for="inputPassword3" class="col-sm-2 control-label"><strong>Password</strong></label> <div class="col-sm-10"> <input type="password" class="form-control" id="inputPassword3" placeholder="Password"> </div> </div> <div class="form-group"> <div class="col-sm-offset-2 col-sm-10"> <div class="checkbox"> <label> <input type="checkbox"> Remember me </label> </div> </div> </div> <div class="form-group"> <div class="col-sm-offset-2 col-sm-10"> <button type="submit" class="btn btn-primary">Sign in</button> </div> </div> <h2 align="center" class="bg-info">SignIn With Other Services</h2> </form> <form class="form-horizontal" role="form" method="post" action="/Home/FacebookLogin"> <div class="form-group"> <div class="col-sm-offset-2 col-sm-10"> <button type="submit" class="btn btn-primary">SignIn with Facebook</button> </div> </div> </form> <h2 align="center" class="bg-info">Don't Have an Account?</h2> <form class="form-horizontal" role="form" method="post" action="/Home/Register"> <div class="form-group"> <div class="col-sm-offset-2 col-sm-10"> <button type="submit" class="btn btn-primary">Register</button> </div> </div> </form> ![@{ ViewBag.Title = "Register"; Layout = "~/Views/Shared/_Layout.cshtml"; } <h2 align="center" class="bg-info">Register</h2> <form class="form-horizontal" role="form"> <div class="form-group"> <label for="inputEmail3" class="col-sm-2 control-label"><strong>UserName : </strong></label> <div class="col-sm-10"> <input type="email" class="form-control" id="uname" name="uname" placeholder="UserName"> <input type="button" class="btn btn-primary" id="check" value="Check Availability" > <h4 class="bg-warning"></h4> </div> </div> <div class="form-group"> <label for="inputPassword3" class="col-sm-2 control-label"><strong>Password</strong></label> <div class="col-sm-10"> <input type="password" class="form-control" id="upass" name="upass" placeholder="Password"> </div> </div> <div class="form-group"> <label for="inputPassword3" class="col-sm-2 control-label"><strong>Retype Password</strong></label> <div class="col-sm-10"> <input type="password" class="form-control" id="retype" placeholder="Password"> </div> </div> <div class="form-group"> <div class="col-sm-offset-2 col-sm-10"> <button type="submit" class="btn btn-primary">Register</button> </div> </div> </form>]

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• ASP.NET MVC2 - usage of LINQ-generated class (validation problem)

  - by ile

  There are few things not clear to me about ASP.NET MV2. In database I have table Contacts with several fields, and there is an additional field XmlFields of which type is xml. In that field are stored additional description fields. There are 4 classes: Contact class which corresponds to Contact table and is defined by default when creating LINQ classes ContactListView class which inherits Contact class and has some additional properties ContactXmlView class that contains fields from XmlFields field ContactDetailsView class which merges ContactListView and ContactXmlView into one class and this one is used to display data in view pages ContactListView class has re-defined some properties from Contact class (so that I can add [Required] filter used for validation) - but I get warning message: 'ObjectTest.Models.Contacts.ContactListView.FirstName' hides inherited member 'SA.Model.Contact.FirstName'. Use the new keyword if hiding was intended. ContactDetailsView class is also used in a form when creating new contact and adding it to database. I am not sure if this is correct way, and the warning message confuses me a bit. Any advise about this? Thanks, Ile EDIT According to Jakob's instructions I tried it from scratch: [MetadataType(typeof(Person_Validation))] public partial class Person { } public class Person_Validation { [Required] string FirstName { get; set; } [Required] string LastName { get; set; } [Required] int Age { get; set; } } In Controller I have this: [HttpPost] public ActionResult Create(Person person, FormCollection collection) { if (ModelState.IsValid) { try { personRepository.Add(person); personRepository.Save(); } catch { return View(person); } } return RedirectToAction("Index"); } View: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<Validate.Models.Person>" %> <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server"> Create </asp:Content> <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> <h2>Create</h2> <% using (Html.BeginForm()) {%> <%= Html.ValidationSummary(true) %> <fieldset> <legend>Fields</legend> <div class="editor-label"> <%= Html.LabelFor(model => model.FirstName) %> </div> <div class="editor-field"> <%= Html.TextBoxFor(model => model.FirstName) %> <%= Html.ValidationMessageFor(model => model.FirstName) %> </div> <div class="editor-label"> <%= Html.LabelFor(model => model.LastName) %> </div> <div class="editor-field"> <%= Html.TextBoxFor(model => model.LastName) %> <%= Html.ValidationMessageFor(model => model.LastName) %> </div> <div class="editor-label"> <%= Html.LabelFor(model => model.Age) %> </div> <div class="editor-field"> <%= Html.TextBoxFor(model => model.Age) %> <%= Html.ValidationMessageFor(model => model.Age) %> </div> <p> <input type="submit" value="Create" /> </p> </fieldset> <% } %> <div> <%= Html.ActionLink("Back to List", "Index") %> </div> </asp:Content> When posting new person with no values, nothing happens (page is just reloaded). When posting with some values, person is added to db. I have no idea what am I doing wrong.

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• Javascript - How to index html code into variables

  - by Fernando SBS

  The webpage has the following source (only copied the important part): <h1>Relatórios</h1> <div id="textmenu"> <a href="berichte.php" class="selected ">Tudo</a> | <a href="berichte.php?t=2">Comércio</a> | <a href="berichte.php?t=1">Reforços</a> | <a href="berichte.php?t=3">Ataques</a> | <a href="berichte.php?t=4">Outros</a> </div> <form method="post" action="berichte.php" name="msg"> <table cellpadding="1" cellspacing="1" id="overview" class="row_table_data"> <thead> <tr> <th colspan="2">Assunto:</th> <th class="sent"> enviada</th> </tr> </thead><tfoot> <tr> <th>&nbsp;</th> <th class=buttons><input name=del value=apagar alt=apagar type=image id=btn_delete class=dynamic_img src=img/x.gif /></th> <th class=navi>&laquo;<a href="berichte.php?s=10&amp;o=0">&raquo;</a></th> </tr> </tfoot> <tbody> <tr> <td class="sel"><input class="check" type="checkbox" name="n1" value="15737030" /></td> <td class="sub"><img src="img/x.gif" class="iReport iReport1" alt="Ganhou como atacante sem perdas" title="Ganhou como atacante sem perdas" /> <div><a href="berichte.php?id=15737030">Rio Grande Do Leste ataca lcsanchez da aldeia</a> </div> </td> <td class="dat">hoje 21:33</td> </tr> <tr> <td class="sel"><input class="check" type="checkbox" name="n2" value="15736877" /></td> <td class="sub"><img src="img/x.gif" class="iReport iReport1" alt="Ganhou como atacante sem perdas" title="Ganhou como atacante sem perdas" /> <div><a href="berichte.php?id=15736877">Rio Grande Do Leste ataca Thabiti da aldeia</a> </div> </td> <td class="dat">hoje 21:32</td> </tr> <tr> <td class="sel"><input class="check" type="checkbox" name="n3" value="15736759" /></td> <td class="sub"><img src="img/x.gif" class="iReport iReport1" alt="Ganhou como atacante sem perdas" title="Ganhou como atacante sem perdas" /> <div><a href="berichte.php?id=15736759">Rio Grande Do Leste ataca Dionisio</a> </div> </td> <td class="dat">hoje 21:31</td> </tr> <tr> <td class="sel"><input class="check" type="checkbox" name="n4" value="15736513" /></td> <td class="sub"><img src="img/x.gif" class="iReport iReport1" alt="Ganhou como atacante sem perdas" title="Ganhou como atacante sem perdas" /> <div><a href="berichte.php?id=15736513">Rio Grande Do Leste ataca Aldeia de troakris</a> (nova)</div> </td> <td class="dat">hoje 21:30</td> </tr> <tr> <td class="sel"><input class="check" type="checkbox" name="n5" value="15736275" /></td> <td class="sub"><img src="img/x.gif" class="iReport iReport1" alt="Ganhou como atacante sem perdas" title="Ganhou como atacante sem perdas" /> <div><a href="berichte.php?id=15736275">Rio Grande Do Leste ataca Thabiti da aldeia</a> </div> </td> <td class="dat">hoje 21:28</td> </tr> <tr> <td class="sel"><input class="check" type="checkbox" name="n6" value="15736220" /></td> <td class="sub"><img src="img/x.gif" class="iReport iReport1" alt="Ganhou como atacante sem perdas" title="Ganhou como atacante sem perdas" /> <div><a href="berichte.php?id=15736220">Rio Grande Do Leste ataca Aldeia de troakris</a> (nova)</div> </td> <td class="dat">hoje 21:28</td> </tr> <tr> <td class="sel"><input class="check" type="checkbox" name="n7" value="15734824" /></td> <td class="sub"><img src="img/x.gif" class="iReport iReport1" alt="Ganhou como atacante sem perdas" title="Ganhou como atacante sem perdas" /> <div><a href="berichte.php?id=15734824">Rio Grande Do Leste ataca Austrália</a> </div> </td> <td class="dat">hoje 21:18</td> </tr> <tr> <td class="sel"><input class="check" type="checkbox" name="n8" value="15734440" /></td> <td class="sub"><img src="img/x.gif" class="iReport iReport1" alt="Ganhou como atacante sem perdas" title="Ganhou como atacante sem perdas" /> <div><a href="berichte.php?id=15734440">Rio Grande Do Leste ataca andrômeda</a> (nova)</div> </td> <td class="dat">hoje 21:15</td> </tr> <tr> <td class="sel"><input class="check" type="checkbox" name="n9" value="15730612" /></td> <td class="sub"><img src="img/x.gif" class="iReport iReport1" alt="Ganhou como atacante sem perdas" title="Ganhou como atacante sem perdas" /> <div><a href="berichte.php?id=15730612">Rio Grande Do Leste ataca wLG02 KING OF POP</a> (nova)</div> </td> <td class="dat">hoje 20:49</td> </tr> <tr> <td class="sel"><input class="check" type="checkbox" name="n10" value="15730304" /></td> <td class="sub"><img src="img/x.gif" class="iReport iReport1" alt="Ganhou como atacante sem perdas" title="Ganhou como atacante sem perdas" /> <div><a href="berichte.php?id=15730304">Rio Grande Do Leste ataca wLG02 KING OF POP</a> (nova)</div> </td> <td class="dat">hoje 20:47</td> </tr> </tbody> </table> </form> </div> I want to read from the source and assign to a variable the values like: relatorio[0] = berichte.php?id=15730304; relatorio[1] = berichte.php?id=15730612; ... relatorio[9] = berichte.php?id=15737030; How to do that? thanks

