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  • C++ initializing constants and inheritance

    - by pingvinus
    I want to initialize constant in child-class, instead of base class. And use it to get rid of dynamic memory allocation (I know array sizes already, and there will be a few child-classes with different constants). So I try: class A { public: const int x; A() : x(0) {} A(int x) : x(x) {} void f() { double y[this->x]; } }; class B : A { B() : A(2) {} }; Pretty simple, but compiler says: error C2057: expected constant expression How can I say to compiler, that it is really a constant?

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  • Adding a Categorylist to all pages with MVC4

    - by Sidriel
    I'm new with MVC4 and just MVC. I have a homecontroller and a categorycontroller. The categorycontroller sends data from the model to the categoryIndex view. That's works fine. But now I want to add the categorylist on all the available controllers. I already fixed this to add in all classes return view(db.categorys.ToList()); and add categoryIndex to the shared folder. In _layout.cshtml I'm adding a@RenderPage("~/")` and this works. But when I have to pass more than only the (db.categorys.ToList()) in the return it goes wrong. How can I fixed this problem. How do I add the categorylist too every controller and page properly?

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  • mysql eliminate responses under certain condition with join

    - by Dustin
    Forgive me if this is an easy question. I teach classes and want to be able to select those students who have taken one class, but not another class. I have two tables: lessons_slots which is the table for every class such as: -------------------- -ID name slots- -1 basics 10 - -2 advanced 10 - -3 basics 10 - --------------------- The other table is class_roll, which holds enrollment info, such as: -------------------- -sID classid firstname lastname- -1 1 Jo Schmo -2 1 Person Two ... -13 2 Jo Schmo --------------------- What I want to do, I select everyone who has not had the advanced class (for example). I've tried doing SELECT * FROM lessons_slots LEFT JOIN class_roll ON lessons_slots.ID = class_roll.classid WHERE lessons_slots.name != 'advanced' But that doesn't work. Any ideas?

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  • TCP/IP and UDP Questions and very small application for interview

    - by Shantanu Gupta
    I am going for an interview day after tomorrow where i will be asked vaious questions related to TCP/IP and UDP. As of now i have prepared theoritical knowledge about it. But now I am looking up for gaining some practicle knowledge related to how it works in a network. What all is going in vaious .NET classes. I want to create a very small application like a chat or something that can make me all these concepts very much clear. Could you please suggest some questions related to TCP/IP that you generally ask or that you might have faced. How communication is going from server to client. Right now I am studying TcpClient, TcpListener and UdpClient Class but I want to implement all of them so as to get aware about its working. Is Chat application a Tcp/IP application ? I would appreciate your help.

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  • Using multiple databases within one application

    - by Alex
    I have a web application made for several groups of people not connected with each other. Instead of using one database for all of them, I'm thinking about making separate databases. This will improve the speed of the queries and make me free from checking to what group the user belongs. But since I'm working with LINQ to SQL, my classes are explicitly connected with the databases, so I will have to make separate DataContexts for all of the databases. So how can I solve this problem? Or should I just not bother and use one database only?

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  • How to copy value from class X to class Y with the same property name in c#?

    - by Samnang
    Suppose I have two classes: public class Student { public int Id {get; set;} public string Name {get; set;} public IList<Course> Courses{ get; set;} } public class StudentDTO { public int Id {get; set;} public string Name {get; set;} public IList<CourseDTO> Courses{ get; set;} } I would like to copy value from Student class to StudentDTO class: var student = new Student(); StudentDTO studentDTO = student; How can I do that by reflection or other solution?

