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  • Accessing constructor from abstract base class with reflection

    - by craesh
    Hi! I'm playing around with Java's Reflection. I have an abstract class Base with a constructor. abstract class Base { public Base( String foo ) { // do some magic } } I have some further classes extending Base. They don't contain much logic. I want to instantiate them with Base's constructor, without having to write some proxy contructors in those derived classes. And of course, I want to instantiate those derived classes with Reflection. Say: Class cls = SomeDerivedClass.class; Constructor constr; constr = cls.getConstructor( new Class[] { String.class } ); // will return null Class clsBase = Base.class; constr = clsBase.getConstructor( new Class[] { String.class } ); // ok Base obj = (Base) constr.newInstance( new Object[] { "foo" } ); // will throw InstantiationException because it belongs to an abstract class Any ideas, how I can instantiate a derived class with Base's constructor? Or must I declare those dumb proxy constructors?

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  • How do I run jQuery form validation by class?

    - by joshcomley
    Hi there, I've been using the jQuery form validator, but I can't seem to figure out how to trigger it by class. Take this example: $("#myform").validate({ rules: { field: { required: true, date: true } } }); Where field it is expecting the name of the particular input. But, what if I have the following: <input class="date".... /> How can I tell the validator to validate all inputs with a "date" class as a date?

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  • What am I not getting about this abstract class implementation?

    - by Schnapple
    PREFACE: I'm relatively inexperienced in C++ so this very well could be a Day 1 n00b question. I'm working on something whose long term goal is to be portable across multiple operating systems. I have the following files: Utilities.h #include <string> class Utilities { public: Utilities() { }; virtual ~Utilities() { }; virtual std::string ParseString(std::string const& RawString) = 0; }; UtilitiesWin.h (for the Windows class/implementation) #include <string> #include "Utilities.h" class UtilitiesWin : public Utilities { public: UtilitiesWin() { }; virtual ~UtilitiesWin() { }; virtual std::string ParseString(std::string const& RawString); }; UtilitiesWin.cpp #include <string> #include "UtilitiesWin.h" std::string UtilitiesWin::ParseString(std::string const& RawString) { // Magic happens here! // I'll put in a line of code to make it seem valid return ""; } So then elsewhere in my code I have this #include <string> #include "Utilities.h" void SomeProgram::SomeMethod() { Utilities *u = new Utilities(); StringData = u->ParseString(StringData); // StringData defined elsewhere } The compiler (Visual Studio 2008) is dying on the instance declaration c:\somepath\somecode.cpp(3) : error C2259: 'Utilities' : cannot instantiate abstract class due to following members: 'std::string Utilities::ParseString(const std::string &)' : is abstract c:\somepath\utilities.h(9) : see declaration of 'Utilities::ParseString' So in this case what I'm wanting to do is use the abstract class (Utilities) like an interface and have it know to go to the implemented version (UtilitiesWin). Obviously I'm doing something wrong but I'm not sure what. It occurs to me as I'm writing this that there's probably a crucial connection between the UtilitiesWin implementation of the Utilities abstract class that I've missed, but I'm not sure where. I mean, the following works #include <string> #include "UtilitiesWin.h" void SomeProgram::SomeMethod() { Utilities *u = new UtilitiesWin(); StringData = u->ParseString(StringData); // StringData defined elsewhere } but it means I'd have to conditionally go through the different versions later (i.e., UtilitiesMac(), UtilitiesLinux(), etc.) What have I missed here?

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  • Python Introspection: How to get varnames of class methods?

    - by daccle
    I want to get the names of the keyword arguments of the methods of a class. I think I understood how to get the names of the methods and how to get the variable names of a specific method, but I don't get how to combine these: class A(object): def A1(self, test1=None): self.test1 = test1 def A2(self, test2=None): self.test2 = test2 def A3(self): pass def A4(self, test4=None, test5=None): self.test4 = test4 self.test5 = test5 a = A() # to get the names of the methods: for methodname in a.__class__.__dict__.keys(): print methodname # to get the variable names of a specific method: for varname in a.A1.__func__.__code__.co_varnames: print varname # I want to have something like this: for function in class: print function.name for varname in function: print varname # desired output: A1 self test1 A2 self test2 A3 self A4 self test4 test5

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  • Is it good to subclass a class only to separate some functional parts?

    - by prostynick
    Suppose we have abstract class A (all examples in C#) public abstract class A { private Foo foo; public A() { } public void DoSomethingUsingFoo() { //stuff } public void DoSomethingElseUsingFoo() { //stuff } //a lot of other stuff... } But we are able to split it into two classes A and B: public abstract class A { public A() { } //a lot of stuff... } public abstract class B : A { private Foo foo; public B() : base() { } public void DoSomethingUsingFoo() { //stuff } public void DoSomethingElseUsingFoo() { //stuff } //nothing else or just some overrides of A stuff } That's good, but we are 99.99% sure, that no one will ever subclass A, because functionality in B is very important. Is it still good to have two separate classes only to split some code into two parts and to separate functional elements?

