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  • What are the advantages of learning Go?

    - by Pangea
    What is so unique about Go? Over the 11 years of my career I've learnt Pascal, C, C++, COBOL and then Java. I always felt that going from C to C++ to Java was a incremental and value added progression. Now I see a proliferation of functional programming languages and I understand the benefit of learning few of them (like actors in scala etc). Now I was going through the Go programming language and was wondering why would I want to learn this? Is this going to simplify how I have been writing the code? What are its use cases? How can I make a case to promote it in my team? What is the next programming language that a Java team that builds business applications like us can benefit from? Appreciate your comments on this.

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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 determine which inheriting class is using an abstract class's methods.

    - by Kin
    In my console application have an abstract Factory class "Listener" which contains code for listening and accepting connections, and spawning client classes. This class is inherited by two more classes (WorldListener, and MasterListener) that contain more protocol specific overrides and functions. I also have a helper class (ConsoleWrapper) which encapsulates and extends System.Console, containing methods for writing to console info on what is happening to instances of the WorldListener and MasterListener. I need a way to determine in the abstract ListenerClass which Inheriting class is calling its methods. Any help with this problem would be greatly appreciated! I am stumped :X Simplified example of what I am trying to do. abstract class Listener { public void DoSomething() { if(inheriting class == WorldListener) ConsoleWrapper.WorldWrite("Did something!"); if(inheriting class == MasterListener) ConsoleWrapper.MasterWrite("Did something!"); } } public static ConsoleWrapper { public void WorldWrite(string input) { System.Console.WriteLine("[World] {0}", input); } } public class WorldListener : Listener { public void DoSomethingSpecific() { ConsoleWrapper.WorldWrite("I did something specific!"); } } public void Main() { new WorldListener(); new MasterListener(); } Expected output [World] Did something! [World] I did something specific! [Master] Did something! [World] I did something specific!

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  • How should I pass the translated text to my object in my multilingual application?

    - by boatingcow
    Up until now, I have maintained a 'dictionary' table in my database, for example: +-----------+---------------------------------------+-----------------------------------------------+--------+ | phrase | en | fr | etc... | +-----------+---------------------------------------+-----------------------------------------------+--------+ | generated | Generated in %1$01.2f seconds at %2$s | Créée en %1$01.2f secondes à %2$s aujourd'hui | ... | | submit | Submit... | Envoyer... | ... | +-----------+---------------------------------------+-----------------------------------------------+--------+ I'll then select all rows from the database for the column that matches the locale we're interested in (or read the cache from a file to speed db lookup) and dump the dictionary into an array called $lng. Then I'll have HTML helper objects like this in my view: $html->input(array('type' => 'submit', 'value' => $lng['submit'], etc...)); ... $html->div(array('value' => sprintf($lng['generated'], $generated, date('H:i')), etc...)); The translations can appear in PDF, XLS and AJAX responses too. The problem with my approach so far is that I now have loads of global $lng; in every class where there is a function that spits out UI code.. How do other people get the translation into the object? Is it one scenario where globals aren't actually that bad? Would it be madness to create a class with accessors when the dictionary terms are all static?

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  • Designing different Factory classes (and what to use as argument to the factories!)