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• C++ visibility of privately inherited typedefs to nested classes

  - by beldaz

  First time on StackOverflow, so please be tolerant. In the following example (apologies for the length) I have tried to isolate some unexpected behaviour I've encountered when using nested classes within a class that privately inherits from another. I've often seen statements to the effect that there is nothing special about a nested class compared to an unnested class, but in this example one can see that a nested class (at least according to GCC 4.4) can see the public typedefs of a class that is privately inherited by the closing class. I appreciate that typdefs are not the same as member data, but I found this behaviour surprising, and I imagine many others would, too. So my question is threefold: Is this standard behaviour? (a decent explanation of why would be very helpful) Can one expect it to work on most modern compilers (i.e., how portable is it)? #include <iostream> class Base { typedef int priv_t; priv_t priv; public: typedef int pub_t; pub_t pub; Base() : priv(0), pub(1) {} }; class PubDerived : public Base { public: // Not allowed since Base::priv is private // void foo() {std::cout << priv << "\n";} class Nested { // Not allowed since Nested has no access to PubDerived member data // void foo() {std::cout << pub << "\n";} // Not allowed since typedef Base::priv_t is private // void bar() {priv_t x=0; std::cout << x << "\n";} }; }; class PrivDerived : private Base { public: // Allowed since Base::pub is public void foo() {std::cout << pub << "\n";} class Nested { public: // Works (gcc 4.4 - see below) void fred() {pub_t x=0; std::cout << x << "\n";} }; }; int main() { // Not allowed since typedef Base::priv_t private // std::cout << PubDerived::priv_t(0) << "\n"; // Allowed since typedef Base::pub_t is inaccessible std::cout << PubDerived::pub_t(0) << "\n"; // Prints 0 // Not allowed since typedef Base::pub_t is inaccessible //std::cout << PrivDerived::pub_t(0) << "\n"; // Works (gcc 4.4) PrivDerived::Nested o; o.fred(); // Prints 0 return 0; }

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• Why would Java classloading fail on Linux, but succeed on Windows?

  - by arnsholt

  I've got a Java web application (using Spring), deployed with Jetty. If I try to run it on a Windows machine everything works as expected, but if I try to run the same code on my Linux machine, it fails like this: [normal startup output] 11:16:39.657 INFO [main] org.mortbay.jetty.servlet.ServletHandler$Context.log(ServletHandler.java:1145) 16 Set web app root system property: 'webapp.root' = [/path/to/working/dir] java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.mortbay.start.Main.invokeMain(Main.java:151) at org.mortbay.start.Main.start(Main.java:476) at org.mortbay.start.Main.main(Main.java:94) Caused by: java.lang.ExceptionInInitializerError at org.springframework.web.util.Log4jWebConfigurer.initLogging(Log4jWebConfigurer.java:129) at org.springframework.web.util.Log4jConfigListener.contextInitialized(Log4jConfigListener.java:51) at org.mortbay.jetty.servlet.WebApplicationContext.doStart(WebApplicationContext.java:495) at org.mortbay.util.Container.start(Container.java:72) at org.mortbay.http.HttpServer.doStart(HttpServer.java:708) at org.mortbay.util.Container.start(Container.java:72) at org.mortbay.jetty.Server.main(Server.java:460) ... 7 more Caused by: org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: No suitable Log constructor [Ljava.lang.Class;@15311bd for org.apache.commons.logging.impl.Log4JLogger (Caused by java.lang.NoClassDefFoundError: org/apache/log4j/Category) (Caused by org.apache.commons.logging.LogConfigurationException: No suitable Log constructor [Ljava.lang.Class;@15311bd for org.apache.commons.logging.impl.Log4JLogger (Caused by java.lang.NoClassDefFoundError: org/apache/log4j/Category)) at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:543) at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:235) at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:209) at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:351) at org.springframework.util.SystemPropertyUtils.(SystemPropertyUtils.java:42) ... 14 more Caused by: org.apache.commons.logging.LogConfigurationException: No suitable Log constructor [Ljava.lang.Class;@15311bd for org.apache.commons.logging.impl.Log4JLogger (Caused by java.lang.NoClassDefFoundError: org/apache/log4j/Category) at org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:413) at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:529) ... 18 more Caused by: java.lang.NoClassDefFoundError: org/apache/log4j/Category at java.lang.Class.getDeclaredConstructors0(Native Method) at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389) at java.lang.Class.getConstructor0(Class.java:2699) at java.lang.Class.getConstructor(Class.java:1657) at org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:410) ... 19 more Caused by: java.lang.ClassNotFoundException: org.apache.log4j.Category at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at java.lang.ClassLoader.loadClass(ClassLoader.java:252) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) ... 24 more [shutdown output] I've run the app with java -verbose:class, and according to that output, org.apache.log4j.Category is loaded from the log4j JAR in my /WEB-INF/lib, just before the first exception is thrown. Now, the Java versions on the two machines are slightly different. Both the machines have Sun's java, the Linux machine has 1.6.0_10, while the Windows machine has 1.6.0_08, or maybe 07 or 06, I can't remember the exact number right now, and don't have the machine at hand. But even though the minor versions of the Javas are slightly different, the code shouldn't break like this. Does anyone understand what's wrong here?