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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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  • Using a backwards relation (i.e FOO_set) for ModelChoiceField in Django

    - by Bwmat
    I have a model called Movie, which has a ManyToManyField called director to a model called Person, and I'm trying to create a form with ModelChoiceField like so: class MovieSearchForm(forms.Form): producer = forms.ModelChoiceField(label='Produced by', queryset=movies.models.Person.producer_set, required=False) but this seems to be failing to compile (I'm getting a ViewDoesNotExist exception for the view that uses the form, but it goes away if I just replace the queryset with all the person objects), I'm guessing because '.producer_set' is being evaluated too 'early'. How can I get this work? here are the relevant parts of the movie/person classes: class Person(models.Model): name = models.CharField(max_length=100) class Movie(models.Model): ... producer = models.ForeignKey(Person, related_name="producers") director = models.ForeignKey(Person, related_name="directors") What I'm trying to do is get ever Person who is used in the producer field of some Movie.

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  • Python unittest with expensive setup

    - by Staale
    My test file is basically: class Test(unittest.TestCase): def testOk(): pass if __name__ == "__main__": expensiveSetup() try: unittest.main() finally: cleanUp() However, I do wish to run my test through Netbeans testing tools, and to do that I need unittests that don't rely on an environment setup done in main. Looking at http://stackoverflow.com/questions/402483/caching-result-of-setup-using-python-unittest - it recommends using Nose. However, I don't think Netbeans supports this. I didn't find any information indicating that it does. Additionally, I am the only one here actually writing tests, so I don't want to introduce additional dependencies for the other 2 developers unless they are needed. How can I do the setup and cleanup once for all the tests in my TestSuite? The expensive setup here is creating some files with dummy data, as well as setting up and tearing down a simple xml-rpc server. I also have 2 test classes, one testing locally and one testing all methods over xml-rpc.

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  • Images or files in GNU Smalltalk?

    - by Marc
    Hi, I'm new to Smalltalk. I think I understand the basics of the language and now want to start with GNU Smalltalk (as it's free and has bindings for GTK). As I'm coming from the PHP and Java-Corner, I'm not familiar with the concept of the Smalltalk images. And I even read now, that you don't need to use images in GNU Smalltalk. Now I'm confused ;-) So is it possible to work with files and to include the classes I need with the PackageLoader class? I would be happy when I could use my favourite texteditor (vim) for coding instead of an IDE, too ;-) Please enlight me :-)

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  • how to import Java class with Python using Eclipse?

    - by JChao
    Hi, I'm trying to write Jython where the Python file imports classes from Java I'm using Eclipse with PyDev. My Python code looks like: from eclipsejavatest import eclipseJavaTest from eclipsejavatest import JavaClass class eclipsePyPrint(eclipseJavaTest): def eclipsepyMain(self): print "python main method" eclipseJavaTest.printerCount(4) print eclipseJavaTest.gotoPython() eclipseJavaTest.printerSentence() samplepyClass = JavaClass("Jython plain") samplepyClass.setName("jython fancy") print samplepyClass.getName() but I'm getting the error ImportError: No module named eclipsejavatest The Python project references the Java project. I've tried exporting the Java project and adding the .jar to the Jython Class Path for the Python project. I'm not sure what to do to get this to work.

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  • Advanced queries in HBase

    - by Teflon Ted
    Given the following HBase schema scenario (from the official FAQ)... How would you design an Hbase table for many-to-many association between two entities, for example Student and Course? I would define two tables: Student: student id student data (name, address, ...) courses (use course ids as column qualifiers here) Course: course id course data (name, syllabus, ...) students (use student ids as column qualifiers here) This schema gives you fast access to the queries, show all classes for a student (student table, courses family), or all students for a class (courses table, students family). How would you satisfy the request: "Give me all the students that share at least two courses in common"? Can you build a "query" in HBase that will return that set, or do you have to retrieve all the pertinent data and crunch it yourself in code?

