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  • Constructor overriding

    - by demas
    I have a library with a class: class One def initialize puts "one initialize" end end I can not change the declaration and difinition of this class. I need create new class with my own constructor. Like this: class Two < One def initialize(some) puts some super end end one = One.new one = Two.new("thing") But when I launch code I got error: [[email protected]][~/temp]% ruby test.rb one initialize thing test.rb:10:in `initialize': wrong number of arguments (1 for 0) (ArgumentError) from test.rb:15:in `new' from test.rb:15:in `<main>'

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  • Attribute class not calling constructor

    - by Coppermill
    I have created an Attribute, call MyAttribute, which is performing some security and for some reason the Constructor is not being fired, any reason why? public class Driver { // Entry point of the program public static void Main(string[] Args) { Console.WriteLine(SayHello1("Hello to Me 1")); Console.WriteLine(SayHello2("Hello to Me 2")); Console.ReadLine(); } [MyAttribute("hello")] public static string SayHello1(string str) { return str; } [MyAttribute("Wrong Key, should fail")] public static string SayHello2(string str) { return str; } } [AttributeUsage(AttributeTargets.Method)] public class MyAttribute : Attribute { public MyAttribute(string VRegKey) { if (VRegKey == "hello") { Console.WriteLine("Aha! You're Registered"); } else { throw new Exception("Oho! You're not Registered"); }; } }

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  • how to deal a constructor with an array in Perl

    - by superstar
    whats the difference between these two 'new' constructors in perl? 1) sub new { my $class = shift; my $self = {}; $self->{firstName} = undef; $self->{lastName} = undef; $self->{PEERS} = []; bless ($self, $class); return $self; } 2) sub new { my $class = shift; my $self = { _firstName => shift, _lastName => shift, _ssn => shift, }; bless $self, $class; return $self; } I am using the 2nd one so far, but i need to implement the arrays in perl? can you suggest a way to do it with the 2nd 'new' constructor and how can we use get and set methods on those array variables?

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  • Factory Method pattern and public constructor

    - by H4mm3rHead
    Hi, Im making a factory method that returns new instances of my objects. I would like to prevent anyone using my code from using a public constructor on my objects. Is there any way of doing this? How is this typically accomplished: public abstract class CarFactory { public abstract ICar CreateSUV(); } public class MercedesFactory : CarFactory { public override ICar CreateSUV() { return new Mercedes4WD(); } } I then would like to limit/prevent the other developers (including me in a few months) from making an instance of Mercedes4WD. But make them call my factory method. How to?

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  • Constructor invocation returned null: what to do?

    - by strager
    I have code which looks like: private static DirectiveNode CreateInstance(Type nodeType, DirectiveInfo info) { var ctor = nodeType.GetConstructor(new[] { typeof(DirectiveInfo) }); if(ctor == null) { throw new MissingMethodException(nodeType.FullName, "ctor"); } var node = ctor.Invoke(new[] { info }) as DirectiveNode; if(node == null) { // ???; } return node; } I am looking for what to do (e.g. what type of exception to throw) when the Invoke method returns something which isn't a DirectiveNode or when it returns null (indicated by // ??? above). (By the method's contract, nodeType will always describe a subclass of DirectiveNode.) I am not sure when calling a constructor would return null, so I am not sure if I should handle anything at all, but I still want to be on the safe side and throw an exception if something goes wrong.

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  • Singleton constructor question

    - by gillyb
    Hi, I created a Singleton class in c#, with a public property that I want to initialize when the Singleton is first called. This is the code I wrote : public class BL { private ISessionFactory _sessionFactory; public ISessionFactory SessionFactory { get { return _sessionFactory; } set { _sessionFactory = value; } } private BL() { SessionFactory = Dal.SessionFactory.CreateSessionFactory(); } private object thisLock = new object(); private BL _instance = null; public BL Instance { get { lock (thisLock) { if (_instance == null) { _instance = new BL(); } return _instance; } } } } As far as I know, when I address the Instance BL object in the BL class for the first time, it should load the constructor and that should initialize the SessionFactory object. But when I try : BL.Instance.SessionFactory.OpenSession(); I get a Null Reference Exception, and I see that SessionFactory is null... why?

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  • Constructor invokation returned null: what to do?

