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  • Extending a singleton class

    - by cakyus
    i used to create an instance of a singleton class like this: $Singleton = SingletonClassName::GetInstance(); and for non singleton class: $NonSingleton = new NonSingletonClassName; i think we should not differentiate how we create an instance of a class whether this is a singleton or not. if i look in perception of other class, i don't care whether the class we need a singleton class or not. so, i still not comfortable with how php treat a singleton class. i think and i always want to write: $Singleton = new SingletonClassName; just another non singleton class, is there a solution to this problem ?

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  • Handling empty UITableView in UITableViewController

    - by Travis
    I have a UITableViewController that is populated with some data. If the data comes back empty, obviously the table is empty. What is the appropriate method to use to handle this case and put up something like a UILabel with "No Data Available". I have been using - (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section but it's proven a bit cumbersome and I'm not longer confident it's the best place to do this.

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  • Setting nested object to null when combobox has empty value

    - by Javi
    Hello, I have a Class which models a User and another which models his country. Something like this: public class User{ private Country country; //other attributes and getter/setters } public class Country{ private Integer id; private String name; //other attributes and getter/setters } I have a Spring form where I have a combobox so the user can select his country or can select the undefined option to indicate he doen't want to provide this information. So I have something like this: <form:select path="country"> <form:option value="">-Select one-</form:option> <form:options items="${countries}" itemLabel="name" itemValue="id"/> </form:select> In my controller I get the autopopulated object with the user information and I want to have country set to null when the "-Select one-" option has been selected. So I have set a initBinder with a custom editor like this: @InitBinder protected void initBinder(WebDataBinder binder) throws ServletException { binder.registerCustomEditor(Country.class, "country", new CustomCountryEditor()); } and my editor do something like this: public class CustomCountryEditor(){ @Override public String getAsText() { //I return the Id of the country } @Override public void setAsText(String str) { //I search in the database for a country with id = new Integer(str) //and set country to that value //or I set country to null in case str == null } } When I submit the form it works because when I have country set to null when I have selected "-Select one-" option or the instance of the country selected. The problem is that when I load the form I have a method like the following one to load the user information. @ModelAttribute("user") public User getUser(){ //loads user from database } The object I get from getUser() has country set to a specific country (not a null value), but in the combobox is not selected any option. I've debugged the application and the CustomCountryEditor works good when setting and getting the text, thoughgetAsText method is called for every item in the list "countries" not only for the "country" field. Any idea? Is there a better way to set null the country object when I select no country option in the combobox? Thanks

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  • C# - Determine if class initializaion causes infinite recursion?

    - by John M
    I am working on porting a VB6 application to C# (Winforms 3.5) and while doing so I'm trying to break up the functionality into various classes (ie database class, data validation class, string manipulation class). Right now when I attempt to run the program in Debug mode the program pauses and then crashes with a StackOverFlowException. VS 2008 suggests a infinite recursion cause. I have been trying to trace what might be causing this recursion and right now my only hypothesis is that class initializations (which I do in the header(?) of each class). My thought is this: mainForm initializes classA classA initializes classB classB initializes classA .... Does this make sense or should I be looking elsewhere? UPDATE1 (a code sample): mainForm namespace john { public partial class frmLogin : Form { stringCustom sc = new sc(); stringCustom namespace john { class stringCustom { retrieveValues rv = new retrieveValues(); retrieveValues namespace john { class retrieveValues { stringCustom sc = new stringCustom();

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  • Inheritance of Custom Attributes on Abstract Properties

    - by Marty Trenouth
    I've got a custom attribute that I want to apply to my base abstract class so that I can skip elements that don't need to be viewed by the user when displaying the item in HTML. It seems that the properties overriding the base class are not inheriting the attributes. Does overriding base properties (abstract or virtual) blow away attributes placed on the original property? From Attribute class Defination [AttributeUsage(AttributeTargets.Property, Inherited = true, AllowMultiple = false)] public class NoHtmlOutput : Attribute { } From Abstract Class Defination [NoHtmlOutput] public abstract Guid UniqueID { get; set; } From Concrete Class Defination public override Guid UniqueID{ get{ return MasterId;} set{MasterId = value;}} From class checking for attribute Type t = o.GetType(); foreach (PropertyInfo pi in t.GetProperties()) { if (pi.GetCustomAttributes(typeof(NoHtmlOutput), true).Length == 1) continue; // processing logic goes here }

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  • Why is Collection<String>.class Illegal?

    - by Peter
    I am puzzled by generics. You can declare a field like: Class<Collection<String>> clazz = ... It seems logical that you could assign this field with: Class<Collection<String>> clazz = Collection<String>.class; However, this generates an error: Syntax error on token ">", void expected after this token So it looks like the .class operator does not work with generics. So I tried: class A<S> {} class B extends A<String> {} Class<A<String>> c = B.class; Also does not work, generates: Type mismatch: cannot convert from Class<Test.StringCollection> to Class<Collection<String>> Now, I really fail to see why this should not work. I know generic types are not reified but in both cases it seems to be fully type safe without having access to runtime generic types. Anybody an idea? Peter Kriens

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  • jquery to check if returned data object is empty

    - by user253530
    $("#post").live("click",function() { $("input:checkbox[name='bookmarkid']:checked").each(function() { $.post("php/socialbookmark-post.php", {bookmarkID: $(this).val()},function(data) { if(data != "") alert(data); }); }); }); the php file outputs some text only if something goes wrong. The checking that I do fails if the data is empty and displays an empty message. I need to fix this. Any ideas?