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  • Best practice in Rails when editing scaffold made pages

    - by abegbg
    I have a best practice question. I have two classes, company and category. They have a many-to-many relationship. When clicking a category I shall go to a page showing all companies with the chosen category. Pretty straight forward. My question is: Should I list all the companies on the companies/index.html.erb after filtering the companies in the controller? or Should I list all the companies on the categories/show.html.erb page? or Should I do a completely new page, since it doesn't really fit into any of the two above? Do you generally make a new page when your goal doesn't fit the scaffold made pages or do you use them quite freely? I am working/learning alone with rails, so there are a lot of best practice questions popping up all the time. Cheers Carl

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  • NSUserDefaults: detecting nil

    - by alJaree
    I have some code in my classes to read from NSUserDefaults NSUserDefaults *defs = [NSUserDefaults standardUserDefaults]; score = [defs integerForKey:@"score"]; this causes a crash. Im guessing it is because the score value is nil or doesnt exist. How can I check if it is nil? EDIT. The following code causes a crash when storing to NSUserDefaults. NSUserDefaults *defs = [NSUserDefaults standardUserDefaults]; [defs setInteger:0 forKey:@"score"]; [defs setInteger:3 forKey:@"lives"]; [defs release]; Im not sure what the issue is On some crashes there isnt even a crash report in the console. Thanks

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  • C++ vtable resolving with virtual inheritance

    - by Tomas Cokis
    I was curious about C++ and virtual inheritance - in particular, the way that vtable conflicts are resolved between bass and child classes. I won't pretend to understand the specifics on how they work, but what I've gleamed so far is that their is a small delay caused by using virtual functions due to that resolution. My question then is if the base class is blank - ie, its virtual functions are defined as: virtual void doStuff() = 0; Does this mean that the resolution is not necessary, because there's only one set of functions to pick from? Forgive me if this is an stupid question - as I said, I don't understand how vtables work so I don't really know any better.

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  • Inheritance and Implicit Type Casting

    - by Josué Molina
    Suppose I have the following three classes: class Animal {}; class Human : public Animal {}; class Dog : public Animal { public: void setOwner(Animal* owner) { this->owner = owner; } private: Animal* owner; }; Why is the following allowed, and what exactly is happening? Dog d; Human h; d.setOwner(&h); // ? At first, I tried to cast it like this d.setOwner(&(Animal)h), but the compiler gave me a warning, and I hit a run-time error. Edit: the warning the compiler gave me was "taking address of temporary". Why is this so?

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  • How to sort a list by the 2nd tuple element in python and C#

    - by user350468
    I had a list of tuples where every tuple consists of two integers and I wanted to sort by the 2nd integer. After looking in the python help I got this: sorted(myList, key=lambda x: x[1]) which is great. My question is, is there an equally succinct way of doing this in C# (the language I have to work in)? I know the obvious answer involving creating classes and specifying an anonymous delegate for the whole compare step but perhaps there is a linq oriented way as well. Thanks in advance for any suggestions.

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  • Architecting a generic search result web control

    - by Bartek Tatkowski
    In a project I'm currently working for we've stumbled upon the need for several kinds of search results presentation controls. The search result are similar, but not identical. For example, in the "office search" result we might want to present the office name and location, while in the "document search" could contain document name, author and publishing date. These fields should be sortable. My current strategy is to employ the Factory pattern and do something like this: ISearchResult officeResults = SearchResultFactory.CreateOfficeSearchResults(data); ISearchResult documentResults = SearchResultFactory.CreateDocumentSearchResults(data); The problem is: I don't know how to implement the markup code. Should I just do Controls.Add(officeResults); in the containing page? Or is there some ASPX trickery to create generic web controls? Or maybe I'm overthinking this and just should create five classes? ;)

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  • packing fields of a class into a byte array in c#

    - by alex
    Hi all: I am trying to create a fast way to convert c# classes into byte array. I thought of serializing the class directly to a byte array using an example I found: // Convert an object to a byte array private byte[] ObjectToByteArray(Object obj) { if(obj == null) return null; BinaryFormatter bf = new BinaryFormatter(); MemoryStream ms = new MemoryStream(); bf.Serialize(ms, obj); return ms.ToArray(); } But the byte array I got contains some other information that are not related to the fields in the class. I guess it is also converting the Properties of the class. Is there a way to serialize only the fields of the class to a byte array? Thanks