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• A DirectoryCatalog class for Silverlight MEF (Managed Extensibility Framework)

  - by Dixin

  In the MEF (Managed Extension Framework) for .NET, there are useful ComposablePartCatalog implementations in System.ComponentModel.Composition.dll, like: System.ComponentModel.Composition.Hosting.AggregateCatalog System.ComponentModel.Composition.Hosting.AssemblyCatalog System.ComponentModel.Composition.Hosting.DirectoryCatalog System.ComponentModel.Composition.Hosting.TypeCatalog While in Silverlight, there is a extra System.ComponentModel.Composition.Hosting.DeploymentCatalog. As a wrapper of AssemblyCatalog, it can load all assemblies in a XAP file in the web server side. Unfortunately, in silverlight there is no DirectoryCatalog to load a folder. Background There are scenarios that Silverlight application may need to load all XAP files in a folder in the web server side, for example: If the Silverlight application is extensible and supports plug-ins, there would be a /ClinetBin/Plugins/ folder in the web server, and each pluin would be an individual XAP file in the folder. In this scenario, after the application is loaded and started up, it would like to load all XAP files in /ClinetBin/Plugins/ folder. If the aplication supports themes, there would be a /ClinetBin/Themes/ folder, and each theme would be an individual XAP file too. The application would qalso need to load all XAP files in /ClinetBin/Themes/. It is useful if we have a DirectoryCatalog: DirectoryCatalog catalog = new DirectoryCatalog("/Plugins"); catalog.DownloadCompleted += (sender, e) => { }; catalog.DownloadAsync(); Obviously, the implementation of DirectoryCatalog is easy. It is just a collection of DeploymentCatalog class. Retrieve file list from a directory Of course, to retrieve file list from a web folder, the folder’s “Directory Browsing” feature must be enabled: So when the folder is requested, it responses a list of its files and folders: This is nothing but a simple HTML page: <html> <head> <title>localhost - /Folder/</title> </head> <body> <h1>localhost - /Folder/</h1> <hr> <pre> <a href="/">[To Parent Directory]</a><br> <br> 1/3/2011 7:22 PM 185 <a href="/Folder/File.txt">File.txt</a><br> 1/3/2011 7:22 PM &lt;dir&gt; <a href="/Folder/Folder/">Folder</a><br> </pre> <hr> </body> </html> For the ASP.NET Deployment Server of Visual Studio, directory browsing is enabled by default: The HTML <Body> is almost the same: <body bgcolor="white"> <h2><i>Directory Listing -- /ClientBin/</i></h2> <hr width="100%" size="1" color="silver"> <pre> <a href="/">[To Parent Directory]</a> Thursday, January 27, 2011 11:51 PM 282,538 <a href="Test.xap">Test.xap</a> Tuesday, January 04, 2011 02:06 AM &lt;dir&gt; <a href="TestFolder/">TestFolder</a> </pre> <hr width="100%" size="1" color="silver"> <b>Version Information:</b>&nbsp;ASP.NET Development Server 10.0.0.0 </body> The only difference is, IIS’s links start with slash, but here the links do not. Here one way to get the file list is read the href attributes of the links: [Pure] private IEnumerable<Uri> GetFilesFromDirectory(string html) { Contract.Requires(html != null); Contract.Ensures(Contract.Result<IEnumerable<Uri>>() != null); return new Regex( "<a href=\"(?<uriRelative>[^\"]*)\">[^<]*</a>", RegexOptions.IgnoreCase | RegexOptions.CultureInvariant) .Matches(html) .OfType<Match>() .Where(match => match.Success) .Select(match => match.Groups["uriRelative"].Value) .Where(uriRelative => uriRelative.EndsWith(".xap", StringComparison.Ordinal)) .Select(uriRelative => { Uri baseUri = this.Uri.IsAbsoluteUri ? this.Uri : new Uri(Application.Current.Host.Source, this.Uri); uriRelative = uriRelative.StartsWith("/", StringComparison.Ordinal) ? uriRelative : (baseUri.LocalPath.EndsWith("/", StringComparison.Ordinal) ? baseUri.LocalPath + uriRelative : baseUri.LocalPath + "/" + uriRelative); return new Uri(baseUri, uriRelative); }); } Please notice the folders’ links end with a slash. They are filtered by the second Where() query. The above method can find files’ URIs from the specified IIS folder, or ASP.NET Deployment Server folder while debugging. To support other formats of file list, a constructor is needed to pass into a customized method: /// <summary> /// Initializes a new instance of the <see cref="T:System.ComponentModel.Composition.Hosting.DirectoryCatalog" /> class with <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePartDefinition" /> objects based on all the XAP files in the specified directory URI. /// </summary> /// <param name="uri"> /// URI to the directory to scan for XAPs to add to the catalog. /// The URI must be absolute, or relative to <see cref="P:System.Windows.Interop.SilverlightHost.Source" />. /// </param> /// <param name="getFilesFromDirectory"> /// The method to find files' URIs in the specified directory. /// </param> public DirectoryCatalog(Uri uri, Func<string, IEnumerable<Uri>> getFilesFromDirectory) { Contract.Requires(uri != null); this._uri = uri; this._getFilesFromDirectory = getFilesFromDirectory ?? this.GetFilesFromDirectory; this._webClient = new Lazy<WebClient>(() => new WebClient()); // Initializes other members. } When the getFilesFromDirectory parameter is null, the above GetFilesFromDirectory() method will be used as default. Download the directory’s XAP file list Now a public method can be created to start the downloading: /// <summary> /// Begins downloading the XAP files in the directory. /// </summary> public void DownloadAsync() { this.ThrowIfDisposed(); if (Interlocked.CompareExchange(ref this._state, State.DownloadStarted, State.Created) == 0) { this._webClient.Value.OpenReadCompleted += this.HandleOpenReadCompleted; this._webClient.Value.OpenReadAsync(this.Uri, this); } else { this.MutateStateOrThrow(State.DownloadCompleted, State.Initialized); this.OnDownloadCompleted(new AsyncCompletedEventArgs(null, false, this)); } } Here the HandleOpenReadCompleted() method is invoked when the file list HTML is downloaded. Download all XAP files After retrieving all files’ URIs, the next thing becomes even easier. HandleOpenReadCompleted() just uses built in DeploymentCatalog to download the XAPs, and aggregate them into one AggregateCatalog: private void HandleOpenReadCompleted(object sender, OpenReadCompletedEventArgs e) { Exception error = e.Error; bool cancelled = e.Cancelled; if (Interlocked.CompareExchange(ref this._state, State.DownloadCompleted, State.DownloadStarted) != State.DownloadStarted) { cancelled = true; } if (error == null && !cancelled) { try { using (StreamReader reader = new StreamReader(e.Result)) { string html = reader.ReadToEnd(); IEnumerable<Uri> uris = this._getFilesFromDirectory(html); Contract.Assume(uris != null); IEnumerable<DeploymentCatalog> deploymentCatalogs = uris.Select(uri => new DeploymentCatalog(uri)); deploymentCatalogs.ForEach( deploymentCatalog => { this._aggregateCatalog.Catalogs.Add(deploymentCatalog); deploymentCatalog.DownloadCompleted += this.HandleDownloadCompleted; }); deploymentCatalogs.ForEach(deploymentCatalog => deploymentCatalog.DownloadAsync()); } } catch (Exception exception) { error = new InvalidOperationException(Resources.InvalidOperationException_ErrorReadingDirectory, exception); } } // Exception handling. } In HandleDownloadCompleted(), if all XAPs are downloaded without exception, OnDownloadCompleted() callback method will be invoked. private void HandleDownloadCompleted(object sender, AsyncCompletedEventArgs e) { if (Interlocked.Increment(ref this._downloaded) == this._aggregateCatalog.Catalogs.Count) { this.OnDownloadCompleted(e); } } Exception handling Whether this DirectoryCatelog can work only if the directory browsing feature is enabled. It is important to inform caller when directory cannot be browsed for XAP downloading. private void HandleOpenReadCompleted(object sender, OpenReadCompletedEventArgs e) { Exception error = e.Error; bool cancelled = e.Cancelled; if (Interlocked.CompareExchange(ref this._state, State.DownloadCompleted, State.DownloadStarted) != State.DownloadStarted) { cancelled = true; } if (error == null && !cancelled) { try { // No exception thrown when browsing directory. Downloads the listed XAPs. } catch (Exception exception) { error = new InvalidOperationException(Resources.InvalidOperationException_ErrorReadingDirectory, exception); } } WebException webException = error as WebException; if (webException != null) { HttpWebResponse webResponse = webException.Response as HttpWebResponse; if (webResponse != null) { // Internally, WebClient uses WebRequest.Create() to create the WebRequest object. Here does the same thing. WebRequest request = WebRequest.Create(Application.Current.Host.Source); Contract.Assume(request != null); if (request.CreatorInstance == WebRequestCreator.ClientHttp && // Silverlight is in client HTTP handling, all HTTP status codes are supported. webResponse.StatusCode == HttpStatusCode.Forbidden) { // When directory browsing is disabled, the HTTP status code is 403 (forbidden). error = new InvalidOperationException( Resources.InvalidOperationException_ErrorListingDirectory_ClientHttp, webException); } else if (request.CreatorInstance == WebRequestCreator.BrowserHttp && // Silverlight is in browser HTTP handling, only 200 and 404 are supported. webResponse.StatusCode == HttpStatusCode.NotFound) { // When directory browsing is disabled, the HTTP status code is 404 (not found). error = new InvalidOperationException( Resources.InvalidOperationException_ErrorListingDirectory_BrowserHttp, webException); } } } this.OnDownloadCompleted(new AsyncCompletedEventArgs(error, cancelled, this)); } Please notice Silverlight 3+ application can work either in client HTTP handling, or browser HTTP handling. One difference is: In browser HTTP handling, only HTTP status code 200 (OK) and 404 (not OK, including 500, 403, etc.) are supported In client HTTP handling, all HTTP status code are supported So in above code, exceptions in 2 modes are handled differently. Conclusion Here is the whole DirectoryCatelog’s looking: Please click here to download the source code, a simple unit test is included. This is a rough implementation. And, for convenience, some design and coding are just following the built in AggregateCatalog class and Deployment class. Please feel free to modify the code, and please kindly tell me if any issue is found.

