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  • C++ explicit template specialization of templated constructor of templated class

    - by Victor Liu
    I have a class like template <class T> struct A{ template <class U> A(U u); }; I would like to write an explicit specialization of this for a declaration like A<int>::A(float); In the following test code, if I comment out the specialization, it compiles with g++. Otherwise, it says I have the wrong number of template parameters: #include <iostream> template <class T> struct A{ template <class U> A(T t, U *u){ *u += U(t); } }; template <> template <> A<int>::A<int,float>(int t, float *u){ *u += U(2*t); } int main(){ float f = 0; int i = 1; A<int>(i, &f); std::cout << f << std::endl; return 0; }

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  • Sharing common class in wcf project

    - by Saint
    class MyCommonClass { //properties } This class should be accessible in service project wcf-client project the other for which they are references. In this common project I can't generate servicereferences. I think, I could don't generate MyCommonClass in ServiceReferences but how to mark class to be nonserializable? In properties there's IgnoreDataMemberAttribute. I tried also reuse MyCommonClass type located in common project, but it is still generated

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  • Why are my ActiveRecord class instance variables disappearing after the first request in development

    - by Paul C
    I have a class instance variable on one of my AR classes. I set its value at boot with an initializer and, after that, never touch it again except to read from it. In development mode, this value disappears after the first request to the web server. However, when running tests, using the console or running the production server this does not happen. # The AR class class Group < ActiveRecord::Base class << self attr_accessor :path end end # The initializer Group.path = File.join(RAILS_ROOT, "public", "etc") # First request in a view %p= Group.path #=> "/home/rails/app/public/etc" # Second request in a view %p= Group.path #=> nil Is there something about development mode that nukes instance variables from classes with each request? If so, is there a way to disable this for specific variables or classes?

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  • C# Pass Generics At Runtime

    - by TheCloudlessSky
    I have a method like the following: public IEnumerable<T> GetControls<T>() : where T : ControlBase { // removed. } I then created a class: public class HandleBase<TOwner> : ControlBase : TOwner { // Removed } I'd like to be able to call GetControls<HandleBase<this.GetType()>>; where it would use the type of THIS class to pass to the HandleBase. This would in essentially get all HandleBase that have an owner of THIS type. How can I achieve this?

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  • derived class as default argument g++

    - by Vincent
    Please take a look at this code: template<class T> class A { class base { }; class derived : public A<T>::base { }; public: int f(typename A<T>::base& arg = typename A<T>::derived()) { return 0; } }; int main() { A<int> a; a.f(); return 0; } Compiling generates the following error message in g++: test.cpp: In function 'int main()': test.cpp:25: error: default argument for parameter of type 'A<int>::base&' has type 'A<int>::derived' The basic idea (using derived class as default value for base-reference-type argument) works in visual studio, but not in g++. I have to publish my code to the university server where they compile it with gcc. What can I do? Is there something I am missing?

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  • How to dynamically set validation messages on properties with a class validation attribute

    - by Dan
    I'm writing Validation attribute that sits on the class but inspects the properties of the class. I want it to set a validation message on each of the properties it finds to be invalid. How do I do this? This is what I have got so far: [AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = true)] public class LinkedFieldValidationAttribute : ValidationAttribute { private readonly string[] _properiesToValidate; public LinkedFieldValidationAttribute(params string[] properiesToValidate) { _properiesToValidate = properiesToValidate; } public override bool IsValid(object value) { PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(value); foreach (var propertyName in _properiesToValidate) { var propertyValue = properties.Find(propertyName, false).GetValue(value); //if value is invalid add message from base } //return validity } }

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  • In what package should a "Settings" class be?

    - by Tom
    I've in the middle of building an application but found myself too easily creating new packages without keeping the project's structure in mind. Now, I'm trying to redo the whole project structure on paper first. I am using a Settings class with public properties, accessed as settings for several other classes around the project. Now, since this Settings class applies for the whole project, I am unsure if it should be packaged and if so, in what kind of package should it exist? Or should it be in the root (the default package) with the main application class? I've been thinking about putting it in my utils package, then again I don't think it really is an utlity. Any strategies on how to decide on such package structure for example for a Settings class?