    - by devoured elysium
    Let's say we have the following piece of code: public class Event { } public class SportEvent1 : Event { } public class SportEvent2 : Event { } public class MedicalEvent1 : Event { } public class MedicalEvent2 : Event { } public interface IEventFactory { bool AcceptsInputString(string inputString); Event CreateEvent(string inputString); } public class EventFactory { private List<IEventFactory> factories = new List<IEventFactory>(); public void AddFactory(IEventFactory factory) { factories.Add(factory); } //I don't see a point in defining a RemoveFactory() so I won't. public Event CreateEvent(string inputString) { try { //iterate through all factories. If one and only one of them accepts //the string, generate the event. Otherwise, throw an exception. return factories.Single(factory => factory.AcceptsInputString(inputString)).CreateEvent(inputString); } catch (InvalidOperationException e) { throw new InvalidOperationException("No valid factory found to generate this kind of Event!", e); } } } public class SportEvent1Factory : IEventFactory { public bool AcceptsInputString(string inputString) { return inputString.StartsWith("SportEvent1"); } public Event CreateEvent(string inputString) { return new SportEvent1(); } } public class MedicalEvent1Factory : IEventFactory { public bool AcceptsInputString(string inputString) { return inputString.StartsWith("MedicalEvent1"); } public Event CreateEvent(string inputString) { return new MedicalEvent1(); } } And here is the code that runs it: static void Main(string[] args) { EventFactory medicalEventFactory = new EventFactory(); medicalEventFactory.AddFactory(new MedicalEvent1Factory()); medicalEventFactory.AddFactory(new MedicalEvent2Factory()); EventFactory sportsEventFactory = new EventFactory(); sportsEventFactory.AddFactory(new SportEvent1Factory()); sportsEventFactory.AddFactory(new SportEvent2Factory()); } I have a couple of questions: Instead of having to add factories here in the main method of my application, should I try to redesign my EventFactory class so it is an abstract factory? It'd be better if I had a way of not having to manually add EventFactories every time I want to use them. So I could just instantiate MedicalFactory and SportsFactory. Should I make a Factory of factories? Maybe that'd be over-engineering? As you have probably noticed, I am using a inputString string as argument to feed the factories. I have an application that lets the user create his own events but also to load/save them from text files. Later, I might want to add other kinds of files, XML, sql connections, whatever. The only way I can think of that would allow me to make this work is having an internal format (I choose a string, as it's easy to understand). How would you make this? I assume this is a recurrent situation, probably most of you know of any other more intelligent approach to this. I am then only looping in the EventFactory for all the factories in its list to check if any of them accepts the input string. If one does, then it asks it to generate the Event. If you find there is something wrong or awkward with the method I'm using to make this happen, I'd be happy to hear about different implementations. Thanks! PS: Although I don't show it in here, all the different kind of events have different properties, so I have to generate them with different arguments (SportEvent1 might have SportName and Duration properties, that have to be put in the inputString as argument).

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  • How to fetch populated associated models in CakePHP when calling read()

    - by Code Commander
    I have the following Models: class Site extends AppModel { public $name = "Site"; public $useTable = "site"; public $primaryKey = "id"; public $displayField = 'name'; public $hasMany = array('Item' => array('foreignKey' => 'siteId')); public function canView($userId, $isAdmin = false) { if($isAdmin) { return true; } return array_key_exists($this->id, $allowedSites); } } and class Item extends AppModel { public $name = "Item"; public $useTable = "item"; public $primaryKey = "id"; public $displayField = 'name'; public $belongsTo = array('Site' => array('foreignKey' => 'siteId')); public function canView($userId, $isAdmin = false) { // My problem appears to be the next line: return $this->Site->canView($userId, $isAdmin); } } In my controller I am doing something like this: $result = $this->Item->read(null, $this->request->id); // Verify permissions if(!$this->Item->canView($this->Session->read('userId'), $this->Session->read('isAdmin'))) { $this->httpCodes(403); die('Permission denied.'); } I notice that in Item->canView() $this->data['Site'] is populated with the column data from the site table. But it merely an array and not an object. On the other hand $this->Site is a Site object, but it has not been populated with the column data from the site table like $this->data. What is the proper way to have CakePHP get the associated model as the object and containing the data? Or am I going about this all wrong? Thanks!

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  • C++ Linked List - Reading data from a file with a sentinel

    - by Nick
    So I've done quite a bit of research on this and can't get my output to work correctly. I need to read in data from a file and have it stored into a Linked List. The while loop used should stop once it hits the $$$$$ sentinel. Then I am to display the data (by searching by ID Number[user input]) I am not that far yet I just want to properly display the data and get it read in for right now. My problem is when it displays the data is isn't stopping at the $$$$$ (even if I do "inFile.peek() != EOF and omit the $$$$$) I am still getting an extra garbage record. I know it has something to do with my while loop and how I am creating a new Node but I can't get it to work any other way. Any help would be appreciated. students.txt Nick J Cooley 324123 60 70 80 90 Jay M Hill 412254 70 80 90 100 $$$$$ assign6.h file #pragma once #include <iostream> #include <string> using namespace std; class assign6 { public: assign6(); // constructor void displayStudents(); private: struct Node { string firstName; string midIni; string lastName; int idNum; int sco1; //Test score 1 int sco2; //Test score 2 int sco3; //Test score 3 int sco4; //Test score 4 Node *next; }; Node *head; Node *headPtr; }; assign6Imp.cpp // Implementation File #include "assign6.h" #include <fstream> #include <iostream> #include <string> using namespace std; assign6::assign6() //constructor { ifstream inFile; inFile.open("students.txt"); head = NULL; head = new Node; headPtr = head; while (inFile.peek() != EOF) //reading in from file and storing in linked list { inFile >> head->firstName >> head->midIni >> head->lastName; inFile >> head->idNum; inFile >> head->sco1; inFile >> head->sco2; inFile >> head->sco3; inFile >> head->sco4; if (inFile != "$$$$$") { head->next = NULL; head->next = new Node; head = head->next; } } head->next = NULL; inFile.close(); } void assign6::displayStudents() { int average = 0; for (Node *cur = headPtr; cur != NULL; cur = cur->next) { cout << cur->firstName << " " << cur->midIni << " " << cur->lastName << endl; cout << cur->idNum << endl; average = (cur->sco1 + cur->sco2 + cur->sco3 + cur->sco4)/4; cout << cur->sco1 << " " << cur->sco2 << " " << cur->sco3 << " " << cur->sco4 << " " << "average: " << average << endl; } }