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  • which should be drawn first , class or sequence diagram?

    - by m0j1
    hi , I've had this discussion with my professor at college about UML diagrams . hi believes that sequence diagrams should be drawn before getting to class diagrams . but I think the opposite . I think after finishing the usecase diagram , the next diagram should be class diagram and after that we should get to sequence diagram . Rational rose requires us to use the classes in sequence diagram, which are already in class diagram . can anyone help me with this? thanks

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  • Differences between a conceptual UML class diagram and an ERD?

    - by Adam
    If I create a conceptual class diagram such that each class captures 'name' and 'attributes' but not 'operations', have I not basically created what would be otherwise considered an ERD? I'm trying to gain an understanding of what the differences are between creating a conceptual class diagram as I have described versus calling it a ERD? If these are still two different animals, can somebody please explain what the differences are?

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  • Meaning of the "Unloading class" messages

    - by elec
    Anyone can explain why the lines below appear in the output console at runtime ? (one possible answer would be full permGen, but this can be ruled out since the program only uses 24MB out of the max100MB available in PermGen) [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor28] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor14] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor4] [Unloading class sun.reflect.GeneratedMethodAccessor5] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor38] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor36] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor22] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor8] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor39] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor16] [Unloading class sun.reflect.GeneratedSerializationConstructorAccessor2] [Unloading class sun.reflect.GeneratedConstructorAccessor1] The program runs with the following params: -Xmx160M -XX:MaxPermSize=96M -XX:PermSize=96M -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:+PrintGCTaskTimeStamps -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintGCTimeStamps -verbose:gc -Xloggc:/logs/gc.log There's plenty of space in the heap and in permGen.

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  • Do I still have to implement a singleton class by hand in .net, even when using .Net4.0?

    - by Hamish Grubijan
    Once the singleton pattern is understood, writing subsequent singleton classes in C# is a brainless exercise. I would hope that the framework would help you by providing an interface or a base class to do that. Here is how I envision it: public sealed class Schablone : ISingleton<Schablone> { // Stuff forced by the interface goes here // Extra logic goes here } Does what I am looking for exist? Is there some syntactic sugar for constructing a singleton class - whether with an interface, a class attribute, etc.? Can one write a useful and bullet-proof ISingleton themselves? Care to try? Thanks!

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  • Can pydoc/help hide the documentation for inherited class methods and attributes?

    - by EOL
    When declaring a class that inherits from a specific class: class C(dict): added_attribute = 0 the documentation for C lists all the methods of dict (either through help(C) or pydoc). Is there a way to hide the inherited methods from the automatically generated documentation (the documentation string can refer to the base class, for non-overwritten methods)? This would be useful: pydoc lists the functions defined in a module after its classes. Thus, when the classes have a very long documentation, a lot of less than useful information is printed before the new functions provided by the module are presented, which makes the documentation harder to exploit (you have to skip all the documentation for the inherited methods until you reach something specific to the module being documented).

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  • How to make a Scala Applet whose Applet class is a singleton?

    - by Jamie
    Hi, I don't know if a solution exists but it would be highly desirable. I'm making a Scala Applet, and I want the main Applet class to be a singleton so it can be accessed elsewhere in the applet, sort of like: object App extends Applet { def init { // do init here } } Instead I have to make the App class a normal instantiatable class otherwise it complains because the contructor is private. So the ugly hack I have is to go: object A { var pp: App = null } class App extends Applet { A.pp = this def init { // do init here } } I really hate this, and is one of the reasons I don't like making applets in Scala right now. Any better solution? It would be nice...

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  • How do you learn a class hierarchy quickly?

    - by rsteckly
    Hi, Something I don't enjoy about programming is learning a new API. For example, right now I'm trying to learn Windows Identity Foundation. Its frustrating because I'm going to spend the bulk of the time learning how a few classes work and actually only write several lines of code. In .NET, there are so many types that I seem to spend more time hunting around in msdn for a class than writing code. It also interrupts my workflow while I'm working because I have to type a little bit than look something up. Obviously, I don't have to do this for the basic classes. Whenever new things come though there is definitely some looking up to do. Then I often don't reuse that class enough to really review it or bring it into action. I'm wondering if anybody out there has a found a way to memorize (or look up more efficiently) these object model hierarchies?