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• New Oracle Tutor Class: Create Procedures and Support Documents

  - by [email protected]

  Offered by Oracle University Course Code D66797GC10 July 14-16, 2010 in Chicago, IL This three day Instructor Led class is only US$ 2,250 Oracle® Tutor provides organizations with a powerful pair of applications to develop, deploy, and maintain employee business process documentation. Tutor includes a repository of prewritten process, procedure, and support documents that can be readily modified to reflect your company's unique business processes. The result is a set of job-role specific desk manuals that are easy to update and deploy online. Use Tutor to create content to: Implement new business applications Document for any regulatory compliance initiative Turn every desk into a self service reference center Increase employee productivity The primary challenge for companies faced with documenting policies, processes, and procedures is to realize that they can do this documentation in-house, with existing resources, using Oracle Tutor. Process documentation is a critical success component when implementing or upgrading to a new business application and for supporting corporate governance or other regulatory compliance initiatives. There are over 1000 Oracle Tutor customers worldwide that have used Tutor to create, distribute, and maintain their business procedures. This is easily accomplished because of Tutor's: Ease of use by those who have to write procedures (Microsoft Word based authoring) Ease of company-wide implementation (complex document management activities are centralized) Ease of use by workers who have to follow the procedures (play script format) Ease of access by remote workers (web-enabled) This course is an introduction to the Oracle Tutor suite of products. It focuses on the process documentation feature set of the Tutor applications. Participants will learn about writing procedures and maintaining these particular process document types, all using the Tutor method. Audience Business Analysts End Users Functional Implementer Project Manager Sales Consultants Security Compliance Auditors User Adoption Consultants Prerequisites No Prerequisite Courses strong working knowledge of MS Windows strong working knowledge of MS Word (2007) Objectives • Provide your organization with the next steps to implement the Tutor procedure writing method and system in your organization • Use the Tutor Author application to write employee focused process documents (procedures, instructions, references, process maps) • Use the Tutor Publisher application to create impact analysis reports, Employee Desk Manuals, and Owner Manuals Web site on OU Link to a PDF of the class summary Oracle University Training Centre - Chicago Emily Chorba Product Manager for Oracle Tutor

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• Naming a class that decides to retrieve things from cache or a service + architecture evaluation

  - by Thomas Stock

  Hi, I'm a junior developer and I'm working on a pet project that I want to learn as much as possible from. I have the following scenario: There's a WCF service that I use to retrieve and update data, lets say Cars. So it's called CarWCFService and has a GetCars(), SaveCar(), ... . It implements interface ICarService. This isn't the Actual WCF service but more like a wrapper around it. Upon retrieving data from the service, I want to store them in local memory, as cache. I have made a class for this called CarCacheService which also implements interface ICarService. (I will explain later why it implements ICarService) I don't want client code to be calling these implementations. Instead, I want to create a third implementation for ICarService that tries to read from the CarCacheService before calling the WCFCarService, stores retrieved data in the CarCacheService, etc. 3 questions: How do I name this third class? I was thinking about something as simple as CarService. This does not really says what the service does exactly, tho. Is the naming for the other classes good? Would this naming and architecture be obvious for future programmers? This is my biggest concern. Does this architecture make sense? The reason that I implement ICarService on the CarCacheService is mainly because it allows me to fake the WCFService while debugging. I can store dummy data in a CarCacheService instance and pass it to the CarService, together with an(other) empty CarCacheService. If I made CacheCarService and WCFService public I could let client code decide if they want to drop the caching and just work directly on the WCFService.

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• Best design for a "Command Executer" class

  - by Justin984

  Sorry for the vague title, I couldn't think of a way to condense the question. I am building an application that will run as a background service and intermittently collect data about the system its running on. A second Android controller application will query the system over tcp/ip for statistics about the system. Currently, the background service has a tcp listener class that reads/writes bytes from a socket. When data is received, it raises an event to notify the service. The service takes the bytes, feeds them into a command parser to figure out what is being requested, and then passes the parsed command to a command executer class. When the service receives a "query statistics" command, it should return statistics over the tcp/ip connection. Currently, all of these classes are fully decoupled from each other. But in order for the command executer to return statistics, it will obviously need access to the socket somehow. For reasons I can't completely articulate, it feels wrong for the command executer to have a direct reference to the socket. I'm looking for strategies and/or design patterns I can use to return data over the socket while keeping the classes decoupled, if this is possible. Hopefully this makes sense, please let me know if I can include any info that would make the question easier to understand.

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• Java: How to Make a Player Class in a Tile-Based RPG

  - by A.K.

  So I've been following a JavaHub tutorial that basically uses a pixel engine similar to MiniCraft. I've attempted to make a Player Class as such, and I'm basically making a mock Pokemon game for learning's sake: package pokemon.entity; import java.awt.Rectangle; import pokemon.gfx.Screen; import pokemon.levelgen.Tile; import pokemon.entity.SpritesManage;; public class Player { int x, y; int vx, vy; public Rectangle AshRec; public Sprite AshSprite; Screen screen; Sprite[][] AshSheet; public Player() { AshSprite = SpritesManage.AshSheet[1][0]; AshRec = new Rectangle(0, 0, 16, 16); x = 0; y = 0; vx = 1; vy = 1; screen.renderSprite(0, 0, AshSprite); } public void update() { move(); checkCollision(); } private void checkCollision() { } private void move() { AshRec.x += vx; AshRec.y += vy; } public void render(Screen screen, int x, int y) { screen.renderSprite(x, y, AshSprite); } } I guess what I really want to do is have the Player centered in the screen and have the sprite drawn based on an Input Handler. I'm just stumped as to how to sync these together.

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• Creating shooting arrow class [on hold]

  - by I.Hristov

  OK I am trying to write an XNA game with one controllable by the player entity, while the rest are bots (enemy and friendly) wondering around and... shooting each other from range. Now the shooting I suppose should be done with a separate class Arrow (for example). The resulting object would be the arrow appearing on screen moving from shooting entity to target entity. When target is reached arrow is no longer active, probably removed from the list. I plan to make a class with fields: Vector2 shootingEntity; Vector2 targetEntity; float arrowSpeed; float arrowAttackSpeed; int damageDone; bool isActive; Then when enemy entities get closer than a int rangeToShoot (which each entity will have as a field/prop) I plan to make a list of arrows emerging from each entity and going to the closest opposite one. I wonder if that logic will enable me later to make possible many entities to be able to shoot independently at different enemy entities at the same time. I know the question is broad but it would be wise to ask if the foundations of the idea are correct.

