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  • C++ privately contructed class

    - by Nona Urbiz
    How can I call a function and keep my constructor private? If I make the class static, I need to declare an object name which the compiler uses to call the constructor, which it cannot if the constructor is private (also the object would be extraneous). Here is the code I am attempting to use (it is not compilable): I want to keep the constructor private because I will later be doing a lot of checks before adding an object, modifying previous objects when all submitted variables are not unique rather than creating new objects. #include <iostream> #include <fstream> #include <regex> #include <string> #include <list> #include <map> using namespace std; using namespace tr1; class Referral { public: string url; map<string, int> keywords; static bool submit(string url, string keyword, int occurrences) { //if(Referrals.all.size == 0){ // Referral(url, keyword, occurrences); //} } private: list<string> urls; Referral(string url, string keyword, int occurrences) { url = url; keywords[keyword] = occurrences; Referrals.all.push_back(this); } }; struct All { list<Referral> all; }Referrals; int main() { Referral.submit("url", "keyword", 1); }

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  • How to get the parameter names of an object's constructors (reflection)?

    - by Tom
    Say I somehow got an object reference from an other class: Object myObj = anObject; Now I can get the class of this object: Class objClass = myObj.getClass(); Now, I can get all constructors of this class: Constructor[] constructors = objClass.getConstructors(); Now, I can loop every constructor: if (constructors.length > 0) { for (int i = 0; i < constructors.length; i++) { System.out.println(constructors[i]); } } This is already giving me a good summary of the constructor, for example a constructor public Test(String paramName) is shown as public Test(java.lang.String) Instead of giving me the class type however, I want to get the name of the parameter.. in this case "paramName". How would I do that? I tried the following without success: if (constructors.length > 0) { for (int iCon = 0; iCon < constructors.length; iCon++) { Class[] params = constructors[iCon].getParameterTypes(); if (params.length > 0) { for (int iPar = 0; iPar < params.length; iPar++) { Field fields[] = params[iPar].getDeclaredFields(); for (int iFields = 0; iFields < fields.length; iFields++) { String fieldName = fields[i].getName(); System.out.println(fieldName); } } } } } Unfortunately, this is not giving me the expected result. Could anyone tell me how I should do this or what I am doing wrong? Thanks!

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  • C++ Why is the converter constructor implicitly called?

    - by ShaChris23
    Why is the Child class's converter constructor called in the code below? I mean, it automatically converts Base to Child via the Child converter constructor. The code below compiles, but shouldn't it not compile since I haven't provided bool Child::operator!=(Base const&)? class Base { }; class Child : public Base { public: Child() {} Child(Base const& base_) : Base(base_) { std::cout <<"should never called!"; } bool operator!=(Child const&) { return true; } }; void main() { Base base; Child child; if(child != base) std::cout << "not equal"; else std::cout << "equal"; }

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  • Serialize WPF component using XamlWriter without default constructor

    - by mizipzor
    Ive found out that you can serialize a wpf component, in my example a FixedDocument, using the XamlWriter and a MemoryStream: FixedDocument doc = GetDocument(); MemoryStream stream = new MemoryStream(); XamlWriter.Save(doc, stream); And then to get it back: stream.Seek(0, SeekOrigin.Begin); FixedDocument result = (FixedDocument)XamlReader.Load(stream); return result; However, now I need to be able to serialize a DocumentPage as well. Which lacks a default constructor which makes the XamlReader.Load call throw an exception. Is there a way to serialize a wpf component without a default constructor?

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  • Why doesn't Visual Studio show an exception message when my exception occurs in a static constructor

    - by Tim Goodman
    I'm running this C# code in Visual Studio in debug mode: public class MyHandlerFactory : IHttpHandlerFactory { private static Dictionary<string, bool> myDictionary = new Dictionary<string, bool>(); static MyHandlerFactory() { myDictionary.Add("someKey",true); myDictionary.Add("someKey",true); // fails due to duplicate key } } Outside of the static constructor, when I get to the line with the error Visual Studio highlights it and pops up a message about the exception. But in the static constructor I get no such message. I am stepping through line-by-line, so I know that I'm getting to that line and no further. Why is this? (I have no idea if that fact that my class implements IHttpHandlerFactory matters, but I included it just in case.) This is VS2005, .Net 2.0

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  • C# Constructor Question

    - by Vaccano
    I have a constructor question for C#. I have this class: public partial class Signature : Form, ISignature { private readonly SignatureMediator mediator; public Signature(SignatureMediator mediator) { this.mediator = mediator; InitializeComponent(); } .... more stuff } I want to construct this class like this: public SignatureMediator(int someValue, int otherValue, int thirdValue) : this(new Signature(this), someValue, otherValue, thirdValue) // This is not allowed --^ { // I don't see anyway to get this in to the ":this" part. //Signature signature = new Signature(this); } public SignatureMediator(ISignature form, int someValue, int otherValue, int thirdValue) { SigForm = form; SomeValue= someValue; OtherValue= otherValue; ThirdValue= thirdValue; } The : this( new SignatureThis(this) is not allowed (the this used in the constructor is not allowed). Is there anyway to set this up without duplicating the assignment of the int values?

