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  • Loose Coupling of Components

    - by David
    I have created a class library (assembly) that provides messaging, email and sms. This class library defines an interface IMessenger which the classes EmailMessage and SmsMessage both implement. I see this is a general library that would be part of my infrastructure layer and would / can be used across any development. Now, in my application layer I have a class that requires to use a messaging component, I obviously want to use the messaging library that I have created. Additionally, I will be using an IoC container (Spring.net) to allow me to inject my implementation i.e. either email or sms. Therefore, I want to program against an interface in my application layer class, do I then need to reference my message class library from my application layer class? Is this tightly coupling my application layer class to my message class library? Should I be defining the interface - IMessenger in a seperate library? Or should I be doing something else?

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  • My first c# app and first null object exception

    - by Fresheyeball
    Total noob here. This is my first c# attempt, its a console application that simulates a drinking game called 'Left Right Center'. In the console I receive the following: CONSOLE Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object at LeftRightCenter.MainClass.Main (System.String[] args) [0x00038] in /Users/apple/Projects/LearningC/LearningC/Main.cs:80 [ERROR] FATAL UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object at LeftRightCenter.MainClass.Main (System.String[] args) [0x00038] in /Users/apple/Projects/LearningC/LearningC/Main.cs:80 C# using System; namespace LeftRightCenter { class Player { //fields private int _quarters = 4; public int Quarters { get{ return _quarters; } set{ _quarters += value; } } public Player (string name) { } } class Dice { Random random = new Random(); public int Roll () { random = new Random (); int diceSide; diceSide = random.Next (0, 6); diceSide = (diceSide > 2) ? 3 : diceSide; return diceSide; } } class MainClass { static int activePlayer = 0; static int theCup = 0; static Player[] thePlayers = { new Player ("Jessica"), new Player ("Isaac"), new Player ("Ed"), new Player ("Bella"), new Player ("Elisa"), new Player ("Fake RedHead"), new Player ("Linda"), new Player ("MJ"), new Player ("Irene"), new Player("Devin") }; static Dice[] theDice = new Dice[2]; private static void MoveQuarter (int direction) { int numberOfPlayers = thePlayers.Length - 1; switch (direction) { case 0: thePlayers [activePlayer].Quarters = -1; theCup++; break; case 1: thePlayers [activePlayer].Quarters = -1; int leftPlayer = (activePlayer == 0) ? numberOfPlayers : activePlayer - 1; thePlayers [leftPlayer].Quarters = +1; break; case 2: thePlayers [activePlayer].Quarters = -1; int rightPlayer = (activePlayer == numberOfPlayers) ? 0 : activePlayer + 1; thePlayers [rightPlayer].Quarters = +1; break; } } public static void Main (string[] args) { int cupEndPoint = thePlayers.Length * 4 - 1; while (theCup < cupEndPoint) { foreach (Dice rattle in theDice) { if (thePlayers [activePlayer].Quarters > 0) { MoveQuarter (rattle.Roll ()); // this line seems to be the problem } } Console.WriteLine ("{0} Quarters In the Cup", theCup); } } } } I have no idea what the problem is or why, and my googling have proven more use confusing than helpful.

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  • Auto-implemented getters and setters vs. public fields

    - by tclem
    I see a lot of example code for C# classes that does this: public class Point { public int x { get; set; } public int y { get; set; } } Or, in older code, the same with an explicit private backing value and without the new auto-implemented properties: public class Point { private int _x; private int _y; public int x { get { return _x; } set { _x = value; } } public int y { get { return _y; } set { _y = value; } } } My question is why. Is there any functional difference between doing the above and just making these members public fields, like below? public class Point { public int x; public int y; } To be clear, I understand the value of getters and setters when you need to do some translation of the underlying data. But in cases where you're just passing the values through, it seems needlessly verbose.