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  • Change storyboard UIImageView to own class with backgroundcolor

    - by Thomas
    I want to draw the background image on my own, so I decided to implement a UIImageView class and connect it in the Storyboard. As first task I just want to set the backgroundcolor of the image on my own, but it's never shown. Image just stays blank. That's the class: class FirstBackgroundImage : UIImageView { required init(coder aDecoder: NSCoder) { super.init(coder: aDecoder) self.backgroundColor = UIColor.redColor() } override init() { super.init() self.backgroundColor = UIColor.redColor() } override required init(image: UIImage!) { super.init(image: image) self.backgroundColor = UIColor.redColor() } } That's how i connected it:

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  • Obtaining reference to Class instance by string name - VB.NET

    - by Jeff Williams
    Is it possible using Reflection or some other method to obtain a reference to a specific class instance from the name of that class instance? For example the framework for the applications i develop heavily uses public class instances such as: Public bMyreference as MyReference = new MyReference Then throughout the application bMyReference is used by custom controls and code. One of the properties of the custom controls is the "FieldName" which references a Property in these class instances (bMyReference.MyField) as a string. What i would like to be able to do is analyze this string "bMyReference.MyField" and then refer back to the actual Instance/Property. In VB6 I would use an EVAL or something simular to convert the string to an actual object but this obviously doesn't work in VB.net What I'm picturing is something like this Dim FieldName as String = MyControl.FieldName ' sets FielName to bMyReference.MyField Dim FieldObject() as String = FieldName.Split(".") ' Split into the Object / Property Dim myInstance as Object = ......... ' Obtain a reference to the Instance and set as myInstance Dim myProperty = myInstance.GetType().GetProperty(FieldObject(1))

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  • Appengine (python) returns empty for valid queries

    - by Grant
    I've got an app with around half a million 'records', each of which only stores three fields. I'd like to look up records by a string field with a query, but I'm running into problems. If I visit the console page, manually view a record and save it (without making changes) it shows up in a query: SELECT * FROM wordEntry WHERE wordStr = 'SomeString' If I don't do this, I get 'no results'. Does appengine need time to update? If so, how much? (I was also having trouble batch deleting and modifying data, but I was able to break the problem up into smaller chunks.)

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  • Java - Could not find the main class?

    - by asmo
    I'm having a hard-time with a Java error. I'm getting this when double-clicking on my compiled project Jar file in order to run it: Could not find the main class: testPackage.testFrame. Program will exit. However, my main class is cleary defined in the project properties. Furthermore, everything works fine when I run the project directly from NetBeans. I'm using the ip2c.jar third-party library to determine countries from IP addresses. If I comment the class that is using the ip2c.jar file, I don't get the error. How can a third-party library be preventing the JVM from finding my main class?

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  • How can i use 'log' inside a src/groovy/ class

    - by firnnauriel
    I'm encountering this error: groovy.lang.MissingPropertyException: No such property: log for class: org.utils.MyClass Here's the content of the class: package org.utils class MyClass { int organizationCount = 0 public int getOrganizationCount(){ log.debug "There are ${organizationCount} organization(s) found." return organizationCount } } Do i need to add an import statement? What do i need to add? Note that the class is located in src/groovy/org/utils. I know that the 'log' variable is accessible in controllers, services, etc. Not sure in 'src' classes. Thanks.

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  • Encapsulating user input of data for a class (C++)