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  • Instance_eval: why the class of subclass is superclass

    - by Raj
    def singleton_class class << self self end end class Human proc = lambda { puts 'proc says my class is ' + self.name.to_s } singleton_class.instance_eval do define_method(:lab) do proc.call end end end class Developer < Human end Human.lab # class is Human Developer.lab # class is Human ; oops Following solution works. def singleton_class class << self self end end class Human proc = lambda { puts 'proc says my class is ' + self.name.to_s } singleton_class.instance_eval do define_method(:lab) do self.instance_eval &proc end end end class Developer < Human end Human.lab # class is Human Developer.lab # class is Human ; oops Why Developer.lab is reporting that it is Human ? And what can be done so that proc reports Developer when Developer.lab is invoked.

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  • In Ruby or Python can the very idea of Class be rewritten?

    - by John Berryman
    Howdy All... first time at stack overflow. I'm looking into using some of the metaprogramming features provided by Ruby or Python, but first I need to know the extent to which they will allow me to extend the language. The main thing I need to be able to do is to rewrite the concept of Class. This doesn't mean that I want to rewrite a specific class during run time, but rather I want to make my own conceptualization of what a Class is. To be a smidge more specific here, I want to make something that is like what people normally call a Class, but I want to follow an "open world" assumption. In the "closed world" of normal Classes, if I declare Poodle to be a subclass of Dog to be a subclass of Animal, then I know that Poodle is not going to also be a type of FurCoat. However, in an open world Class, then the Poodle object I've defined may or may not be and object of type FurCoat and we won't know for sure until I explain that I can wear the poodle. (Poor poodle.) This all has to do with a study I'm doing concerning OWL ontologies. Just so you know, I've tried to find information online, but due to the overloading of terms here I haven't found anything helpful. Super thanks, John

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  • PHP: Class extends problem "Call to private method ... from context ..."

    - by sombe
    I have 3 classes in WordPress (the question itself is unrelated to it): class WP_Widget class Theme_Widget extends WP_Widget class Specific_Widget extends Theme_Widget Essentially Theme_Widget contains some extension functions to the basic WP_Widget. Inside Specific_Widget I call one of Theme_Widget's methods: class Specific_Widget { function __construct() { $this->some_method_that_belongs_to_Theme_Widget(); } } When I instantiate Specific_Widget, PHP throws a fatal error as follows: Fatal error: Call to private method Theme_Widget::some_method_that_belongs_to_Theme_Widget() from context 'Specific_Widget' in ... Do you have an idea as to how I can resolve this? This is the first time I've received this error from PHP. Could it be derive from WordPress itself?

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  • Why can't I create an abstract constructor on an abstract C# class?

    - by Anthony D
    I am creating an abstract class. I want each of my derived classes to be forced to implement a specific signature of constructor. As such, I did what I would have done has I wanted to force them to implement a method, I made an abstract one. public abstract class A { abstract A(int a, int b); } However I get a message saying the abstract modifier is invalid on this item. My goal was to force some code like this. public class B : A { public B(int a, int b) : base(a, b) { //Some other awesome code. } } This is all C# .NET code. Can anyone help me out? Update 1 I wanted to add some things. What I ended up with was this. private A() { } protected A(int a, int b) { //Code } That does what some folks are saying, default is private, and the class needs to implement a constructor. However that doesn't FORCE a constructor with the signature A(int a, int b). public abstract class A { protected abstract A(int a, int b) { } } Update 2 I should be clear, to work around this I made my default constructor private, and my other constructor protected. I am not really looking for a way to make my code work. I took care of that. I am looking to understand why C# does not let you do this.

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  • Are reference attributes destroyed when class is destroyed in C++?

    - by Genba
    Suppose I have a C++ class with an attribute that is a reference: class ClassB { ClassA &ref; public: ClassB(ClassA &_ref); } Of course, the constructor is defined this way: ClassB::ClassB(ClassA &_ref) : ref(_ref) { /* ... */ } My question is: When an instance of class 'ClassB' is destroyed, is the object referenced by 'ClassB::ref' also destroyed?

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  • Can I use an abstract class instead of a private __construct() when creating a singleton in PHP?

    - by Pheter
    When creating a Singleton in PHP, I ensure that it cannot be instantiated by doing the following: class Singleton { private function __construct() {} private function __clone() {} public static function getInstance() {} } However, I realised that defining a class as 'abstract' means that it cannot be instantiated. So is there anything wrong with doing the following instead: abstract class Singleton { public static function getInstance() {} } The second scenario allows me to write fewer lines of code which would be nice. (Not that it actually makes much of a difference.)