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  • operator overloading

    - by cpp_Beginner
    Hi, Could anybody tell me the difference between operator overloading using the friend keyword and as a member function inside a class? also what is the difference incase of any unary operator overloading i.e., as a friend and as a member function

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  • wrapping aspx user controls commands in a transaction

    - by Hans Gruber
    I'm working on heavily dynamic and configurable CMS system. Therefore, many pages are composed of a dynamically loaded set of user controls. To enable loose coupling between containers (pages) and children (user controls), all user controls are responsible for their own persistence. Each User Control is wired up to its data/service layer dependencies via IoC. They also implement an IPersistable interface, which allows the container .aspx page to issue a Save command to its children without knowledge of the number or exact nature of these user controls. Note: what follows is only pseudo-code: public class MyUserControl : IPersistable, IValidatable { public void Save() { throw new NotImplementedException(); } public bool IsValid() { throw new NotImplementedException(); } } public partial class MyPage { public void btnSave_Click(object sender, EventArgs e) { foreach (IValidatable control in Controls) { if (!control.IsValid) { throw new Exception("error"); } } foreach (IPersistable control in Controls) { if (!control.Save) { throw new Exception("error"); } } } } I'm thinking of using declarative transactions from the System.EnterpriseService namespace to wrap the btnSave_Click in a transaction in case of an exception, but I'm not sure how this might be achieved or any pitfalls to such an approach.

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  • Turning PHP page calling Zend functions procedurally into Zend Framework MVC-help!