    - by Dr. Monkey
    For an assignment I've made a simple C++ program that uses a superclass (Student) and two subclasses (CourseStudent and ResearchStudent) to store a list of students and print out their details, with different details shown for the two different types of students (using overriding of the display() method from Student). My question is about how the program collects input from the user of things like the student name, ID number, unit and fee information (for a course student) and research information (for research students): My implementation has the prompting for user input and the collecting of that input handled within the classes themselves. The reasoning behind this was that each class knows what kind of input it needs, so it makes sense to me to have it know how to ask for it (given an ostream through which to ask and an istream to collect the input from). My lecturer says that the prompting and input should all be handled in the main program, which seems to me somewhat messier, and would make it trickier to extend the program to handle different types of students. I am considering, as a compromise, to make a helper class that handles the prompting and collection of user input for each type of Student, which could then be called on by the main program. The advantage of this would be that the student classes don't have as much in them (so they're cleaner), but also they can be bundled with the helper classes if the input functionality is required. This also means more classes of Student could be added without having to make major changes to the main program, as long as helper classes are provided for these new classes. Also the helper class could be swapped for an alternative language version without having to make any changes to the class itself. What are the major advantages and disadvantages of the three different options for user input (fully encapsulated, helper class or in the main program)?

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  • Overriding the admin Media class

    - by shacker
    Given an admin media class that sets up a rich text editor, like: class TutorialAdmin(admin.ModelAdmin): fields... class Media: js = ['/paths/to/tinymce.js',] I would like the ability to selectively override js depending on a field value in the model it references. I've added a "use_editor" boolean to the Tutorial model. The question is, how can I detect whether the current instance has that bool set? I'd like to end up with something like: class Media: if self.use_editor: js = ['/path/to/tinymce.js',] else: js = '' Ideas? Thanks.

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  • 2 Classes need each other declared C++

    - by Prodigga
    I have a "Game" class which holds all the games settings and manages the game. I have a "Grid" class which is the grid the game is played on. The "Game" class initializes a "Grid" object as one of its members (passing itself ("this") as one of the parameters for "Grid"s constructor).. The "Grid" object therefor needs to deal with a "Game*" pointer. To do this it needs to know what "Game" is; i need to declare it before "Grid". But "Game" uses "Grid"...so it also needs "Grid" declared before it. so confused on how to include headers/etc correctly here..

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  • creative way for implementing Data object with its corresponding business logic class in java

    - by ekeren
    I have a class that need to be serialized (for both persistentcy and client-server communication) for simplicity's sake let's call the classes Business a BusinessData and I prefix for their Interfaces. All the getter and setter are delegated from Business class to BusinessData class. I thought about implementing IBusinessData interface that will contain all the getter and setters and IBusiness interface that will extend it. I can either make Business extend BuisnessData so I will not need to implement all getter and setter delegates, or make some abstract class ForwardingBusinessData that will only delegate getter and setters. Any of the above option I lose my hierarchy freedom, do any of you have any creative solutions for this problem... I also reviewed DAO pattern: http://java.sun.com/blueprints/patterns/DAO.html

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  • StructureMap - Injecting a dependency into a base class?

    - by David
    In my domain I have a handful of "processor" classes which hold the bulk of the business logic. Using StructureMap with default conventions, I inject repositories into those classes for their various IO (databases, file system, etc.). For example: public interface IHelloWorldProcessor { string HelloWorld(); } public class HelloWorldProcessor : IHelloWorldProcessor { private IDBRepository _dbRepository; public HelloWorldProcessor(IDBRepository dbRepository) { _dbRepository = dbrepository; } public string HelloWorld(){ return _dbRepository.GetHelloWorld(); } } Now, there are some repositories that I'd like to be available to all processors, so I made a base class like this: public class BaseProcessor { protected ICommonRepository _commonRepository; public BaseProcessor(ICommonRepository commonRepository) { _commonRepository = commonRepository; } } But when my other processors inherit from it, I get a compiler error on each one saying that there's no constructor for BaseProcessor which takes zero arguments. Is there a way to do what I'm trying to do here? That is, to have common dependencies injected into a base class that my other classes can use without having to write the injections into each one?

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  • Base class with abstract subclasses in C# ?

    - by Nick Brooks
    public abstract class Request { public class Parameters { //Threre are no members here //But there should be in inherited classes } public Request() { parameters = new Parameters(); } public Parameters parameters; } Two questions: How do I make it so I can add stuff to the constructor but the original constructor will still be executed? How do I make it so the subclasses can add members to the Parameters class?

