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  • Interesting OOPS puzzle

    - by user3714387
    Recently, faced the below question from one of the interviewer. Initially thought that the question was wrong, but the interviewer mentioned there is solution for this. Quite interesting. Can anyone shed light please ? Program as below. public class BaseHome { public static void main() { Console.WriteLine("A"); } } Required output : B A C Condition : Should not make any change in the Main function. Should not create any additional class. Please advice if this can be done with the condition met.

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  • how can I get around no arrays as class constants in php?

    - by user151841
    I have a class with a static method. There is an array to check that a string argument passed is a member of a set. But, with the static method, I can't reference the class property in an uninstantiated class, nor can I have an array as a class constant. I suppose I could hard code the array in the static method, but then if I need to change it, I'd have to remember to change it in two places. I'd like to avoid this.

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  • Multiple Inheritance Debates II: according to Stroustrup

    - by asksuperuser
    I know very well about the traditional arguments about why Interface Inheritance is prefered to multiple inheritance, there has been already a post here : http://stackoverflow.com/questions/191691/should-c-include-multiple-inheritance But according to Stroustrup the real reason why Microsoft and Sun decided to get rid off multiple inheritance is that they have vested interest to do so: instead of putting features in the languages, they put in frameworks so that people then become tied to their platform instead of people having the same capability at a language standard level. What do you think ? Why Sun and Microsoft consider developers too immature to just make the choice themselves ?

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  • Constructors + Dependency Injection

    - by Sunny
    If I am writing up a class with more than 1 constructor parameter like: class A{ public A(Dependency1 d1, Dependency2 d2, ...){} } I usually create a "argument holder"-type of class like: class AArgs{ public Dependency1 d1 { get; private set; } public Dependency2 d2 { get; private set; } ... } and then: class A{ public A(AArgs args){} } Typically, using a DI-container I can configure the constructor for dependencies & resolve them & so there is minimum impact when the constructors need to change. Is this considered an anti-pattern and/or any arguments against doing this?

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  • Is it possible to cancel function override in parent class and use function from top level parent

    - by Anatoliy Gusarov
    class TopParent { protected function foo() { $this->bar(); } private function bar() { echo 'Bar'; } } class MidParent extends TopParent { protected function foo() { $this->midMethod(); parent::foo(); } public function midMethod() { echo 'Mid'; } public function generalMethod() { echo 'General'; } } Now the question is if I have a class, that extends MidParent because I need to call class Target extends MidParent { //How to override this method to return TopParent::foo(); ? protected function foo() { } } So I need to do this: $mid = new MidParent(); $mid->foo(); // MidBar $taget = new Target(); $target->generalMethod(); // General $target->foo(); // Bar UPDATE Top parent is ActiveRecord class, mid is my model object. I want to use model in yii ConsoleApplication. I use 'user' module in this model, and console app doesn't support this module. So I need to override method afterFind, where user module is called. So the Target class is the class that overrides some methods from model which uses some modules that console application doesn't support.

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  • Python - Is it possible to get the name of the chained function?

    - by user1326876
    I'm working on a class that basically allows for method chaining, for setting some attrbutes for different dictionaries stored. The syntax is as follows: d = Test() d.connect().setAttrbutes(Message=Blah, Circle=True, Key=True) But there can also be other instances, so, for example: d = Test() d.initialise().setAttrbutes(Message=Blah) Now I believe that I can overwrite the "setattrbutes" function; I just don't want to create a function for each of the dictionary. Instead I want to capture the name of the previous chained function. So in the example above I would then be given "connect" and "initialise" so I know which dictionary to store these inside. I hope this makes sense. Any ideas would be greatly appreciated :)

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  • Can you explain this generics behavior and if I have a workaround?