    - by Joel
    Hi guys, I posted much of this question, but if didn't include all the Zend stuff because I thought it'd be overkill, but now I'm thinking it's not easy to figure out an OO way of doing this without that code... So with that said, please forgive the verbose code. I'm learning how to use MVC and OO in general, and I have a website that is all in PHP but most of the pages are basic static pages. I have already converted them all to views in Zend Framework, and have the Controller and layout set. All is good there. The one remaining page I have is the main reason I did this...it in fact uses Zend library (for gData connection and pulling info from a Google Calendar and displaying it on the page. I don't know enough about this to know where to begin to refactor the code to fit in the Zend Framework MVC model. Any help would be greatly appreciated!! .phtml view page: <div id="dhtmltooltip" align="left"></div> <script src="../js/tooltip.js" type="text/javascript"> </script> <div id="container"> <div id="conten"> <a name="C4"></a> <?php function get_desc_second_part(&$value) { list(,$val_b) = explode('==',$value); $value = trim($val_b); } function filterEventDetails($contentText) { $data = array(); foreach($contentText as $row) { if(strstr($row, 'When: ')) { ##cleaning "when" string to get date in the format "May 28, 2009"## $data['duration'] = str_replace('When: ','',$row); list($when, ) = explode(' to ',$data['duration']); $data['when'] = substr($when,4); if(strlen($data['when'])>13) $data['when'] = trim(str_replace(strrchr($data['when'], ' '),'',$data['when'])); $data['duration'] = substr($data['duration'], 0, strlen($data['duration'])-4); //trimming time zone identifier (UTC etc.) } if(strstr($row, 'Where: ')) { $data['where'] = str_replace('Where: ','',$row); //pr($row); //$where = strstr($row, 'Where: '); //pr($where); } if(strstr($row, 'Event Description: ')) { $event_desc = str_replace('Event Description: ','',$row); //$event_desc = strstr($row, 'Event Description: '); ## Filtering event description and extracting venue, ticket urls etc from it. //$event_desc = str_replace('Event Description: ','',$contentText[3]); $event_desc_array = explode('|',$event_desc); array_walk($event_desc_array,'get_desc_second_part'); //pr($event_desc_array); $data['venue_url'] = $event_desc_array[0]; $data['details'] = $event_desc_array[1]; $data['tickets_url'] = $event_desc_array[2]; $data['tickets_button'] = $event_desc_array[3]; $data['facebook_url'] = $event_desc_array[4]; $data['facebook_icon'] = $event_desc_array[5]; } } return $data; } // load library require_once 'Zend/Loader.php'; Zend_Loader::loadClass('Zend_Gdata'); Zend_Loader::loadClass('Zend_Gdata_ClientLogin'); Zend_Loader::loadClass('Zend_Gdata_Calendar'); Zend_Loader::loadClass('Zend_Http_Client'); // create authenticated HTTP client for Calendar service $gcal = Zend_Gdata_Calendar::AUTH_SERVICE_NAME; $user = "[email protected]"; $pass = "xxxxxxxx"; $client = Zend_Gdata_ClientLogin::getHttpClient($user, $pass, $gcal); $gcal = new Zend_Gdata_Calendar($client); $query = $gcal->newEventQuery(); $query->setUser('[email protected]'); $secondary=true; $query->setVisibility('private'); $query->setProjection('basic'); $query->setOrderby('starttime'); $query->setSortOrder('ascending'); //$query->setFutureevents('true'); $startDate=date('Y-m-d h:i:s'); $endDate="2015-12-31"; $query->setStartMin($startDate); $query->setStartMax($endDate); $query->setMaxResults(30); try { $feed = $gcal->getCalendarEventFeed($query); } catch (Zend_Gdata_App_Exception $e) { echo "Error: " . $e->getResponse(); } ?> <h1><?php echo $feed->title; ?></h1> <?php echo $feed->totalResults; ?> event(s) found. <table width="90%" border="3" align="center"> <tr> <td width="20%" align="center" valign="middle"><b>;DATE</b></td> <td width="25%" align="center" valign="middle"><b>VENUE</b></td> <td width="20%" align="center" valign="middle"><b>CITY</b></td> <td width="20%" align="center" valign="middle"><b>DETAILS</b></td> <td width="15%" align="center" valign="middle"><b>LINKS</b></td> </tr> <?php if((int)$feed->totalResults>0) { //checking if at least one event is there in this date range foreach ($feed as $event) { //iterating through all events //pr($event);die; $contentText = stripslashes($event->content->text); //striping any escape character $contentText = preg_replace('/\<br \/\>[\n\t\s]{1,}\<br \/\>/','<br />',stripslashes($event->content->text)); //replacing multiple breaks with a single break //die(); $contentText = explode('<br />',$contentText); //splitting data by break tag $eventData = filterEventDetails($contentText); $when = $eventData['when']; $where = $eventData['where']; $duration = $eventData['duration']; $venue_url = $eventData['venue_url']; $details = $eventData['details']; $tickets_url = $eventData['tickets_url']; $tickets_button = $eventData['tickets_button']; $facebook_url = $eventData['facebook_url']; $facebook_icon = $eventData['facebook_icon']; $title = stripslashes($event->title); echo '<tr>'; echo '<td width="20%" align="center" valign="middle" nowrap="nowrap">'; echo $when; echo '</td>'; echo '<td width="20%" align="center" valign="middle">'; if($venue_url!='') { echo '<a href="'.$venue_url.'" target="_blank">'.$title.'</a>'; } else { echo $title; } echo '</td>'; echo '<td width="20%" align="center" valign="middle">'; echo $where; echo '</td>'; echo '<td width="20%" align="center" valign="middle">'; $details = str_replace("\n","<br>",htmlentities($details)); $duration = str_replace("\n","<br>",$duration); $detailed_description = "<b>When</b>: <br>".$duration."<br><br>"; $detailed_description .= "<b>Description</b>: <br>".$details; echo '<a href="javascript:void(0);" onmouseover="ddrivetip(\''.$detailed_description.'\')" onmouseout="hideddrivetip()" onclick="return false">View Details</a>'; echo '</td>'; echo '<td width="20%" valign="middle">'; if(trim($tickets_url) !='' && trim($tickets_button)!='') { echo '<a href="'.$tickets_url.'" target="_blank"><img src="'.$tickets_button.'" border="0" ></a>'; } if(trim($facebook_url) !='' && trim($facebook_icon)!='') { echo '<a href="'.$facebook_url.'" target="_blank"><img src="'.$facebook_icon.'" border="0" ></a>'; } else { echo '......'; } echo '</td>'; echo '</tr>'; } } else { //else show 'no event found' message echo '<tr>'; echo '<td width="100%" align="center" valign="middle" colspan="5">'; echo "No event found"; echo '</td>'; } ?> </table> <h3><a href="#pastevents">Scroll down for a list of past shows.</a></h3> <br /> <a name="pastevents"></a> <ul class="pastShows"> <?php $startDate='2005-01-01'; $endDate=date('Y-m-d'); /*$gcal = Zend_Gdata_Calendar::AUTH_SERVICE_NAME; $user = "[email protected]"; $pass = "silverroof10"; $client = Zend_Gdata_ClientLogin::getHttpClient($user, $pass, $gcal); $gcal = new Zend_Gdata_Calendar($client); $query = $gcal->newEventQuery(); $query->setUser('[email protected]'); $query->setVisibility('private'); $query->setProjection('basic');*/ $query->setOrderby('starttime'); $query->setSortOrder('descending'); $query->setFutureevents('false'); $query->setStartMin($startDate); $query->setStartMax($endDate); $query->setMaxResults(1000); try { $feed = $gcal->getCalendarEventFeed($query); } catch (Zend_Gdata_App_Exception $e) { echo "Error: " . $e->getResponse(); } if((int)$feed->totalResults>0) { //checking if at least one event is there in this date range foreach ($feed as $event) { //iterating through all events $contentText = stripslashes($event->content->text); //striping any escape character $contentText = preg_replace('/\<br \/\>[\n\t\s]{1,}\<br \/\>/','<br />',stripslashes($event->content->text)); //replacing multiple breaks with a single break $contentText = explode('<br />',$contentText); //splitting data by break tag $eventData = filterEventDetails($contentText); $when = $eventData['when']; $where = $eventData['where']; $duration = $eventData['duration']; $title = stripslashes($event->title); echo '<li class="pastShows">' . $when . " - " . $title . ", " . $where . '</li>'; } } ?> </div> </div>