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  • How can I fix Grails error: "No domain class found for name PrivacyOptions. Please try again and e

    - by ?????
    I'm just getting started with Groovy/Grails. I added a new domain controller to my project, and generate-controller doesn't like it. There are other indications something's wrong: If I run the app no table is actually created in the database for this. I've reduced the DomainController to one String field and no constraints, just to make sure there wasn't something wrong with my specification. I also tried renaming it, just in case there was something about the original name (Privacy) that conflicted with something. I'm sure I have the correct name, and that the file is called PrivacyOptions.groovy and inside the class is also called PrivacyOptions. Here's the error: Running script /opt/local/grails/scripts/GenerateController.groovy Environment set to development Domain class not found in grails-app/domain, trying hibernate mapped classes... No domain class found for name PrivacyOptions. Please try again and enter a valid domain class name

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  • Adding a first and last class to Wordpress' widget contents

    - by user571188
    In Wordpress, I'm looking for some way to add a "last" and a "first" class to list items inside Wordpress widgets. The HTML could look like this: <div class="widget-area"> <ul > <li class="widget_recent_comments"> <h3 class="widget-title">Recent comments</h3> <ul id="recentcomments"> <li class="recentcomments">Comment 1</li> <li class="recentcomments">Comment 2</li> <li class="recentcomments">Comment 3</li> <li class="recentcomments">Comment 4</li> </ul> </li> <li class="widget_my_links"> <h3 class="widget-title">My links</h3> <ul id="my-links"> <li class="item">Link 1</li> <li class="item">Link 2</li> <li class="item">Link 3</li> <li class="item">Link 4</li> <li class="item">Link 5</li> </ul> </li> </ul></div> In this example above i'd like to have first/last classes added to the li with "Comment 1", "Comment 4", "Link 1" and "Link 5". Is there an easy workaround for this? (I don't want to do this with javascript) Thank you.

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  • How can I create an instance of a class that I can use is more than one place in c#

    - by user1743574
    So I've been working on a class that details students of a university. I have one button that sets the details to a new instance of a class, and another to check if the student passed, through a method in my Class. The problem is that I create an instance of a class in the first button to add the values from what the user input, but I cannot use the second button to access the instance of the class created in the first button. private void button3_Click(object sender, EventArgs e) { Student student1 = new Student(); label1.Text = student1.text(); if (student1.hasPassed() == true) { passfailtextbox.Text = "Pass"; } else { passfailtextbox.Text = "Fail"; } } private void button1_Click(object sender, EventArgs e) { Student student1 = new Student(); student1.FirstName = firstnamebox.Text; student1.SecondName = secondnamebox.Text; student1.DateofBirth = DateTime.Parse(dobtextbox.Text).Date; student1.Course = coursetextbox.Text; student1.MatriculationNumber = int.Parse(matriculationtextbox.Text); student1.YearMark = double.Parse(yearmarktextbox.Text); } public Boolean hasPassed() { if (YearMark < 40) { return false; } else { return true; } } public string text() { return "Student" + " " + firstname + " " + secondname + " " + course + " " + dob.ToString() + " " + matriculationnumber.ToString() + " " + yearmark.ToString() ; }

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  • Mercurial: Class library that will exist for both .NET 3.5 and 4.0?

    - by Lasse V. Karlsen
    I have a rather big class library written in .NET 3.5 that I'd like to upgrade to make available for .NET 4.0 as well. In that process, I will rip out a lot of old junk, and rewrite some code to better take advantage of the new classes and support in .NET 4.0 (like TPL.) The class libraries will thus diverge, but still be similar enough that some bug-fixes can be done to both in the same manner. How should I best organize this class library in Mercurial? I'm using Kiln (fogbugz) if that matters. I'm thinking: Named branches in one repository, can then transplant any bugfixes from one to the other Unnamed branches in one repository, can also transplant, but I think this will look messy Separate repositories, will have to reimplement the bugfixes (or use a non-mercurial-integraded compare tool to help me) What would you do? (any other alternatives that I haven't though of is welcome as well.) Note that the class libraries will diverge pretty heavily in areas, I have some remnants of old collection-type code that does something similar to Linq that I will remove, and some code that uses it that I will rewrite to use the Linq-methods instead. As such, just copying the project files and using #if NET40..#endif sections is not going to work out. Also, the 3.5 version of the class library will not be getting many new features, mostly just critical bug-fixes, so keeping both versions equally "alive" isn't really necessary. Thus, separate copies of all the files are good enough.

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  • How to align C++ class member names in one column in emacs ?

    - by KotBerbelot
    I would like to align all C++ class member names ( do not confuse with member types ) in one column. Lets look at the example of what we have at entrance: class Foo { public: void method1( ); int method2( ); const Bar * method3( ) const; protected: float m_member; }; and this is what we would like to have at the end: class Foo { public: void method1( ); int method2( ); const Bar * method3( ) const; protected: float m_member; }; So the longest member type declaration defines the column to which class member names will be aligned. How can i perform such transformation in emacs ?

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