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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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  • How to set default values to all wrong or null parameters of method?

    - by Roman
    At the moment I have this code (and I don't like it): private RenderedImage private RenderedImage getChartImage (GanttChartModel model, String title, Integer width, Integer height, String xAxisLabel, String yAxisLabel, Boolean showLegend) { if (title == null) { title = ""; } if (xAxisLabel == null) { xAxisLabel = ""; } if (yAxisLabel == null) { yAxisLabel = ""; } if (showLegend == null) { showLegend = true; } if (width == null) { width = DEFAULT_WIDTH; } if (height == null) { height = DEFAULT_HEIGHT; } ... } How can I improve it? I have some thoughts about introducing an object which will contain all these parameters as fields and then, maybe, it'll be possible to apply builder pattern. But still don't have clear vision how to implement that and I'm not sure that it's worth to be done. Any other ideas?

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  • How to maintain a pool of names ?

    - by Jacques René Mesrine
    I need to maintain a list of userids (proxy accounts) which will be dished out to multithreaded clients. Basically the clients will use the userids to perform actions; but for this question, it is not important what these actions are. When a client gets hold of a userid, it is not available to other clients until the action is completed. I'm trying to think of a concurrent data structure to maintain this pool of userids. Any ideas ? Would a ConcurrentQueue do the job ? Clients will dequeue a userid, and add back the userid when they are finished with it.

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  • What's the idiomatic way of inheriting data access functionality as well as object properties?

    - by Knut Arne Vedaa
    Suppose the following (slightly pseudo-code for brevity): class Basic { String foo; } class SomeExtension extends Basic { String bar; } class OtherExtension extends Basic { String baz; } class BasicService { Basic getBasic() { } } class SomeExtensionService extends BasicService { SomeExtension getSomeExtension() { } } class OtherExtensionService extends BasicService { OtherExtension getOtherExtension() { } } What would be the most idiomatic, elegant way to implement the get-() service methods with the most possible code reuse? Obviously you could do it like this: class BasicService { Basic getBasic() { Basic basic = new Basic(); basic.setFoo("some kind of foo"); return basic; } } class SomeExtensionService { SomeExtension getSomeExtension() { SomeExtension someExtension = new SomeExtension; Basic basic = getBasic(); someExtension.setFoo(basic.getFoo()); someExtension.setBar("some kind of bar"); return someExtension; } } But this would be ugly if Basic has a lot of properties, and also you only need one object, as SomeExtension already inherits Basic. However, BasicService can obviously not return a SomeExtension object. You could also have the get methods not create the object themselves, but create it at the outermost level and pass it to the method for filling in the properties, but I find that too imperative. (Please let me know if the question is confusingly formulated.)

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  • what's Static type safety ?

    - by symfony
    Static type safety – an integral property of languages of the family to which C++ belongs and valuable both for guaranteeing properties of a design and for providing runtime and space efficiency. Can someone illustrate by a demo? Thanks

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  • PHP - Concatenating objects and casting to string - bad idea?

    - by franko75
    Is it bad practice to concatenate objects when used in this context: $this->template->head .= new View('custom_javascript') This is the way i normally add extra css/js stuff to specific pages. I use an MVC structure where my basic html template has a $head variable which I set in my main Website_controller. I have used this approach for a while as it means I can just add bits and pieces of css/js stuff from whichever page/controller needs it. But having come across a problem in PHP 5.1.6 where the above code results in "Object ID #24", the result of toString() not being called i think, I am rethinking whether i should just fix this to work in PHP 5.1.6 or if i should rethink this approach in general. Any pointers appreciated!

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  • How can I add a field with an array value to my Perl object?

    - by superstar
    What's the difference between these two 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 second one so far, but I need to implement the PEERS array in the second one? How do I do it with the second constructor and how can we use get and set methods on those array variables?