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  • Placement of a call to the parent method

    - by Alejandro
    I have a class that has a method. That class has a child class that overrides that method. The child's method has to call the parent's method. In all OO that I've seen or written calls to the parent's version of the same method were on the first line of the method. On a project that I am working on circumstances call for placing that method call at the end of a method. Should I be worried? Is that a code smell? Is this code inherently bad? class Parent { function work() { // stuff } } class Child { function work() { // do thing 1 // do thing 2 parent::work(); // is this a bad practice? // should I call the parent's work() method before // I do anything in this method? } }

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  • In PHP, is it possible to create an instance of an class without calling class's constructor ?

    - by Rachel
    By any means, is it possible to create an instance of an php class without calling its constructor ? I have Class A and while creating an instance of it am passing file and in constructor of Class A am opening the file. Now in Class A, there is function which I need to call but am not required to pass file and so there is not need to use constructor functionality of opening file as am not passing file. So my question is, Is it possible by any means to create an instance of an PHP class without calling its constructor ?

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  • Properly design a code editor application

    - by Hemaulo
    I'm working on personal project which is basically a code editor. Imagine standard File menu with menu items New, Open, Save, Save As, Save All, Close, Close All. I'm stuck with proper design. Currently I have: A Document class which represents a document - code editing control, respective tab in tab bar and various properties such as Caption, Filename, IsModified etc. A Documents class which represents all open documents. Contains methods like New, Open(FileName), ... The problem is that I can't figure out which class / menu command is responsible for which tasks. For example, with File-New menu command is simple - call Documents.New and that's it. But what for File-Open? The Documents.Open method expects filename as a parameter. So before calling this method I need to open an file selection dialog, let user select files and for each file call Documents.Open(FileName). Where is best place for this supporting code, in menu command, rewrite Documents.Open and put it there? The same with Save actions. Which is responsible for saving? Is it Documents class which uses Document.Editor.SaveToFile(FileName) or better create Save method in Document class? Somewhere in the middle also need to ask user if he wants to save current document... I'm stuck. Any ideas? Edited: The programming language is Delphi.

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  • What problems do you find with this view on domain-driven design?

    - by Bozho
    I just wrote a long (and messy) blogpost about my view on domain-driven design at present day, with frameworks like spring and hibernate massively in use. I'd ask you to spot any problems with my views on the matter - why this won't work, why it isn't giving the benefits of DDD, why it is not a good idea in general. The blogpost is here (I don't think I need to copy-paste it on SO - if you think I should, tell me). I know the question is subjective, but it is aimed at gathering the most predominant opinions. (I'm tagging Java, since the frameworks discussed are Java frameworks)

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  • How to make some functions of a class as private for third level of inheritance.