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• Updated Business Activity Monitoring (BAM) Class

  - by Gary Barg

  We have just completed an extensive upgrade to the Business Activity Monitoring course, bringing it up to PS5 level and doing some major rework of content and topic flow. This should be a GREAT course for anyone needing to learn to use BAM effectively to analyze their SOA data. Details of the Course This course explains how to use Oracle BAM to monitor enterprise business activities across an enterprise in real time. You can measure your key performance indicators (KPIs), determine whether you are meeting service-level agreements (SLAs), and take corrective action in real time. Learn To: Create dashboards and alerts using a business-friendly, wizard-based design environment Monitor BPM and BPEL processes Configure drilling, driving, and time-based filtering Create alerts Build applications with a dynamic user interface Manage BAM users and roles In addition to learning Oracle BAM architecture, you learn how to perform administrative tasks related to Oracle BAM. You create and work with the different types of message sources that send data into Oracle BAM. You build interactive, real-time, actionable dashboards, and you configure alerts on abnormal conditions. You learn how to monitor both BPEL and BPM composite applications with Oracle BAM. Lastly, you create and use Oracle BAM data control to build applications with a dynamic user interface that changes based on real-time business events. Registration The Oracle University course page with more course details and registration information, is here. The next scheduled class: Date: 5-Dec-2012 Duration: 3 days Hours: 9:00 AM – 5:00 PM CT Location: Chicago, IL Class ID: 3325708

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• Should I use a seperate class per test?

  - by user460667

  Taking the following simple method, how would you suggest I write a unit test for it (I am using MSTest however concepts are similar in other tools). public void MyMethod(MyObject myObj, bool validInput) { if(!validInput) { // Do nothing } else { // Update the object myObj.CurrentDateTime = DateTime.Now; myObj.Name = "Hello World"; } } If I try and follow the rule of one assert per test, my logic would be that I should have a Class Initialise method which executes the method and then individual tests which check each property on myobj. public class void MyTest { MyObj myObj; [TestInitialize] public void MyTestInitialize() { this.myObj = new MyObj(); MyMethod(myObj, true); } [TestMethod] public void IsValidName() { Assert.AreEqual("Hello World", this.myObj.Name); } [TestMethod] public void IsDateNotNull() { Assert.IsNotNull(this.myObj.CurrentDateTime); } } Where I am confused is around the TestInitialize. If I execute the method under TestInitialize, I would need seperate classes per variation of parameter inputs. Is this correct? This would leave me with a huge number of files in my project (unless I have multiple classes per file). Thanks

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• How to handle class dependency with interfaces and implementatons

  - by lealand

  I'm using ObjectAid with Eclipse to generate UML class diagrams for my latest Java project, and I currently have a handful of situations like this, where I have a dependency between two interfaces, as well as one of the implementations of one of the interfaces. Here, foo is the graphics library I'm using. In the previous example, FooCanvas draws ITexture objects to the screen, and both FooCanvas and its interface, ICanvas, take ITexture objects as arguments to their methods. The method in the canvas classes which cause this dependency is the following: void drawTexture(ITexture texture, float x, float y); Additionally, I tried a variation on the method signature using Java's generics: <T extends ITexture> void drawTexture(T texture, float x, float y); The result of this was a class diagram where the only dependencies where between the interfaces and the implementing classes, and no dependency by a canvas object on a texture. I'm not sure if this is more ideal or not. Is the dependency of both the interface and implementation on another interface an expected pattern, or is it typical and/or possible to keep the implementation 'isolated' from its interfaces dependencies? Or is the generic method the ideal solution?

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• How to "wrap" implementation in C#

  - by igor

  Hello, I have these classes in C# (.NET Framework 3.5) described below: public class Base { public int State {get; set;} public virtual int Method1(){} public virtual string Method2(){} ... public virtual void Method10(){} } public class B: Base { // some implementation } public class Proxy: Base { private B _b; public class Proxy(B b) { _b = b; } public override int Method1() { if (State == Running) return _b.Method1(); else return base.Method1(); } public override string Method2() { if (State == Running) return _b.Method2(); else return base.Method2(); } public override void Method10() { if (State == Running) _b.Method10(); else base.Method10(); } } I want to get something this: public Base GetStateDependentImplementation() { if (State == Running) // may be some other rule return _b; else return base; // compile error } and my Proxy's implementation will be: public class Proxy: Base { ... public override int Method1() { return GetStateDependentImplementation().Method1(); } public override string Method2() { return GetStateDependentImplementation().Method2(); } ... } Of course, I can do this (aggregation of base implementation): public RepeaterOfBase: Base // no any overrides, just inheritance { } public class Proxy: Base { private B _b; private RepeaterOfBase _Base; public class Proxy(B b, RepeaterOfBase aBase) { _b = b; _base = aBase; } } ... public Base GetStateDependentImplementation() { if (State == Running) return _b; else return _Base; } ... But instance of Base class is very huge and I have to avoid to have other additional copy in memory. So I have to simplify my code have to "wrap" implementation have to avoid a code duplication have to avoid aggregation of any additional instance of Base class (duplication) Is it possible to reach these goals?

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• Java: Typecasting to Generics

  - by bguiz

  This method that uses method-level generics, that parses the values from a custom POJO, JXlistOfKeyValuePairs (which is exactly that). The only thing is that both the keys and values in JXlistOfKeyValuePairs are Strings. This method wants to taken in, in addition to the JXlistOfKeyValuePairs instance, a Class<T> that defines which data type to convert the values to (assume that only Boolean, Integer and Float are possible). It then outputs a HashMap with the specified type for the values in its entries. This is the code that I have got, and it is obviously broken. private <T extends Object> Map<String, T> fromListOfKeyValuePairs(JXlistOfKeyValuePairs jxval, Class<T> clasz) { Map<String, T> val = new HashMap<String, T>(); List<Entry> jxents = jxval.getEntry(); T value; String str; for (Entry jxent : jxents) { str = jxent.getValue(); value = null; if (clasz.isAssignableFrom(Boolean.class)) { value = (T)(Boolean.parseBoolean(str)); } else if (clasz.isAssignableFrom(Integer.class)) { value = (T)(Integer.parseInt(str)); } else if (clasz.isAssignableFrom(Float.class)) { value = (T)(Float.parseFloat(str)); } else { logger.warn("Unsupported value type encountered in key-value pairs, continuing anyway: " + clasz.getName()); } val.put(jxent.getKey(), value); } return val; } This is the bit that I want to solve: if (clasz.isAssignableFrom(Boolean.class)) { value = (T)(Boolean.parseBoolean(str)); } else if (clasz.isAssignableFrom(Integer.class)) { value = (T)(Integer.parseInt(str)); } I get: Inconvertible types required: T found: Boolean Also, if possible, I would like to be able to do this with more elegant code, avoiding Class#isAssignableFrom. Any suggestions? Sample method invocation: Map<String, Boolean> foo = fromListOfKeyValuePairs(bar, Boolean.class);

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• Can grub handle same release (3.6) but new rc (rc5)?