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  • Session State Anti-Pattern

    - by Curiosity
    I know the SOLID principles and other design patterns fairly well and have been programming for some time now - seeing many a bit of code throughout the years. Having said that, I'm having trouble coming up with a name to give the pattern, or lack thereof, to bits of code I've been dealing with at a current engagement. The application is an ASP.NET C# WebForms application, backed by a SQL Server/Mainframe backend (more mainframe than backend) and it's riddled with Session State properties being accessed/mutated from multiple pages/classes. Accessing/mutating global variables/application state was usually shunned upon while I was in school. Apparently the creators of this magnificent application didn't think it was such a bad idea. Question: Is there a name for such a pattern/anti-pattern that relies so heavily on Session State? I'd like to call the pig by its name ...

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  • Inheritance vs specific types in Financial Modelling for cashflows

    - by BlueTrin
    Hello, I have to program some financial applications where I have to represent a schedule of flows. The flows can be of 3 types: - fee flow (just a lump payment at some date) - floating rate flow (the flow is dependant of an interest rate to be determined at a later date) - fixed rate flow (the flow is dependant of an interest rate determined when the deal is done) I need to keep the whole information and I need to represent a schedule of these flows. Originally I wanted to use inheritance and create three classes FeeFlow, FloatingFlow, FixedFlow all inheriting from ICashFlow and implement some method GetFlowType() returning an enum then I could dynamic_cast the object to the correct type. That would allow me to have only one vector to represent my schedule. What do you think of this design, should I rather use three vectors vector, vector and vector to avoid the dynamic casts ?

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  • What comes first in Ruby's object model?

    - by Timothy
    I've been reading Metaprogramming Ruby and the object model like the chicken or egg dilemma. In Ruby 1.8, the Object class is an instance of Class. Module's superclass is Object and is an instance of Class. Class' superclass is Module, and it is an instance of Class (self-referential). Say class SomeClass; end is defined somewhere; SomeClass is an instance of Class, however its superclass is Object. Why does an instance of Class have Object as the superclass instead of nil? Also, if Object is to exist, then Class has to exist, but then Module has to exist, but for Module to exist Object has to exist. How are these classes created?

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  • How to seralize only some properties in .Net?

    - by Beta033
    This is for a web project so i have several classes that inherit from Web.UI. I only want to serialize very particular properties (basically, only local properties) I'm aware of the XMLIgnore property that can be placed on a property to ignore items, but this won't work in my context since that would require modifying a bunch of stuff that i really don't want to modify (and probably can't). So how do i tell the xml serializer to ignore everything except for X and Y or tell it to seralize just X and Y? i could just create my own xml in a string builder or something and if that's the only way, so be it. however i'm looking for a method that will employ the built in XML stuff. Thanks

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  • defining information out of class

    - by calccrypto
    is there a way to define a value within a class in the __init__ part, send it to some variable outside of the class without calling another function within the class? like class c: def __init__(self, a): self.a = a b = 4 # do something like this so that outside of class c, # b is set to 4 automatically when i use class c def function(self): ... # whatever. this doesnt matter i have multiple classes that have different values for b. i could just make a list that tells the computer to change b, but i would rather set b within each class

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  • Navigation properties not set when using ADO.NET Mocking Context Generator

    - by olenak
    I am using ADO.NET Mocking Context Generator plugin for my Entity Framework model. I have not started on using mocks yet, just trying to fix generated entity and context classes to make application run as before without exceptions. I've already fixed T4 template to support SaveChanges method. Now I've got another problem: when I try to access any navigation property it is set to null. All the primitive fields inherited from DB table are set and correct. So what I am doing is the following using (var context = MyContext()) { var order = context.Orders.Where(p => p.Id == 7); var product = order.Products; } in this case product is set to null. But that was not a case while using default code generator, it used to return real product object. Thanks ahead for any suggestions!

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