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  • Activator.CreateInstance(Type) for a type without parameterless constructor

    - by Seb
    Reading existing code at work, I wondered how come this could work. I have a class defined in an assembly : [Serializable] public class A { private readonly string _name; private A(string name) { _name = name; } } And in another assembly : public void f(Type t) { object o = Activator.CreateInstance(t); } and that simple call f(typeof(A)) I expected an exception about the lack of a parameterless constructor because AFAIK, if a ctor is declared, the compiler isn't supposed to generate the default public parameterless constructor. This code runs under .NET 2.0.

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  • Class Type Expected error on TableAdapter constructor

    - by Chris Franz
    I am using Delphi Prism to connect to an Advantage Database Server. I created a connection using the server explorer to the database. I added a dataset object to my project and added a table to the dataset. Everything works fine in the IDE, however, I get an error in the generated designer code on the table adapter constructor. The error is: (PE26) Class type expected. Here is the generated code: { Presidents.PresidentsTableAdapters.USPRESIDENTSTableAdapter } constructor Presidents.PresidentsTableAdapters.USPRESIDENTSTableAdapter; begin self.ClearBeforeFill := true; end;

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  • Constructor or Explicit cast

    - by Felan
    In working with Linq to Sql I create a seperate class to ferry data to a web page. To simplify creating these ferry objects I either use a specialized constructor or an explicit conversion operator. I have two questions. First which approach is better from a readibility perspective? Second while the clr code that is generated appeared to be the same to me, are there situations where one would be treated different than the other by the compiler (in lambda's or such). Example code (DatabaseFoo uses specialized constructor and BusinessFoo uses explicit operator): public class DatabaseFoo { private static int idCounter; // just to help with generating data public int Id { get; set; } public string Name { get; set; } public DatabaseFoo() { Id = idCounter++; Name = string.Format("Test{0}", Id); } public DatabaseFoo(BusinessFoo foo) { this.Id = foo.Id; this.Name = foo.Name; } } public class BusinessFoo { public int Id { get; set; } public string Name { get; set; } public static explicit operator BusinessFoo(DatabaseFoo foo) { return FromDatabaseFoo(foo); } public static BusinessFoo FromDatabaseFoo(DatabaseFoo foo) { return new BusinessFoo {Id = foo.Id, Name = foo.Name}; } } public class Program { static void Main(string[] args) { Console.WriteLine("Creating the initial list of DatabaseFoo"); IEnumerable<DatabaseFoo> dafoos = new List<DatabaseFoo>() { new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo()}; foreach(DatabaseFoo dafoo in dafoos) Console.WriteLine(string.Format("{0}\t{1}", dafoo.Id, dafoo.Name)); Console.WriteLine("Casting the list of DatabaseFoo to a list of BusinessFoo"); IEnumerable<BusinessFoo> bufoos = from x in dafoos select (BusinessFoo) x; foreach (BusinessFoo bufoo in bufoos) Console.WriteLine(string.Format("{0}\t{1}", bufoo.Id, bufoo.Name)); Console.WriteLine("Creating a new list of DatabaseFoo by calling the constructor taking BusinessFoo"); IEnumerable<DatabaseFoo> fufoos = from x in bufoos select new DatabaseFoo(x); foreach(DatabaseFoo fufoo in fufoos) Console.WriteLine(string.Format("{0}\t{1}", fufoo.Id, fufoo.Name)); } }

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  • mockito mock a constructor with parameter

    - by Shengjie
    I have a class as below: public class A { public A(String test) { bla bla bla } public String check() { bla bla bla } } The logic in the constructor A(String test) and check() are the things I am trying to mock. I want any calls like: new A($$$any string$$$).check() returns a dummy string "test". I tried: A a = mock(A.class); when(a.check()).thenReturn("test"); String test = a.check(); // to this point, everything works. test shows as "tests" whenNew(A.class).withArguments(Matchers.anyString()).thenReturn(rk); // also tried: //whenNew(A.class).withParameterTypes(String.class).withArguments(Matchers.anyString()).thenReturn(rk); new A("random string").check(); // this doesn't work But it doesn't seem to be working. new A($$$any string$$$).check() is still going through the constructor logic instead of fetch the mocked object of A.

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  • ASP.NET MVC - ASPX with non-default constructor

    - by bh213
    Is it possible for a ASPX view (in ASP.NET MVC) to have non-default constructor AND use this constructor when creating this view? Example - Page will inherit from this class: public class ViewPageWithHelper<TModel> : System.Web.Mvc.ViewPage<TModel> where TModel : class { public ViewPageWithHelper(Helpers helpers) { Helpers = helpers; } protected Helpers Helpers { get; private set; } } ASPX view: <%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="MyInjectedViewPage<MyModel>" %> <% Helpers.XXXX %> Now, I'd like to inject Helpers into view somehow - automatically. Ideas?