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  • PHP 5.3: Late static binding doesn't work for properties when defined in parent class while missing in child class

    - by DavidPesta
    Take a look at this example, and notice the outputs indicated. <?php class Mommy { protected static $_data = "Mommy Data"; public static function init( $data ) { static::$_data = $data; } public static function showData() { echo static::$_data . "<br>"; } } class Brother extends Mommy { } class Sister extends Mommy { } Brother::init( "Brother Data" ); Sister::init( "Sister Data" ); Brother::showData(); // Outputs: Sister Data Sister::showData(); // Outputs: Sister Data ?> My understanding was that using the static keyword would refer to the child class, but apparently it magically applies to the parent class whenever it is missing from the child class. (This is kind of a dangerous behavior for PHP, more on that explained below.) I have the following two things in mind for why I want to do this: I don't want the redundancy of defining all of the properties in all of the child classes. I want properties to be defined as defaults in the parent class and I want the child class definition to be able to override these properties wherever needed. The child class needs to exclude properties whenever the defaults are intended, which is why I don't define the properties in the child classes in the above example. However, if we are wanting to override a property at runtime (via the init method), it will override it for the parent class! From that point forward, child classes initialized earlier (as in the case of Brother) unexpectedly change on you. Apparently this is a result of child classes not having their own copy of the static property whenever it isn't explicitly defined inside of the child class--but instead of throwing an error it switches behavior of static to access the parent. Therefore, is there some way that the parent class could dynamically create a property that belongs to the child class without it appearing inside of the child class definition? That way the child class could have its own copy of the static property and the static keyword can refer to it properly, and it can be written to take into account parent property defaults. Or is there some other solution, good, bad, or ugly?

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  • Constructor within a constructor

    - by Chiramisu
    Is this a bad idea? Does calling a generic private constructor within a public constructor create multiple instances, or is this a valid way of initializing class variables? Private Class MyClass Dim _msg As String Sub New(ByVal name As String) Me.New() 'Do stuff End Sub Sub New(ByVal name As String, ByVal age As Integer) Me.New() 'Do stuff End Sub Private Sub New() 'Initializer constructor Me._msg = "Hello StackOverflow" 'Initialize other variables End Sub End Class

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  • Constructor Overloading

    - by Mark Baker
    Normally when I want to create a class constructor that accepts different types of parameters, I'll use a kludgy overloading principle of not defining any args in the constructor definition: e.g. for an ECEF coordinate class constructor, I want it to accept either $x, $y and $z arguments, or to accept a single array argument containg x, y and z values, or to accept a single LatLong object I'd create a constructor looking something like: function __construct() { // Identify if any arguments have been passed to the constructor if (func_num_args() > 0) { $args = func_get_args(); // Identify the overload constructor required, based on the datatype of the first argument $argType = gettype($args[0]); switch($argType) { case 'array' : // Array of Cartesian co-ordinate values $overloadConstructor = 'setCoordinatesFromArray'; break; case 'object' : // A LatLong object that needs converting to Cartesian co-ordinate values $overloadConstructor = 'setCoordinatesFromLatLong'; break; default : // Individual Cartesian co-ordinate values $overloadConstructor = 'setCoordinatesFromXYZ'; break; } // Call the appropriate overload constructor call_user_func_array(array($this,$overloadConstructor),$args); } } // function __construct() I'm looking at an alternative: to provide a straight constructor with $x, $y and $z as defined arguments, and to provide static methods of createECEFfromArray() and createECEFfromLatLong() that handle all the necessary extraction of x, y and z; then create a new ECEF object using the standard constructor, and return that Which option is cleaner from an OO purists perspective?

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  • Using pointers to adjust global objects in objective-c