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  • selenium cannot find element with class in IE

    - by Rob
    I'm using selenium_client with cucumber, webrat + IE As you'd expect, Firefox works fine. I've tried the following: selenium.is_visible("css=#flash .flash_notice") selenium.is_visible("xpath=//*[@id='flash']/*[@class='flash_notice]") selenium.is_visible("xpath=//*[@id='flash']/*[contains(@class,'flash_notice]')") both cannot find the element. I think it must be something to do with IE, looking closer at the html selenium returns from IE... It looks like this: <UL id=flash> <LI className=flash_notice>Deleted</LI> </UL> Notice IE returns the class attribute as className, is this confusing selenium? How can I get round this so that I can use the same statement for selenium using IE and Firefox Just to confuse us even more, this example works, confirming its something to do with checking the class attribute selenium.is_visible("xpath=//*[@id='flash']/*[. =\'Deleted\']")

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  • Defining a recursive function in a Prototype class?

    - by btl
    I'm trying to create an image rotator class that cycles through an arbitrary number of images in an unordered list. Is it possible to define a recursive function within a class declaration? E.g: var Rotator = Class.create() { initialize: function() { do something... this.rotate(); } rotate: function() { do something... this.rotate() } }

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  • Adding business logic to a domain class using a getter style method name

    - by Richard Paul
    I'm attempting to add a method to a grails domain class, e.g. class Item { String name String getReversedName() { name.reverse() } } When I attempt to load the application using grails console I get the following error: Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory':Invocation of init method failed; nested exception is org.hibernate.PropertyNotFoundException: Could not find a setter for property reversedName in class Item ... 18 more It looks like Hibernate is interpreting getReversedName() as a getter for a property, however in this case it is a derived field and hence should not be persisted. Obviously in my actual code the business logic I'm exposing is more complex but it isn't relevant to this question. I want to be able to call item.reversedName in my code/gsps. How can I provide property (getter) access to a method in a Grails domain class without Grails attempting to map it with Hibernate?

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  • Question regarding common class

    - by Rocky Singh
    I have following two classes: public class A : System.Web.UI.WebControls.Button { public virtual string X { get { object obj = ViewState["X"]; if (obj != null) return (string)obj; return null; } set { ViewState["X"] = value; } } protected override void OnLoad(EventArgs e) { X=2; } } and public class B : System.Web.UI.WebControls.TextBox { public virtual string X { get { object obj = ViewState["X"]; if (obj != null) return (string)obj; return null; } set { ViewState["X"] = value; } } protected override void OnLoad(EventArgs e) { X=2; } } As you must be seeing the class A and B have exactly the same code , my question is how can I make a common class for it and use these two classes.

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  • Inheritance and choose constructor from base class

    - by myle
    My question is rather simple, but I am stuck. How can I choose the desired constructor from base class? // node.h #ifndef NODE_H #define NODE_H #include <vector> // definition of an exception-class class WrongBoundsException { }; class Node { public: ... Node(double, double, std::vector<double>&) throw (WrongBoundsException); ... }; #endif // InternalNode.h #ifndef INTERNALNODE_H #define INTERNALNODE_H #include <vector> #include "Node.h" class InternalNode : public Node { public: // the position of the leftmost child (child left) int left_child; // the position of the parent int parent; InternalNode(double, double, std::vector<double>&, int parent, int left_child) throw (WrongBoundsException); private: int abcd; }; #endif // InternalNode.cpp #include "InternalNode.h" #define UNDEFINED_CHILD -1 #define ROOT -1 // Here is the problem InternalNode::InternalNode(double a, double b, std::vector<double> &v, int par, int lc) throw (WrongBoundsException) : Node(a, b, v), parent(par), left_child(lc) { std::cout << par << std::endl; } I get: $ g++ InternalNode.cpp InternalNode.cpp:16: error: declaration of ‘InternalNode::InternalNode(double, double, std::vector &, int, int) throw (WrongBoundsException)’ throws different exceptions InternalNode.h:17: error: from previous declaration ‘InternalNode::InternalNode(double, double, std::vector &, int, int)’ UPDATE 0: Fixed missing : UPDATE 1: Fixed throw exception

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