    - by strager
    I have code which looks like: private static DirectiveNode CreateInstance(Type nodeType, DirectiveInfo info) { var ctor = nodeType.GetConstructor(new[] { typeof(DirectiveInfo) }); if(ctor == null) { throw new MissingMethodException(nodeType.FullName, "ctor"); } var node = ctor.Invoke(new[] { info }) as DirectiveNode; if(node == null) { // ???; } return node; } I am looking for what to do (e.g. what type of exception to throw) when the Invoke method returns something which isn't a DirectiveNode or when it returns null (indicated by // ??? above). (By the method's contract, nodeType will always describe a subclass of DirectiveNode.) I am not sure when calling a constructor would return null, so I am not sure if I should handle anything at all, but I still want to be on the safe side and throw an exception if something goes wrong.

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  • Is this class + constructor definition pattern overly redundant?

    - by Protector one
    I often come across a pattern similar to this: class Person { public string firstName, lastName; public Person(string firstName, string lastName) { this.firstName = firstName; this.lastName = lastName; } } This feels overly redundant (I imagine typing "firstName" once, instead of thrice could be enough…), but I can't think of a proper alternative. Any ideas? Maybe I just don't know about a certain design pattern I should be using here? Edit - I think I need to elaborate a little. I'm not asking how to make the example code "better", but rather, "shorter". In its current state, all member names appear 3 times (declaration, initialization, constructor arguments), and it feels rather redundant. So I'm wondering if there is a pattern (or semantic sugar) to get (roughly) the same behavior, but with less bloat. I apologize for being unclear initially.

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  • How to extract terms of specific data constructor from a list in Haskell

    - by finnsson
    A common problem I got in Haskell is to extract all terms in a list belonging to a specific data constructor and I'm wondering if there are any better ways than the way I'm doing it at the moment. Let's say you got data Foo = Bar | Goo , the list foos = [Bar, Goo, Bar, Bar, Goo] and wish to extract all Goos from foos. At the moment I usually do something like goos = [Goo | Goo <- foos] and all is well. The problem is when Goo got a bunch of fields and I'm forced to write something like goos = [Goo a b c d e f | Goo a b c d e f <- foos] which is far from ideal. How you do usually handle this problem?

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  • python: calling constructor from dictionary?

    - by Jason S
    I'm not quite sure of the terminology here so please bear with me.... Let's say I have a constructor call like this: machineSpecificEnvironment = Environment( TI_C28_ROOT = 'C:/appl/ti/ccs/4.1.1/ccsv4/tools/compiler/c2000', JSDB = 'c:/bin/jsdb/jsdb.exe', PYTHON_PATH = 'c:/appl/python/2.6.4', ) except I would like to replace that by an operation on a dictionary provided to me: keys = {'TI_C28_ROOT': 'C:/appl/ti/ccs/4.1.1/ccsv4/tools/compiler/c2000', 'JSDB': 'c:/bin/jsdb/jsdb.exe', 'PYTHON_PATH': 'c:/appl/python/2.6.4'} machineSpecificEnvironment = Environment( ... what do I put here? it needs to be a function of "keys" ... ) How can I do this?

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  • Result of expression 'xxxx' is not a constructor in JS

    - by Pselus
    Trying to create an object in Javascript (for Appcelerator/Titanium). The "object" is defined like this: function server () { this.cacheimages = 0; this.login = ""; this.name = ""; this.root = ""; this.signup = ""; this.useimages = 0; this.userexists = ""; this.isdefault = 0; return this; } In the same file, in another function when I run this line: var server = new server(); I get the error Result of expression 'server' is not a constructor. I have tried it with and without the "return" line, neither work. What am I doing wrong?

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  • How to deal with constructor argument names?

    - by Bane
    Say I have a class that has some properties, like x, y, width and height. In its constructor, I couldn't do this: class A { public: A(int, int, int, int); int x; int y; int width; int height; }; //Wrong and makes little sense name-wise: A::A(int x, int y, int width, int height) { x = x; y = y; width = width; height = height; } First of all, this doesn't really make sense. Second, x, y, width and height become some weird values (-1405737648) when compiled using g++. It does work, however, if I append "a" to the argument names. What is the optimal way of solving these naming conflicts?

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  • Running a method after the constructor of any derived class

    - by Alexey Romanov
    Let's say I have a Java class abstract class Base { abstract void init(); ... } and I know every derived class will have to call init() after it's constructed. I could, of course, simply call it in the derived classes' constructors: class Derived1 extends Base { Derived1() { ... init(); } } class Derived2 extends Base { Derived2() { ... init(); } } but this breaks "don't repeat yourself" principle rather badly (and there are going to be many subclasses of Base). Of course, the init() call can't go into the Base() constructor, since it would be executed too early. Any ideas how to bypass this problem? I would be quite happy to see a Scala solution, too.