    - by Rob
    Ok, so I am working with two sets of data that are extremely similar, and at the same time, these data sets are both global NSMutableArrays within the object. data_set_one = [[NSMutableArray alloc] init]; data_set_two = [[NSMutableArray alloc] init]; Two new NSMutableArrays are loaded, which need to be added to the old, existing data. These Arrays are also global. xml_dataset_one = [[NSMutableArray alloc] init]; xml_dataset_two = [[NSMutableArray alloc] init]; To reduce code duplication (and because these data sets are so similar) I wrote a void method within the class to handle the data combination process for both Arrays: -(void)constructData:(NSMutableArray *)data fromDownloadArray:(NSMutableArray *)down withMatchSelector:(NSString *)sel_str Now, I have a decent understanding of object oriented programming, so I was thinking that if I were to invoke the method with the global Arrays in the data like so... [self constructData:data_set_one fromDownloadArray:xml_dataset_one withMatchSelector:@"id"]; Then the global NSMutableArrays (data_set_one) would reflect the changes that happen to "array" within the method. Sadly, this is not the case, data_set_one doesn't reflect the changes (ex: new objects within the Array) outside of the method. Here is a code snippet of the problem // data_set_one is empty // xml_dataset_one has a few objects [constructData:(NSMutableArray *)data_set_one fromDownloadArray:(NSMutableArray *)xml_dataset_one withMatchSelector:(NSString *)@"id"]; // data_set_one should now be xml_dataset_one, but when echoed to screen, it appears to remain empty And here is the gist of the code for the method, any help is appreciated. -(void)constructData:(NSMutableArray *)data fromDownloadArray:(NSMutableArray *)down withMatchSelector:(NSString *)sel_str { if ([data count] == 0) { data = down; // set data equal to downloaded data } else if ([down count] == 0) { // download yields no results, do nothing } else { // combine the two arrays here } } This project is not ARC enabled. Thanks for the help guys! Rob

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  • Transferring object from parent to child

    - by waiwai933
    I'm currently developing an Custom Application using the IP.Board framework, which is in PHP, which by default, creates a IPSMember object for the logged-in user. However, I'm developing an additional class, basically class SpecialUser extends IPSMember Is there a way to get the parent object, which is IPSMember to change to SpecialUser?

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  • PHP Session Class and $_SESSION Array

    - by Gianluca Bargelli
    Hello, i've implemented this custom PHP Session Class for storing sessions into a MySQL database: class Session { private $_session; public $maxTime; private $database; public function __construct(mysqli $database) { $this->database=$database; $this->maxTime['access'] = time(); $this->maxTime['gc'] = get_cfg_var('session.gc_maxlifetime'); session_set_save_handler(array($this,'_open'), array($this,'_close'), array($this,'_read'), array($this,'_write'), array($this,'_destroy'), array($this,'_clean') ); register_shutdown_function('session_write_close'); session_start();//SESSION START } public function _open() { return true; } public function _close() { $this->_clean($this->maxTime['gc']); } public function _read($id) { $getData= $this->database->prepare("SELECT data FROM Sessions AS Session WHERE Session.id = ?"); $getData->bind_param('s',$id); $getData->execute(); $allData= $getData->fetch(); $totalData = count($allData); $hasData=(bool) $totalData >=1; return $hasData ? $allData['data'] : ''; } public function _write($id, $data) { $getData = $this->database->prepare("REPLACE INTO Sessions VALUES (?, ?, ?)"); $getData->bind_param('sss', $id, $this->maxTime['access'], $data); return $getData->execute(); } public function _destroy($id) { $getData=$this->database->prepare("DELETE FROM Sessions WHERE id = ?"); $getData->bind_param('S', $id); return $getData->execute(); } public function _clean($max) { $old=($this->maxTime['access'] - $max); $getData = $this->database->prepare("DELETE FROM Sessions WHERE access < ?"); $getData->bind_param('s', $old); return $getData->execute(); } } It works well but i don't really know how to properly access the $_SESSION array: For example: $db=new DBClass();//This is a custom database class $session=new Session($db->getConnection()); if (isset($_SESSION['user'])) { echo($_SESSION['user']);//THIS IS NEVER EXECUTED! } else { $_SESSION['user']="test"; Echo("Session created!"); } At every page refresh it seems that $_SESSION['user'] is somehow "resetted", what methods can i apply to prevent such behaviour?

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  • MustOverride Shared Methods in .Net

    - by Ben
    Hi I have a few class's that inherit from a base class. I want to enforce that all of these Class's implement a shared method foo(). I am not able to create the following on the base class Public MustOvveride Shared Sub foo() as this is not allowed. I also cant create an Interface that defines a Shared Sub Foo() and implement that in my derrived class's, as this also is not allowed. Does anyone know how i should implement this? p.s i realise my example is in VB and i have also tagged C#, the same problem applies to both languages and presumably the same fix would apply.

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  • Why is there no parameter contra-variance for overriding?

    - by Oak
    C++ and Java support return-type covariance when overriding methods. Neither, however, support contra-variance in parameter types - instead, it translates to overloading (Java) or hiding (C++). Why is that? It seems to me that there is no harm in allowing that. I can find one reason for it in Java - since it has the "choose-the-most-specific-version" mechanism for overloading anyway - but can't think of any reason for C++. Example (Java): class A { public void f(String s) {...} } class B extends A { public void f(Object o) {...} // Why doesn't this override A.f? }

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