    - by insta
    Sample program below: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace GenericsTest { class Program { static void Main(string[] args) { IRetrievable<int, User> repo = new FakeRepository(); Console.WriteLine(repo.Retrieve(35)); } } class User { public int Id { get; set; } public string Name { get; set; } } class FakeRepository : BaseRepository<User>, ICreatable<User>, IDeletable<User>, IRetrievable<int, User> { // why do I have to implement this here, instead of letting the // TKey generics implementation in the baseclass handle it? //public User Retrieve(int input) //{ // throw new NotImplementedException(); //} } class BaseRepository<TPoco> where TPoco : class,new() { public virtual TPoco Create() { return new TPoco(); } public virtual bool Delete(TPoco item) { return true; } public virtual TPoco Retrieve<TKey>(TKey input) { return null; } } interface ICreatable<TPoco> { TPoco Create(); } interface IDeletable<TPoco> { bool Delete(TPoco item); } interface IRetrievable<TKey, TPoco> { TPoco Retrieve(TKey input); } } This sample program represents the interfaces my actual program uses, and demonstrates the problem I'm having (commented out in FakeRepository). I would like for this method call to be generically handled by the base class (which in my real example is able to handle 95% of the cases given to it), allowing for overrides in the child classes by specifying the type of TKey explicitly. It doesn't seem to matter what parameter constraints I use for the IRetrievable, I can never get the method call to fall through to the base class. Also, if anyone can see an alternate way to implement this kind of behavior and get the result I'm ultimately looking for, I would be very interested to see it. Thoughts?

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  • Updating the Jpanel of a class

    - by ivor
    Hi, After some advice on using jpanel - I'm new to java and playing around with the GUI elements. Bascially what I'm curious about is if I can set up a Jpanel in one class, then somehow add labels etc to the that container, but from another class. Is this possible ? or do i have to set the entire GUI up in one class, but then I guess I would have the same issue, if I wanted to update those fields I had set up in the main class from another class? Apologies I don't really have any code that's usefull to demostrate here - I'm just trying to get the idea going, working out if its possible before I go ahead. And I'm not even sure if this is possible. Any advice would be greatly appreciated. Thanks

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  • how to make functions global?

    - by fayer
    i'm trying to follow DRY and i've got some functions i have to reuse. i put them all as static functions in a class and want to use them in another class. what is the best way to make them available to a class. cause i can't extend the class, its already extended. should/could i use composition? what is best practice? thanks!

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  • What pattern is this? php

    - by user151841
    I have several classes that are basically interfaces to database rows. Since the class assumes that a row already exists ( __construct expects a field value ), there is a public static function that allows creation of the row and returns an instance of the class. Here's an example ( without the actual database inserts ): class selfStarter { public $type; public function __construct( $type ) { $this->type = $type; } public static function create( $type ) { if ( ! empty($type) ) { $starter = & new selfStarter($type); return $starter; } } } $obj1 = selfStarter::create( "apple" ); $obj2 = & new selfStarter( "banana" ); What is this pattern called?

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  • How to structure a bigger/complicated project?

    - by Per
    Hello, I'm creating this (big?) project in high school where I'm programming the game Shithead (card game) (so that two people can play against eachother). I'll use mostly PHP, MySQL, JavaScript and Ajax. But I have never made a project like this before. I have only made like CMS-systems and so on. Do you guys have any tips on how I should structure this project? I'm also not so used to Object-oriented programming, but I guess I should consider this. Should I, for example, make a class for the cards? I'm very thankful for any tips or good links!

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  • [[alloc] init] as a factory method

    - by iter
    I want to initialize an instance of one of the subclasses of a superclass depending on the arguments to init: [[Vehicle alloc] initWithItinerary: shortWay]; // returns a bicycle [[Vehicle alloc] initWithItinerary: longWay]; // returns a car I can't find examples of code like this. I wonder if this is not idiomatic in Objective C, or I simply am not looking in the right places.

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  • AS3 Passing data between objects/classes

    - by 1337holiday
    So i a building a categorized menu of different foods. I have a class for "categories" (buttons) which essentially will return a string "salads", "drinks", etc. I now have another class "menuItems" for items within categories and this handles sizes such as "small", "med", "large", etc. My problem now is that when i return "salads", i want to invoke an array which contains all the elements of salads, send it to menuItems which will populate the menu. So far i have both the category objects and the menu object setup. I just cant seem to be able to send the data that the category object is returning and pass it to the menu object. Both of which are added to the stage as shown below: If there was a way that i could say add all these classes to one class so that they can talk to each other that would be great but i dont know how to do this. Been stuck for hours, please any help is greatly appreciated.