  - by hhoyt

  can grub handle newer kerner rc ? I am running 3.6.0-rc4 ok, grub update definitely recognizes all required files for rc5, but edit of grub.cfg only shows rc4 after grub-update. D/N matter whether I generate kernel 3.6.0-rc5 or whether I install the .deb files. Generating grub.cfg ... using custom appearance settings Found background image: /usr/share/peppermint/wallpapers/Peppermint.jpg Found linux image: /boot/vmlinuz-3.6.0-030600rc5-generic Found linux image: /boot/vmlinuz-3.6.0-030600rc4-generic Found initrd image: /boot/initrd.img-3.6.0-030600rc4-generic Found linux image: /boot/vmlinuz-3.6.0-rc5 Found initrd image: /boot/initrd.img-3.6.0-rc5 Found linux image: /boot/vmlinuz-3.6.0-rc5.old Found initrd image: /boot/initrd.img-3.6.0-rc5 Found linux image: /boot/vmlinuz-3.5.3 Found initrd image: /boot/initrd.img-3.5.3 Found linux image: /boot/vmlinuz-3.5.3.old Found initrd image: /boot/initrd.img-3.5.3 Found linux image: /boot/vmlinuz-3.5.0-13-generic Found initrd image: /boot/initrd.img-3.5.0-13-generic Found Ubuntu 10.04.1 LTS (10.04) on /dev/sda1 Found Ubuntu 10.04.4 LTS (10.04) on /dev/sda10 Found Peppermint Two (2) on /dev/sda15 Found Ubuntu 10.10 (10.10) on /dev/sda16 Found Windows 7 (loader) on /dev/sda3 Found Ubuntu 11.04 (11.04) on /dev/sda5 Found Ubuntu 12.04.1 LTS (12.04) on /dev/sda6 Found Linux Mint 12 LXDE (12) on /dev/sda8 Found MS-DOS 5.x/6.x/Win3.1 on /dev/sdc1 If I press 'e' on boot startup of rc4 and manually change it to rc5 and ctrl-x, it comes up fine. I just cannot get grub.cfg to update such that rc4 is included. Thanks, Howard # DO NOT EDIT THIS FILE # It is automatically generated by grub-mkconfig using templates from /etc/grub.d and settings from /etc/default/grub # BEGIN /etc/grub.d/00_header if [ -s $prefix/grubenv ]; then set have_grubenv=true load_env fi set default="Windows 7 (loader) (on /dev/sda3)" if [ "${prev_saved_entry}" ]; then set saved_entry="${prev_saved_entry}" save_env saved_entry set prev_saved_entry= save_env prev_saved_entry set boot_once=true fi function savedefault { if [ -z "${boot_once}" ]; then saved_entry="${chosen}" save_env saved_entry fi } function recordfail { set recordfail=1 if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi } function load_video { insmod vbe insmod vga insmod video_bochs insmod video_cirrus } insmod part_msdos insmod ext2 set root='(hd1,msdos1)' search --no-floppy --fs-uuid --set=root 218e9f6f-c21e-4c50-90a5-5a40be639b66 if loadfont /usr/share/grub/unicode.pf2 ; then set gfxmode=640x480 load_video insmod gfxterm insmod part_msdos insmod ext2 set root='(hd1,msdos1)' search --no-floppy --fs-uuid --set=root 218e9f6f-c21e-4c50-90a5-5a40be639b66 set locale_dir=($root)/boot/grub/locale set lang=en_US insmod gettext fi terminal_output gfxterm if [ "${recordfail}" = 1 ]; then set timeout=-1 else set timeout=10 fi END /etc/grub.d/00_header BEGIN /etc/grub.d/05_debian_theme insmod part_msdos insmod ext2 set root='(hd1,msdos1)' search --no-floppy --fs-uuid --set=root 218e9f6f-c21e-4c50-90a5-5a40be639b66 insmod jpeg if background_image /usr/share/peppermint/wallpapers/Peppermint.jpg; then set color_normal=light-gray/black set color_highlight=magenta/black else set menu_color_normal=white/black set menu_color_highlight=black/light-gray fi END /etc/grub.d/05_debian_theme BEGIN /etc/grub.d/10_linux_proxy menuentry "Peppermint, with Linux 3.6.0-030600rc4-generic" --class peppermint --class gnu-linux --class gnu --class os { recordfail insmod gzio insmod part_msdos insmod ext2 set root='(hd1,msdos1)' search --no-floppy --fs-uuid --set=root 218e9f6f-c21e-4c50-90a5-5a40be639b66 linux /boot/vmlinuz-3.6.0-030600rc4-generic root=UUID=218e9f6f-c21e-4c50-90a5-5a40be639b66 ro initrd /boot/initrd.img-3.6.0-030600rc4-generic } END /etc/grub.d/10_linux_proxy BEGIN /etc/grub.d/30_os-prober_proxy menuentry "Peppermint, with Linux 3.6.0-030600rc4-generic (on /dev/sda15)" --class gnu-linux --class gnu --class os { insmod part_msdos insmod ext2 set root='(hd0,msdos15)' search --no-floppy --fs-uuid --set=root 21a3d91a-ae43-4f51-b8d6-7f3dc80967d7 linux /boot/vmlinuz-3.6.0-030600rc4-generic root=UUID=21a3d91a-ae43-4f51-b8d6-7f3dc80967d7 ro splash quiet splash vt.handoff=7 initrd /boot/initrd.img-3.6.0-030600rc4-generic } menuentry "Ubuntu, with Linux 3.0.0-24-generic (on /dev/sda10)" --class gnu-linux --class gnu --class os { insmod part_msdos insmod ext2 set root='(hd0,msdos10)' search --no-floppy --fs-uuid --set=root 6c9a0149-3045-4335-83fa-a2513ca3a250 linux /boot/vmlinuz-3.0.0-24-generic root=UUID=6c9a0149-3045-4335-83fa-a2513ca3a250 ro crashkernel=384M-2G:64M,2G-:128M splash initrd /boot/initrd.img-3.0.0-24-generic } menuentry "Ubuntu, with Linux 3.5.0-030500rc7-generic (on /dev/sda10)" --class gnu-linux --class gnu --class os { insmod part_msdos insmod ext2 set root='(hd0,msdos10)' search --no-floppy --fs-uuid --set=root 6c9a0149-3045-4335-83fa-a2513ca3a250 linux /boot/vmlinuz-3.5.0-030500rc7-generic root=UUID=6c9a0149-3045-4335-83fa-a2513ca3a250 ro crashkernel=384M-2G:64M,2G-:128M splash initrd /boot/initrd.img-3.5.0-030500rc7-generic } menuentry "Peppermint, with Linux 3.3.0-030300rc2-generic (on /dev/sda15)" --class gnu-linux --class gnu --class os { insmod part_msdos insmod ext2 set root='(hd0,msdos15)' search --no-floppy --fs-uuid --set=root 21a3d91a-ae43-4f51-b8d6-7f3dc80967d7 linux /boot/vmlinuz-3.3.0-030300rc2-generic root=UUID=21a3d91a-ae43-4f51-b8d6-7f3dc80967d7 ro splash quiet splash vt.handoff=7 initrd /boot/initrd.img-3.3.0-030300rc2-generic } menuentry "Ubuntu, with Linux 2.6.39-rc5-candela (on /dev/sda16)" --class gnu-linux --class gnu --class os { insmod part_msdos insmod ext2 set root='(hd0,msdos16)' search --no-floppy --fs-uuid --set=root 48fcb5ec-b51b-4afd-b0e5-a2aace66f6e1 linux /boot/vmlinuz-2.6.39-rc5-candela root=/dev/sda7 ro splash initrd /boot/initrd.img-2.6.39-rc5-candela } menuentry "Windows 7 (loader) (on /dev/sda3)" --class windows --class os { insmod part_msdos insmod ntfs set root='(hd0,msdos3)' search --no-floppy --fs-uuid --set=root EA3EFABB3EFA7FBD chainloader +1 } menuentry "Ubuntu, with Linux 2.6.38-13-generic (on /dev/sda5)" --class gnu-linux --class gnu --class os { insmod part_msdos insmod ext2 set root='(hd0,msdos5)' search --no-floppy --fs-uuid --set=root bcfe855e-a449-429d-b204-c667e129a4bd linux /boot/vmlinuz-2.6.38-13-generic root=UUID=bcfe855e-a449-429d-b204-c667e129a4bd ro quiet splash vt.handoff=7 initrd /boot/initrd.img-2.6.38-13-generic } menuentry "Ubuntu, with Linux 3.2.0-29-generic-pae (on /dev/sda6)" --class gnu-linux --class gnu --class os { insmod part_msdos insmod ext2 set root='(hd0,msdos6)' search --no-floppy --fs-uuid --set=root 369605ad-1a92-4b7d-abb5-ce75cbdfc9c1 linux /boot/vmlinuz-3.2.0-29-generic-pae root=UUID=369605ad-1a92-4b7d-abb5-ce75cbdfc9c1 ro quiet splash $vt_handoff initrd /boot/initrd.img-3.2.0-29-generic-pae } menuentry "Ubuntu, with Linux 3.2.0-23-generic-pae (on /dev/sda6)" --class gnu-linux --class gnu --class os { insmod part_msdos insmod ext2 set root='(hd0,msdos6)' search --no-floppy --fs-uuid --set=root 369605ad-1a92-4b7d-abb5-ce75cbdfc9c1 linux /boot/vmlinuz-3.2.0-23-generic-pae root=UUID=369605ad-1a92-4b7d-abb5-ce75cbdfc9c1 ro quiet splash $vt_handoff initrd /boot/initrd.img-3.2.0-23-generic-pae } menuentry "Linux Mint 12 LXDE, 3.0.0-12-generic (/dev/sda8) (on /dev/sda8)" --class gnu-linux --class gnu --class os { insmod part_msdos insmod ext2 set root='(hd0,msdos8)' search --no-floppy --fs-uuid --set=root ccdc67ed-e81c-4f85-9b75-fe0c24c65bb8 linux /boot/vmlinuz-3.0.0-12-generic root=UUID=ccdc67ed-e81c-4f85-9b75-fe0c24c65bb8 ro quiet splash vt.handoff=7 initrd /boot/initrd.img-3.0.0-12-generic } menuentry "MS-DOS 5.x/6.x/Win3.1 (on /dev/sdc1)" --class windows --class os { insmod part_msdos insmod ntfs set root='(hd2,msdos1)' search --no-floppy --fs-uuid --set=root A8F0DE02F0DDD6A2 drivemap -s (hd0) ${root} chainloader +1 } END /etc/grub.d/30_os-prober_proxy BEGIN /etc/grub.d/40_custom This file provides an easy way to add custom menu entries. Simply type the menu entries you want to add after this comment. Be careful not to change the 'exec tail' line above. END /etc/grub.d/40_custom BEGIN /etc/grub.d/41_custom if [ -f $prefix/custom.cfg ]; then source $prefix/custom.cfg; fi END /etc/grub.d/41_custom