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  • Java: why does extending need an empty constructor?

    - by HH
    I have classes SearchToUser and getFilesToWord. GetFilesToWord must inherit SearchToUser fields. Extending works if an empty construction in SearchToUser-class, otherwise: cannot find symbol symbol : constructor SearchToUser() location: class SearchToUser public class GetFilesToWord extends SearchToUser{ ^ 1 error make: *** [all] Error 1 I cannot understand why the empty constructor is required for extending.

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  • characteristics of the abstract class

    - by Harsha
    Hello All, I like to know what makes a class to be called as absract class. I believe, abract key word definetly make a class class, but if one takes out the keyword, then we can create the instance of the class. In otherwords, what are the characteristics of the abstract class. Thanks in advance. -Harsha

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  • Setting nested object to null when selected option has empty value

    - by Javi
    Hello, I have a Class which models a User and another which models his country. Something like this: public class User{ private Country country; //other attributes and getter/setters } public class Country{ private Integer id; private String name; //other attributes and getter/setters } I have a Spring form where I have a combobox so the user can select his country or can select the undefined option to indicate he doen't want to provide this information. So I have something like this: <form:select path="country"> <form:option value="">-Select one-</form:option> <form:options items="${countries}" itemLabel="name" itemValue="id"/> </form:select> In my controller I get the autopopulated object with the user information and I want to have country set to null when the "-Select one-" option has been selected. So I have set a initBinder with a custom editor like this: @InitBinder protected void initBinder(WebDataBinder binder) throws ServletException { binder.registerCustomEditor(Country.class, "country", new CustomCountryEditor()); } and my editor do something like this: public class CustomCountryEditor(){ @Override public String getAsText() { //I return the Id of the country } @Override public void setAsText(String str) { //I search in the database for a country with id = new Integer(str) //and set country to that value //or I set country to null in case str == null } } When I submit the form it works because when I have country set to null when I have selected "-Select one-" option or the instance of the country selected. The problem is that when I load the form I have a method like the following one to load the user information. @ModelAttribute("user") public User getUser(){ //loads user from database } The object I get from getUser() has country set to a specific country (not a null value), but in the combobox is not selected any option. I've debugged the application and the CustomCountryEditor works good when setting and getting the text, thoughgetAsText method is called for every item in the list "countries" not only for the "country" field. Any idea? Is there a better way to set null the country object when I select no country option in the combobox? Thanks

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  • Binding functions of derived class with luabind

    - by Anamon
    I am currently developing a plugin-based system in C++ which provides a Lua scripting interface, for which I chose to use luabind. I'm using Lua 5 and luabind 0.9, both statically linked and compiled with MSVC++ 8. I am now having trouble binding functions with luabind when they are defined in a derived class, but not its parent class. More specifically, I have an abstract base class called 'IPlugin' from which all plugin classes inherit. When the plugin manager initialises, it registers that class and its functions like this: luabind::open(L); luabind::module(L) [ luabind::class_("IPlugin") .def("start", (void(IPlugin::*)())&IPlugin::start) ]; As it is only known at runtime what effective plugin classes are available, I had to solve loading plugins in a kind of roundabout way. The plugin manager exposes a factory function to Lua, which takes the name of a plugin class and a desired object name. The factory then creates the object, registers the plugin's class as inheriting from the 'IPlugin' base class, and immediately calls a function on the created object that registers itself as a global with the Lua state, like this: void PluginExample::registerLuaObject(lua_State *L, string a_name) { luabind::globals(L)[a_name] = (PluginExample*)this; } I initially did this because I had problems with Lua determining the most derived class of the object, as if I register it from the StreamManager it is only known as a subtype of 'IPlugin' and not the specific subtype. I'm not sure anymore if this is even necessary though, but it works and the created object is subsequently accessible from Lua under 'a_name'. The problem I have, though, is that functions defined in the derived class, which were not declared at all in the parent class, cannot be used. Virtual functions defined in the base class, such as 'start' above, work fine, and calling them from Lua on the new object runs the respective redefined code from the 'PluginExample' class. But if I add a new function to 'PluginExample', here for example a function taking no arguments and returning void, and register it like this: luabind::module(L) [ luabind::class_("PluginExample") .def(luabind::constructor()) .def("func", &PluginExample::func) ]; calling 'func' on the new object yields the following Lua runtime error: No matching overload found, candidates: void func(PluginExample&) I am correctly using the ':' syntax so the 'self' argument is not needed and it seems suddenly Lua cannot determine the derived type of the object anymore. I am sure I am doing something wrong, probably having to do with the two-step binding required by my system architecture, but I can't figure out where. I'd much appreciate some help =)

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  • How to "escape" the JavaScript class keyword to specify a CSS class value.