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  • Refactoring huge if ( ... instanceof ...)

    - by Chris
    I'm currently trying to refactor a part of a project that looks like this: Many classes B extends A; C extends A; D extends C; E extends B; F extends A; ... And somewhere in the code: if (x instanceof B){ B n = (B) x; ... }else if (x instanceof C){ C n = (C) x; ... }else if (x instanceof D){ D n = (D) x; ... }else if (x instanceof E){ E n = (E) x; ... }else if (x instanceof G){ G n = (G) x; ... }... Above if-construct currently sits in a function with a CC of 19. Now my question is: Can I split this if-construct up in mutliple functions and let Java's OO do the magic? Or are there any catches I have to look out for? My idea: private void oopMagic(C obj){ ... Do the stuff from the if(x instanceof C) here} private void oopMagic(D obj){ ... Do the stuff from the if(x instanceof D) here} private void oopMagic(E obj){ ... Do the stuff from the if(x instanceof E) here} .... and instead of the huge if: oopMagic(x);

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  • PHP inheriting/extending a particular instance of an Object

    - by delta9
    Is there any way to force PHP to extend an existing/particular (and for that matter, already instantiated) instance of an object? This imaginary code should explain what I am wondering: class Base { public $var; function __construct($var){ $this->var = $name; } } class Extender extends Base { function __construct($parent) { parent = $parent; } } $base = new Base('yay!'); $extender = new Extender($base); echo 'Extended base var value: '.$extender->var.'<br/>'; Output (would be): Extended base var value: yay! To be clear, I am wanting to instantiate an object that extends a PARTICULAR INSTANCE of another object, one that has already been instantiated. I am aware that I can pass a reference to an object to another object (via it's constructor function) and then add it as a property of the receiving object, I'm wondering if there is a real way to do this?

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  • Accessing a function of an instance which is in an arraylist

    - by fadeir
    I'm tring to access a function of an instance which is in an arraylist. Is there any way to do that without using the class name of the instance? import java.util.ArrayList; import java.util.List; class apple{ int price; public void myFunction(int iPrice) { price=iPrice; } } class orange{ int price; public void myFunction(int iPrice) { price=iPrice; } } public class main { public static void main(String[] args) { List list= new ArrayList(); //create 3 apple object to list list.add( new apple() ); list.add( new apple() ); list.add( new orange() ); list.get(0).myFunction(1); /* Error: The method myFunction(int) is undefined for the type Object*/ } } I know that;((apple) list.get(0)).myFunction(1); is a way but I'dont want to use any class name while calling the function.

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  • How to output multiple rows from an SQL query using the mysqli object

    - by Jonathan
    Assuming that the mysqli object is already instantiatied (and connected) with the global variable $mysql, here is the code I am trying to work with. class Listing { private $mysql; function getListingInfo($l_id = "", $category = "", $subcategory = "", $username = "", $status = "active") { $condition = "`status` = '$status'"; if (!empty($l_id)) $condition .= "AND `L_ID` = '$l_id'"; if (!empty($category)) $condition .= "AND `category` = '$category'"; if (!empty($subcategory)) $condition .= "AND `subcategory` = '$subcategory'"; if (!empty($username)) $condition .= "AND `username` = '$username'"; $result = $this->mysql->query("SELECT * FROM listing WHERE $condition") or die('Error fetching values'); $this->listing = $result->fetch_array() or die('could not create object'); foreach ($this->listing as $key => $value) : $info[$key] = stripslashes(html_entity_decode($value)); endforeach; return $info; } } there are several hundred listings in the db and when I call $result-fetch_array() it places in an array the first row in the db. however when I try to call the object, I can't seem to access more than the first row. for instance: $listing_row = new Listing; while ($listing = $listing_row-getListingInfo()) { echo $listing[0]; } this outputs an infinite loop of the same row in the db. Why does it not advance to the next row? if I move the code: $this->listing = $result->fetch_array() or die('could not create object'); foreach ($this->listing as $key => $value) : $info[$key] = stripslashes(html_entity_decode($value)); endforeach; if I move this outside the class, it works exactly as expected outputting a row at a time while looping through the while statement. Is there a way to write this so that I can keep the fetch_array() call in the class and still loop through the records?