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• Generic Aggregation of C++ Objects by Attribute When Attribute Name is Unknown at Runtime

  - by stretch

  I'm currently implementing a system with a number of class's representing objects such as client, business, product etc. Standard business logic. As one might expect each class has a number of standard attributes. I have a long list of essentially identical requirements such as: the ability to retrieve all business' whose industry is manufacturing. the ability to retrieve all clients based in London Class business has attribute sector and client has attribute location. Clearly this a relational problem and in pseudo SQL would look something like: SELECT ALL business in business' WHERE sector == manufacturing Unfortunately plugging into a DB is not an option. What I want to do is have a single generic aggregation function whose signature would take the form: vector<generic> genericAggregation(class, attribute, value); Where class is the class of object I want to aggregate, attribute and value being the class attribute and value of interest. In my example I've put vector as return type, but this wouldn't work. Probably better to declare a vector of relevant class type and pass it as an argument. But this isn't the main problem. How can I accept arguments in string form for class, attribute and value and then map these in a generic object aggregation function? Since it's rude not to post code, below is a dummy program which creates a bunch of objects of imaginatively named classes. Included is a specific aggregation function which returns a vector of B objects whose A object is equal to an id specified at the command line e.g. .. $ ./aggregations 5 which returns all B's whose A objects 'i' attribute is equal to 5. See below: #include <iostream> #include <cstring> #include <sstream> #include <vector> using namespace std; //First imaginativly names dummy class class A { private: int i; double d; string s; public: A(){} A(int i, double d, string s) { this->i = i; this->d = d; this->s = s; } ~A(){} int getInt() {return i;} double getDouble() {return d;} string getString() {return s;} }; //second imaginativly named dummy class class B { private: int i; double d; string s; A *a; public: B(int i, double d, string s, A *a) { this->i = i; this->d = d; this->s = s; this->a = a; } ~B(){} int getInt() {return i;} double getDouble() {return d;} string getString() {return s;} A* getA() {return a;} }; //Containers for dummy class objects vector<A> a_vec (10); vector<B> b_vec;//100 //Util function, not important.. string int2string(int number) { stringstream ss; ss << number; return ss.str(); } //Example function that returns a new vector containing on B objects //whose A object i attribute is equal to 'id' vector<B> getBbyA(int id) { vector<B> result; for(int i = 0; i < b_vec.size(); i++) { if(b_vec.at(i).getA()->getInt() == id) { result.push_back(b_vec.at(i)); } } return result; } int main(int argc, char** argv) { //Create some A's and B's, each B has an A... //Each of the 10 A's are associated with 10 B's. for(int i = 0; i < 10; ++i) { A a(i, (double)i, int2string(i)); a_vec.at(i) = a; for(int j = 0; j < 10; j++) { B b((i * 10) + j, (double)j, int2string(i), &a_vec.at(i)); b_vec.push_back(b); } } //Got some objects so lets do some aggregation //Call example aggregation function to return all B objects //whose A object has i attribute equal to argv[1] vector<B> result = getBbyA(atoi(argv[1])); //If some B's were found print them, else don't... if(result.size() != 0) { for(int i = 0; i < result.size(); i++) { cout << result.at(i).getInt() << " " << result.at(i).getA()->getInt() << endl; } } else { cout << "No B's had A's with attribute i equal to " << argv[1] << endl; } return 0; } Compile with: g++ -o aggregations aggregations.cpp If you wish :) Instead of implementing a separate aggregation function (i.e. getBbyA() in the example) I'd like to have a single generic aggregation function which accounts for all possible class attribute pairs such that all aggregation requirements are met.. and in the event additional attributes are added later, or additional aggregation requirements, these will automatically be accounted for. So there's a few issues here but the main one I'm seeking insight into is how to map a runtime argument to a class attribute. I hope I've provided enough detail to adequately describe what I'm trying to do...

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• C#/.NET Fundamentals: Choosing the Right Collection Class