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  • No Parameterless Constructor defined for - ViewModel with UOW

    - by TheVillageIdiot
    I have a view model class which uses UnitOfWork to some database operations like fetching of items to create select lists and IPrincipal for some auditing (like modified by etc.). It cannot work without this UOW. I have configured my web site to use Ninject to inject UOW into Controllers. From controller I pass this UOW when creating view model. But when performing POST operation I am getting No parameterless constructor defined for this object. I have few SelectList type of properties which I have excluded with Bind attribute. How can I overcome this problem? Can I configure Ninject to create the objects of this type and make ModelBinder use it?

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  • C++: Avoid .cpp files with only an empty (de)constructor

    - by Martijn Courteaux
    Hi, When I have a header file like this: #ifndef GAMEVIEW_H_ #define GAMEVIEW_H_ #include <SDL/SDL.h> class GameView { public: GameView(); virtual ~GameView(); virtual void Update() = 0; virtual void Render(SDL_Surface* buffer) = 0; }; #endif /* GAMEVIEW_H_ */ I need to create a .cpp file like this: #include "GameView.h" GameView::~GameView() { } GameView::GameView() { } This is a bit stupid. Just a .cpp file for an empty constructor and deconstructor. I want to implement that method simply in the header file. That is much cleaner. How to do this?

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  • C# Generic List constructor gives me a MethodAccessException

    - by evilfred
    Hi, I make a list in my code like so: List<IConnection> connections = new List<IConnection>(); where IConnection is my own interface. This is in a .NET 2.0 executable. If I run the code on my machine (with lots of .Net versions installed) it works fine. If I run it on my test machine (which only has .NET 3.5 SP1 installed) then I get a MethodAccessException in the System.Collections.Generic.List constructor. Any ideas what could be going wrong?

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  • Call a C++ constructor from an Objective C class

    - by syvex
    How can I call a C++ constructor from inside an Objective C class? class CppClass { public: CppClass(int arg1, const std::string& arg2): _arg1(arg1), _arg2(arg2) { } // ... private: int _arg1; std::string _arg2; }; @interface ObjC: NSObject { CppClass _cppClass; } @end @implementation ObjC - (id)init { self = [super init]; if ( self ) { // what is the syntax to call CppClass::CppClass(5, "hello") on _cppClass? } return self; } @end

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  • Passing System classes as constructor parameters

    - by mcl
    This is probably crazy. I want to take the idea of Dependency Injection to extremes. I have isolated all System.IO-related behavior into a single class so that I can mock that class in my other classes and thereby relieve my larger suite of unit tests of the burden of worrying about the actual file system. But the File IO class I end up with can only be tested with integration tests, which-- of course-- introduces complexity I don't really want to deal with when all I really want to do is make sure my FileIO class calls the correct System.IO stuff. I don't need to integration test System.IO. My FileIO class is doing more than simply wrapping System.IO functions, every now and then it does contain some logic (maybe this is the problem?). So what I'd like is to be able to test my File IO class to ensure that it makes the correct system calls by mocking the System.IO classes themselves. Ideally this would be as easy as having a constructor like so: public FileIO( System.IO.Directory directory, System.IO.File file, System.IO.FileStream fileStream ) { this.Directory = directory; this.File = file; this.FileStream = fileStream; } And then calling in methods like: public GetFilesInFolder(string folderPath) { return this.Directory.GetFiles(folderPath) } But this doesn't fly since the System.IO classes in question are static classes. As far as I can tell they can neither be instantiated in this way or subclassed for the purposes of mocking.

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  • C++ Add this pointer to a container by calling it in base class constructor

    - by vivekeviv
    class Base { public: Base (int a, int b); private: int a,b; }; class Derived1 { public: Derived1():base(1,2){} }; similarly Derived2, Derived 3 which doesnt contain any data members on its own Now i need to contain these derived objects in a singleton, so i was thinking to call this in base constructor like Base::Base(int a, int b) { CBaseMgr::GetInstance()->AddtoVector(this); } so now if i construct Derived d1, d2, d3 etc. will the Singleton's container contain all derived objects? My doubt is can i do this adding of objects to container in base ctor or should i do in derived ctor.?

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  • C++ Declaring an uninitialized variable without a null constructor

    - by xbonez
    Consider the DUPoint class, whose declaration appears below. Assume this code appears in a file named DUPoint.h: #include <string> class DUPoint { public: DUPoint (int x, int y); int getX () const; int getY () const; void setX (int x); void setY (int y); void print(); private: int x_; int y_; }; Is it true that you cannot declare an uninitialized DUPoint variable with a statement such as DUPoint P; using this class as currently configured because it has no null constructor?