    - by Robert Claypool
    C# allows a reserved word to be used as a property name via the ampersand. e.g. // In ASP.NET MVC, we use @class to define // the css class attribute for some HtmlHelper methods. var htmlObject = new { readonly = "readonly", @class = "ui-state-highlight" } I want to do the same in JavaScript. e.g. function makeGrid(grid, pager) { grid.jqGrid({ caption: 'Configurations', colNames: ['Id', 'Name'], colModel: [ { name: 'Id', index: 'Id' }, { name: 'Name', index: 'Name', editable: true, editoptions: { readonly: 'readonly', class: 'FormElement readonly' } }, ], pager: pager, url: 'www.example.com/app/configurations") %>', editurl: 'www.example.com/app/configurations/edit") %>' }).navGrid(pager, { edit: true, add: false, del: false, search: false }, {}, {}, {}); } Note class: 'FormElement readonly' is supposed to set the css class value on jqGrid's edit dialog, but IE errors out on the reserved word. Is there an escape character in JavaScript too? #class? @class? &class? Otherwise, how might I tell jqGrid to set the css class on the popup editor? Thank you.

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  • Classification: Dealing with Abstain/Rejected Class

    - by abner.ayala
    I am asking for your input and/help on a classification problem. If anyone have any references that I can read to help me solve my problem even better. I have a classification problem of four discrete and very well separated classes. However my input is continuous and has a high frequency (50Hz), since its a real-time problem. The circles represent the clusters of the classes, the blue line the decision boundary and Class 5 equals the (neutral/resting do nothing class). This class is the rejected class. However the problem is that when I move from one class to the other I activate a lot of false positives in the transition movements, since the movement is clearly non-linear. For example, every time I move from class 5 (neutral class) to 1 I first see a lot of 3's before getting to the 1 class. Ideally, I will want my decision boundary to look like the one in the picture below where the rejected class is Class =5. Has a higher decision boundary than the others classes to avoid misclassification during transition. I am currently implementing my algorithm in Matlab using naive bayes, kNN, and SVMs optimized algorithms using Matlab. Question: What is the best/common way to handle abstain/rejected classes classes? Should I use (fuzzy logic, loss function, should I include resting cluster in the training)?

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  • Scala - Enumeration vs. Case-Classes

    - by tzofia
    I've created akka actor called LogActor. The LogActors's receive method handling messages from other actors and logging them to the specified log level. I can distinguish between the different levels in 2 ways. The first one: import LogLevel._ object LogLevel extends Enumeration { type LogLevel = Value val Error, Warning, Info, Debug = Value } case class LogMessage(level : LogLevel, msg : String) The second: (EDIT) abstract class LogMessage(msg : String) case class LogMessageError(msg : String) extends LogMessage(msg) case class LogMessageWarning(msg : String) extends LogMessage(msg) case class LogMessageInfo(msg : String) extends LogMessage(msg) case class LogMessageDebug(msg : String) extends LogMessage(msg) Which way is more efficient? does it take less time to match case class or to match enum value? (I read this question but there isn't any answer referring to the runtime issue)

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  • Passing Interface Class as a Parameter in Java

    - by aleclerc
    I have an interface: public interface IMech { } and a class that implements it public class Email implements IMech { } and a third class that has this method implemented: public void sendNotification( Class< IMech > mechanism ){ } now I'm trying to call that method like so foo.sendNotification(Email.class); but i keep getting an exception saying: The method sendNotification(Class<IMechanism>) in the type RemediationOperator is not applicable for the arguments (Class<EmailNotification>) Shouldn't this work if it interfaces that class?

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  • PHP Nested classes work... sort of?

    - by SeanJA
    So, if you try to do a nested class like this: //nestedtest.php class nestedTest{ function test(){ class E extends Exception{} throw new E; } } You will get an error Fatal error: Class declarations may not be nested in [...] but if you have a class in a separate file like so: //nestedtest2.php class nestedTest2{ function test(){ include('e.php'); throw new E; } } //e.php class E Extends Exception{} So, why does the second hacky way of doing it work, but the non-hacky way of doing it does not work?

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  • Singleton class issue in Qt

    - by sijith
    i created a singleton class and trying to access that class in other class but getting error "cannot access private member" Setupconfig is my singleton class and i am trying to access this class in other class which have QMainWindow Error 'Setupconfig::Setupconfig' : cannot access private member declared in class 'Setupconfig' ///////////////////////////////////////////////////////////////////// Setupconfig.h static Setupconfig *buiderObj() { static Setupconfig *_setupObj= new Setupconfig(); return _setupObj; } private: Setupconfig(); ////////////////////////////////////// EasyBudget.h class EasyBudget : public QMainWindow, public Ui::EasyBudgetClass, public Setupconfig { Q_OBJECT public: Setupconfig *setupObj; } ////////////////////////////////////// EasyBudget.cpp EasyBudget::EasyBudget(QWidget *parent, Qt::WFlags flags) : QMainWindow(parent,Qt::FramelessWindowHint) { setupObj=Setupconfig::buiderObj(); }

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