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  • Constructor type not found

    - by WaffleTop
    Hello, What I am doing: I am taking the Microsoft Enterprise Library 4.1 and attempting to expand upon it using a few derived classes. I have created a MyLogEntry, MyFormatter, and MyTraceListener which derive from their respective base classes when you remove the "My" from their names. What my problem is: Everything compiles fine. When I go to run a test using Logger.Write(logEntry) it errors right after it initializes MyTraceListener with an error message: "The current build operation (... EnterpriseLibrary.Logging.LogWriter, null]) failed: Constructor on type 'MyLogging.MyFormatter' not found. (Strategy type ConfiguredObjectStrategy, index 2) I figured it was something to do with the constructor so I tried removing it, add it, and adding a call to the base class LogFormatter. Nothing has worked. Does anyone have insight into this problem? Is it maybe a reference issue? Bad App.config configuration? Thank you in advance

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  • How to use this Color's constructor? Java

    - by MaxMackie
    According to Oracle's site, the class Color has a constructor that accepts a single int value which represents an RGB value. http://download.oracle.com/javase/1.4.2/docs/api/java/awt/Color.html#Color(int) An RGB color is actually three different numbers ranging from 0-255. So combining them together to make one int would look like this: White 255,255,255 White 255255255 Right? So I pass this to the constructor and get a vibrant teal color. What am I doing wrong? What haven't I understood?

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  • Flash AS3: automate property assignment to new instance from arguments in constructor

    - by matt lohkamp
    I like finding out about tricky new ways to do things. Let's say you've got a class with a property that gets set to the value of an argument in the constructor, like so: package{ public class SomeClass{ private var someProperty:*; public function SomeClass(_someProperty:*):void{ someProperty = _someProperty; } } } That's not exactly a hassle. But imagine you've got... I don't know, five properties. Ten properties, maybe. Rather then writing out each individual assignment, line by line, isn't there a way to loop through the constructor's arguments and set the value of each corresponding property on the new instance accordingly? I don't think that the ...rest or arguments objects will work, since they only keep an enumerated list of the arguments, not the argument names - I'm thinking something like this would be better: for(var propertyName:String in argsAsAssocArray){this[propertyName] = argsAsAssocArray[propertyName];} ... does something like this exist?

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  • std::string constructor corrupts pointer

    - by computergeek6
    I have an Entity class, which contains 3 pointers: m_rigidBody, m_entity, and m_parent. Somewhere in Entity::setModel(std::string model), it's crashing. Apparently, this is caused by bad data in m_entity. The weird thing is that I nulled it in the constructor and haven't touched it since then. I debugged it and put a watchpoint on it, and it comes up that the m_entity member is being changed in the constructor for std::string that's being called while converting a const char* into an std::string for the setModel call. I'm running on a Mac, if that helps (I think I remember some problem with std::string on the Mac). Any ideas about what's going on?

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  • C++ Why is the copy constructor implicitly called?

    - by ShaChris23
    Why is the Child class's copy constructor called in the code below? I mean, it automatically converts Base to Child via the Child copy constructor. The code below compiles, but shouldn't it not compile since I haven't provided bool Child::operator!=(Base const&)? class Base { }; class Child : public Base { public: Child() {} Child(Base const& base_) : Base(base_) { std::cout <<"should never called!"; } bool operator!=(Child const&) { return true; } }; void main() { Base base; Child child; if(child != base) std::cout << "not equal"; else std::cout << "equal"; }

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  • Static constructor can run after the non-static constructor. Is this a compiler bug?

    - by Joe H
    The output from the following program is: Non-Static Static Non-Static Is this a compiler bug? I expected: Static Non-Static Non-Static because I thought the static constructor was ALWAYS called before the non-static constructor. I tested this with Visual Studio 2010 using both .net 3.5 and .net 4.0. using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace StaticConstructorBug { class Program { static void Main(string[] args) { var mc = new MyClass(); Console.ReadKey(); } } public class MyClass { public MyClass() { Console.WriteLine("Non-static"); } static MyClass() { Console.WriteLine("Static"); } public static MyClass aVar = new MyClass(); } }

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  • C++ Scoping and ambiguity in constructor overloads

    - by loarabia
    I've tried the following code snippet in 3 different compilers (G++, clang++, CL.exe) and they all report to me that they cannot disambiguate the overloaded constructors. Now, I know how I could modify the call to the constructor to make it pick one or the other (either make explicit that the second argument is a unsigned literal value or explicitly cast it). However, I'm curious why the compiler would be attempting to choose between constructors in the first place given that one of the constructors is private and the call to the constructor is happening in the main function which should be outside the class's scope. Can anyone enlighten me? class Test { private: Test(unsigned int a, unsigned int *b) { } public: Test(unsigned int a, unsigned int b) { } }; int main() { Test t1 = Test(1,0); // compiler is confused }

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  • Why do we need a private constructor?

    - by isthatacode
    if a class has a private constructor then it cant be instantiated. so, if i dont want my class to be instantiated and still use it, then i can make it static. what is the use of a private constructor ? Also its used in singleton class, except that, is there any othe use ? (Note : The reason i am excuding the singleton case above is because I dont understand why do we need a singleton at all ? when there is a static class availble. You may not answer for my this confusion in the question. )

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