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  • objective-c - calling one constructor from another

    - by synic
    Say you had the following two constructors: - (id)initWithTitle:(NSString *)title; - (id)initWithTitle:(NSString *)title page:(NSString *)page; The second constructor is no different from the first, except that it sets up the member variable "page". Since it basically has to do the same thing, is there a way to call the first one from the second one to reduce code duplication, or do you have to set up a third method to do the common tasks? I'm talking about something similar to this, though I doubt this will work: - (id)initWithTitle:(NSString *)_title { if(self = [super init]) { self.title = _title; } return self; } - (id)initWithTitle:(NSString *)_title page:(NSString *)_page { if(self = [self initWithTitle:_title]) { self.page = _page; } return self; }

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  • C# Generic new() constructor problem

    - by LB
    I'm trying to create a new object of type T via its constructor when adding to the list. I'm getting a compile error: The correct error message is: 'T': cannot provide arguments when creating an instance of a variable But it does! Any ideas? public static string GetAllItems<T>(...) where T : new() { ... List<T> tabListItems = new List<T>(); foreach (ListItem listItem in listCollection) { tabListItems.Add(new T(listItem)); // error here. } ... }

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  • Call subclass constructor from abstract class in Java

    - by Joel
    public abstract class Parent { private Parent peer; public Parent() { peer = new ??????("to call overloaded constructor"); } public Parent(String someString) { } } public class Child1 extends parent { } public class Child2 extends parent { } When I construct an instance of Child1, I want a "peer" to automatically be constructed which is also of type Child1, and be stored in the peer property. Likewise for Child2, with a peer of type Child2. The problem is, on the assignment of the peer property in the parent class. I can't construct a new Child class by calling new Child1() because then it wouldn't work for Child2. How can I do this? Is there a keyword that I can use that would refer to the child class? Something like new self()?

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  • Spring Test / JUnit problem - unable to load application context

    - by HDave
    I am using Spring for the first time and must be doing something wrong. I have a project with several Bean implementations and now I am trying to create a test class with Spring Test and JUnit. I am trying to use Spring Test to inject a customized bean into the test class. Here is my test-applicationContext.xml: <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="............."> <bean id="MyUuidFactory" class="com.myapp.UuidFactory" scope="singleton" > <property name="typeIdentifier" value="CLS" /> </bean> <bean id="ThingyImplTest" class="com.myapp.ThingyImplTest" scope="singleton"> <property name="uuidFactory"> <idref local="MyUuidFactory" /> </property> </bean> </beans> The injection of MyUuidFactory instance goes along with the following code from within the test class: private UuidFactory uuidFactory; public void setUuidFactory(UuidFactory uuidFactory) { this.uuidFactory = uuidFactory; } However, when I go to run the test (in Eclipse or command line) I get the following error (stack trace omitted for brevity): Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'MyImplTest' defined in class path resource [test-applicationContext.xml]: Initialization of bean failed; nested exception is org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'java.lang.String' to required type 'com.myapp.UuidFactory' for property 'uuidFactory'; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [com.myapp.UuidFactory] for property 'uuidFactory': no matching editors or conversion strategy found Funny thing is, the Eclipse/Spring XML editor shows errors of I misspell any of the types or idrefs. If I leave the bean in, but comment out the dependency injection, everything work until I get a NullPointerException while running the test...which makes sense.

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  • Are Parameters really enough to prevent Sql injections?

    - by Rune Grimstad
    I've been preaching both to my colleagues and here on SO about the goodness of using parameters in SQL queries, especially in .NET applications. I've even gone so far as to promise them as giving immunity against SQL injection attacks. But I'm starting to wonder if this really is true. Are there any known SQL injection attacks that will be successfull against a parameterized query? Can you for example send a string that causes a buffer overflow on the server? There are of course other considerations to make to ensure that a web application is safe (like sanitizing user input and all that stuff) but now I am thinking of SQL injections. I'm especially interested in attacks against MsSQL 2005 and 2008 since they are my primary databases, but all databases are interesting. Edit: To clarify what I mean by parameters and parameterized queries. By using parameters I mean using "variables" instead of building the sql query in a string. So instead of doing this: SELECT * FROM Table WHERE Name = 'a name' We do this: SELECT * FROM Table WHERE Name = @Name and then set the value of the @Name parameter on the query / command object.

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