  - by James Michael Hare

  The .NET Base Class Library (BCL) has a wide array of collection classes at your disposal which make it easy to manage collections of objects. While it's great to have so many classes available, it can be daunting to choose the right collection to use for any given situation. As hard as it may be, choosing the right collection can be absolutely key to the performance and maintainability of your application! This post will look at breaking down any confusion between each collection and the situations in which they excel. We will be spending most of our time looking at the System.Collections.Generic namespace, which is the recommended set of collections. The Generic Collections: System.Collections.Generic namespace The generic collections were introduced in .NET 2.0 in the System.Collections.Generic namespace. This is the main body of collections you should tend to focus on first, as they will tend to suit 99% of your needs right up front. It is important to note that the generic collections are unsynchronized. This decision was made for performance reasons because depending on how you are using the collections its completely possible that synchronization may not be required or may be needed on a higher level than simple method-level synchronization. Furthermore, concurrent read access (all writes done at beginning and never again) is always safe, but for concurrent mixed access you should either synchronize the collection or use one of the concurrent collections. So let's look at each of the collections in turn and its various pros and cons, at the end we'll summarize with a table to help make it easier to compare and contrast the different collections. The Associative Collection Classes Associative collections store a value in the collection by providing a key that is used to add/remove/lookup the item. Hence, the container associates the value with the key. These collections are most useful when you need to lookup/manipulate a collection using a key value. For example, if you wanted to look up an order in a collection of orders by an order id, you might have an associative collection where they key is the order id and the value is the order. The Dictionary<TKey,TVale> is probably the most used associative container class. The Dictionary<TKey,TValue> is the fastest class for associative lookups/inserts/deletes because it uses a hash table under the covers. Because the keys are hashed, the key type should correctly implement GetHashCode() and Equals() appropriately or you should provide an external IEqualityComparer to the dictionary on construction. The insert/delete/lookup time of items in the dictionary is amortized constant time - O(1) - which means no matter how big the dictionary gets, the time it takes to find something remains relatively constant. This is highly desirable for high-speed lookups. The only downside is that the dictionary, by nature of using a hash table, is unordered, so you cannot easily traverse the items in a Dictionary in order. The SortedDictionary<TKey,TValue> is similar to the Dictionary<TKey,TValue> in usage but very different in implementation. The SortedDictionary<TKey,TValye> uses a binary tree under the covers to maintain the items in order by the key. As a consequence of sorting, the type used for the key must correctly implement IComparable<TKey> so that the keys can be correctly sorted. The sorted dictionary trades a little bit of lookup time for the ability to maintain the items in order, thus insert/delete/lookup times in a sorted dictionary are logarithmic - O(log n). Generally speaking, with logarithmic time, you can double the size of the collection and it only has to perform one extra comparison to find the item. Use the SortedDictionary<TKey,TValue> when you want fast lookups but also want to be able to maintain the collection in order by the key. The SortedList<TKey,TValue> is the other ordered associative container class in the generic containers. Once again SortedList<TKey,TValue>, like SortedDictionary<TKey,TValue>, uses a key to sort key-value pairs. Unlike SortedDictionary, however, items in a SortedList are stored as an ordered array of items. This means that insertions and deletions are linear - O(n) - because deleting or adding an item may involve shifting all items up or down in the list. Lookup time, however is O(log n) because the SortedList can use a binary search to find any item in the list by its key. So why would you ever want to do this? Well, the answer is that if you are going to load the SortedList up-front, the insertions will be slower, but because array indexing is faster than following object links, lookups are marginally faster than a SortedDictionary. Once again I'd use this in situations where you want fast lookups and want to maintain the collection in order by the key, and where insertions and deletions are rare. The Non-Associative Containers The other container classes are non-associative. They don't use keys to manipulate the collection but rely on the object itself being stored or some other means (such as index) to manipulate the collection. The List<T> is a basic contiguous storage container. Some people may call this a vector or dynamic array. Essentially it is an array of items that grow once its current capacity is exceeded. Because the items are stored contiguously as an array, you can access items in the List<T> by index very quickly. However inserting and removing in the beginning or middle of the List<T> are very costly because you must shift all the items up or down as you delete or insert respectively. However, adding and removing at the end of a List<T> is an amortized constant operation - O(1). Typically List<T> is the standard go-to collection when you don't have any other constraints, and typically we favor a List<T> even over arrays unless we are sure the size will remain absolutely fixed. The LinkedList<T> is a basic implementation of a doubly-linked list. This means that you can add or remove items in the middle of a linked list very quickly (because there's no items to move up or down in contiguous memory), but you also lose the ability to index items by position quickly. Most of the time we tend to favor List<T> over LinkedList<T> unless you are doing a lot of adding and removing from the collection, in which case a LinkedList<T> may make more sense. The HashSet<T> is an unordered collection of unique items. This means that the collection cannot have duplicates and no order is maintained. Logically, this is very similar to having a Dictionary<TKey,TValue> where the TKey and TValue both refer to the same object. This collection is very useful for maintaining a collection of items you wish to check membership against. For example, if you receive an order for a given vendor code, you may want to check to make sure the vendor code belongs to the set of vendor codes you handle. In these cases a HashSet<T> is useful for super-quick lookups where order is not important. Once again, like in Dictionary, the type T should have a valid implementation of GetHashCode() and Equals(), or you should provide an appropriate IEqualityComparer<T> to the HashSet<T> on construction. The SortedSet<T> is to HashSet<T> what the SortedDictionary<TKey,TValue> is to Dictionary<TKey,TValue>. That is, the SortedSet<T> is a binary tree where the key and value are the same object. This once again means that adding/removing/lookups are logarithmic - O(log n) - but you gain the ability to iterate over the items in order. For this collection to be effective, type T must implement IComparable<T> or you need to supply an external IComparer<T>. Finally, the Stack<T> and Queue<T> are two very specific collections that allow you to handle a sequential collection of objects in very specific ways. The Stack<T> is a last-in-first-out (LIFO) container where items are added and removed from the top of the stack. Typically this is useful in situations where you want to stack actions and then be able to undo those actions in reverse order as needed. The Queue<T> on the other hand is a first-in-first-out container which adds items at the end of the queue and removes items from the front. This is useful for situations where you need to process items in the order in which they came, such as a print spooler or waiting lines. So that's the basic collections. Let's summarize what we've learned in a quick reference table.  Collection Ordered? Contiguous Storage? Direct Access? Lookup Efficiency Manipulate Efficiency Notes Dictionary No Yes Via Key Key: O(1) O(1) Best for high performance lookups. SortedDictionary Yes No Via Key Key: O(log n) O(log n) Compromise of Dictionary speed and ordering, uses binary search tree. SortedList Yes Yes Via Key Key: O(log n) O(n) Very similar to SortedDictionary, except tree is implemented in an array, so has faster lookup on preloaded data, but slower loads. List No Yes Via Index Index: O(1) Value: O(n) O(n) Best for smaller lists where direct access required and no ordering. LinkedList No No No Value: O(n) O(1) Best for lists where inserting/deleting in middle is common and no direct access required. HashSet No Yes Via Key Key: O(1) O(1) Unique unordered collection, like a Dictionary except key and value are same object. SortedSet Yes No Via Key Key: O(log n) O(log n) Unique ordered collection, like SortedDictionary except key and value are same object. Stack No Yes Only Top Top: O(1) O(1)* Essentially same as List<T> except only process as LIFO Queue No Yes Only Front Front: O(1) O(1) Essentially same as List<T> except only process as FIFO   The Original Collections: System.Collections namespace The original collection classes are largely considered deprecated by developers and by Microsoft itself. In fact they indicate that for the most part you should always favor the generic or concurrent collections, and only use the original collections when you are dealing with legacy .NET code. Because these collections are out of vogue, let's just briefly mention the original collection and their generic equivalents: ArrayList A dynamic, contiguous collection of objects. Favor the generic collection List<T> instead. Hashtable Associative, unordered collection of key-value pairs of objects. Favor the generic collection Dictionary<TKey,TValue> instead. Queue First-in-first-out (FIFO) collection of objects. Favor the generic collection Queue<T> instead. SortedList Associative, ordered collection of key-value pairs of objects. Favor the generic collection SortedList<T> instead. Stack Last-in-first-out (LIFO) collection of objects. Favor the generic collection Stack<T> instead. In general, the older collections are non-type-safe and in some cases less performant than their generic counterparts. Once again, the only reason you should fall back on these older collections is for backward compatibility with legacy code and libraries only. The Concurrent Collections: System.Collections.Concurrent namespace The concurrent collections are new as of .NET 4.0 and are included in the System.Collections.Concurrent namespace. These collections are optimized for use in situations where multi-threaded read and write access of a collection is desired. The concurrent queue, stack, and dictionary work much as you'd expect. The bag and blocking collection are more unique. Below is the summary of each with a link to a blog post I did on each of them. ConcurrentQueue Thread-safe version of a queue (FIFO). For more information see: C#/.NET Little Wonders: The ConcurrentStack and ConcurrentQueue ConcurrentStack Thread-safe version of a stack (LIFO). For more information see: C#/.NET Little Wonders: The ConcurrentStack and ConcurrentQueue ConcurrentBag Thread-safe unordered collection of objects. Optimized for situations where a thread may be bother reader and writer. For more information see: C#/.NET Little Wonders: The ConcurrentBag and BlockingCollection ConcurrentDictionary Thread-safe version of a dictionary. Optimized for multiple readers (allows multiple readers under same lock). For more information see C#/.NET Little Wonders: The ConcurrentDictionary BlockingCollection Wrapper collection that implement producers & consumers paradigm. Readers can block until items are available to read. Writers can block until space is available to write (if bounded). For more information see C#/.NET Little Wonders: The ConcurrentBag and BlockingCollection Summary The .NET BCL has lots of collections built in to help you store and manipulate collections of data. Understanding how these collections work and knowing in which situations each container is best is one of the key skills necessary to build more performant code. Choosing the wrong collection for the job can make your code much slower or even harder to maintain if you choose one that doesn’t perform as well or otherwise doesn’t exactly fit the situation. Remember to avoid the original collections and stick with the generic collections.  If you need concurrent access, you can use the generic collections if the data is read-only, or consider the concurrent collections for mixed-access if you are running on .NET 4.0 or higher.   Tweet Technorati Tags: C#,.NET,Collecitons,Generic,Concurrent,Dictionary,List,Stack,Queue,SortedList,SortedDictionary,HashSet,SortedSet

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• Class Design - Returning a List<Object> From <Object>

  - by Mike

  Given a simple class: public class Person { public string FirstName; public string LastName; public string GetFullName() { return FirstName + LastName; } } The user of this class will populate a List<Person> object by reading an Xml file or some other data source. Should the logic for populating the List be in the Person class or should it just remain in the calling class? In other words, should there be a public List<Persons> GetPersons() method in the Person class or in the calling class? Or should the data accessor be in another class altogether? I know this is a rather simplistic question but I'm just curious how others typically do it.

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