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  • How to implement copy operator for such C++ structure?

    - by Kabumbus
    So having struct ResultStructure { ResultStructure(const ResultStructure& other) { // copy code in here ? using memcpy ? how??? } ResultStructure& operator=(const ResultStructure& other) { if (this != &other) { // copy code in here ? } return *this } int length; char* ptr; }; How to implement copy? (sorry - I am C++ nube)

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  • How to access constant defined in child class?

    - by kavoir.com
    I saw this example from php.net: <?php class MyClass { const MY_CONST = "yonder"; public function __construct() { $c = get_class( $this ); echo $c::MY_CONST; } } class ChildClass extends MyClass { const MY_CONST = "bar"; } $x = new ChildClass(); // prints 'bar' $y = new MyClass(); // prints 'yonder' ?> But $c::MY_CONST is only recognized in version 5.3.0 or later. The class I'm writing may be distributed a lot. Basically, I have defined a constant in ChildClass and one of the functions in MyClass (father class) needs to use the constant. Any idea?

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  • Class member variables, methods and their state

    - by codeMonkey
    How should class member variables be used in combination with class methods? Let's say I have a class 'C' with a member variable 'someData'. I call C.getData(), which does not return a value but instead puts data in C.someData. The class that instantiated 'C' first calls C.getData and then uses the data by accessing the member variable C.someData. I call C.getData() in the class that instantiated 'C' which is a function that returns data. I myself prefer the second way. But it also depends on the situation and it's a small difference. Is it 'bad' to have class methods that depend on the classes internal state? What are the best conventions?

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  • I'm confused about Polymorphism

    - by Vtanathip
    I'm know polymorphism rule that we can send it via parameter like this code interface Animal { void whoAmI(); } class A implements Animal{ @Override public void whoAmI() { // TODO Auto-generated method stub System.out.println("A"); } } class B implements Animal{ @Override public void whoAmI() { // TODO Auto-generated method stub System.out.println("B"); } } class RuntimePolymorphismDemo { public void WhoRU(List t){ System.out.println(t.getClass()); } public static void main(String[] args) { A a = new A(); B b = new B(); RuntimePolymorphismDemo rp = new RuntimePolymorphismDemo(); rp.WhoRU(a); rp.WhoRU(b); } } but List<Example> examples = new ArrayList<Example>(); This code,I'm don't understand why we must use List. why we can't use like this? ArrayList<Example> examples = new ArrayList<Example>(); Because when we use List we can't use method that only have in ArrayList class like trimToSize() and How I know when to use or not use?

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  • JavaScript prototype(ing) question

    - by OneNerd
    Trying to grasp Prototyping in Javascript. Trying to create my own namespace to extend the String object in JavaScript. Here is what I have so far (a snippet): var ns { alert: function() { alert (this); } } String.prototype.$ns = ns; As you can see, I am trying to place what will be a series of functions into the ns namespace. So I can execute a command like this: "hello world".$ns.alert(); But the problem is, the this doesn't seem to reference the text being sent (in this case, "hello world"). What I get is an alert box with the following: [object Object] Not having a full grasp of the object-oriented nature of JavaScript, I am at a loss, but I am guessing I am missing something simple. Does anyone know how to achieve this? Thanks -

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  • Best way to make an attribute always an array?

    - by Shadowfirebird
    I'm using my MOO project to teach myself Test Driven Design, and it's taking me interesting places. For example, I wrote a test that said an attribute on a particular object should always return an array, so -- t = Thing.new("test") p t.names #-> ["test"] t.names = nil p t.names #-> [] The code I have for this is okay, but it doesn't seem terribly ruby to me: class Thing def initialize(names) self.names = names end def names=(n) n = [] if n.nil? n = [n] unless n.instance_of?(Array) @names = n end attr_reader :names end Is there a more elegant, Ruby-ish way of doing this? (NB: if anyone wants to tell me why this is a dumb test to write, that would be interesting too...)

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