    - by Shantanu Gupta
    I have created a class say A which has some functions defined as protected. Now Class B inherits A and class C inherits B. Class A has private default constructor and protected parameterized constructor. I want Class B to be able to access all the protected functions defined in Class A but class C can have access on some of the functions only not all the functions and class C is inheriting class B. How can I restrict access to some of the functions of Class A from Class C ? Class A { private A(){} protected A(int ){} protected calc(){} protected allow(){} } Class B : A {} // calc() and allow() should be accessible here CLass C:B { // calc() should not be accessible here but allow() should be accessible here. }

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  • Lightweight PHP library alternative to common MVC frameworks

    - by artarad
    Hi hi, I'm looking for a easy to learn php library to use for my coming web app project. I've recently finished a web app with fully handwritten raw php code and it's absolutely hard to be done again for another project. even though I have the recent project code snippets to be used again, but due to their non-structural arrangement (not object oriented), i have no passion to use 'em again. I have no experience with common frameworks like ZF, CakePhp, CodeIgniter, so I think to get my hands on a multipurpose OO library for my web app and the framework learning will be the next step! any suggestion? UPDATE: Many thanks guys, I have not enough time to get through the depth of every lib or framework you have kindly introduced. Since I'm going one step further I'm going to use ZF as famous framework which could provide me more job opportunities perhaps. thankssss :)

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  • GUI system architecture?

    - by topright
    I'm designing GUI (graphical user interface) system for a game engine (C++). Idea is to create a heirarchy of GUI controllers like Focusable, Hoverable, Dragable etc. Every GUI component can attach multiple controllers, they modify component's behaviour. I think it gives flexible system and protects from code duplication. Different instances of the same GUI class can have different complex behaviours (may be, even change it dynamically), so this approach looks practical. The other choice is to add focused, hovered, dragged etc. flags in the base GUI component class. It looks like overhead and not that flexible. Another solution is to use Decorator pattern and wrap objects with FocusDecorator, HoverDecorator etc. Maintaining such system looks a bit harder. Question: What are pitfalls in my solution? May be you have seen a better approaches in GUI systems? What are the best ways of implementing such flexible complex system?

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  • Most efficient way to update attribute of one instance

    - by Begbie00
    Hi all - I'm creating an arbitrary number of instances (using for loops and ranges). At some event in the future, I need to change an attribute for only one of the instances. What's the best way to do this? Right now, I'm doing the following: 1) Manage the instances in a list. 2) Iterate through the list to find a key value. 3) Once I find the right object within the list (i.e. key value = value I'm looking for), change whatever attribute I need to change. for Instance within ListofInstances: if Instance.KeyValue == SearchValue: Instance.AttributeToChange = 10 This feels really inefficient: I'm basically iterating over the entire list of instances, even through I only need to change an attribute in one of them. Should I be storing the Instance references in a structure more suitable for random access (e.g. dictionary with KeyValue as the dictionary key?) Is a dictionary any more efficient in this case? Should I be using something else? Thanks, Mike

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  • Workaround for abstract attributes in Java

    - by deamon
    In Scala I would write an abstract class with an abstract attribute path: abstract class Base { val path: String } class Sub extends Base { override val path = "/demo/" } Java doesn't know abstract attributes and I wonder what would be the best way to work around this limitation. My ideas: a) constructor parameter abstract class Base { protected String path; protected Base(String path) { this.path = path; } } class Sub extends Base { public Sub() { super("/demo/"); } } b) abstract method abstract class Base { // could be an interface too abstract String getPath(); } class Sub extends Base { public String getPath() { return "/demo/"; } } Which one do you like better? Other ideas? I tend to use the constructor since the path value should not be computed at runtime.

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  • Modelling multiple simultaneous states

    - by James P.
    How can you go about modelling an object that can have multiple simultaneous states? For example, you could have a person that's waiting for a bus. That's one state. But they could also be reading a newspaper while waiting for the bus. Furthermore, they could be thinking about something while reading the newspaper. They could also be sniffing their nose because they have a cold. That's a four states in all taking place at the same time. Obviously using booleans would be tedious and unflexible. Also, a conventional state pattern would mean that states are exclusive and can't be simultaneous in nature. The only thing I can think of is a State pattern combined with a Composite. Would this do or is there a way of taking things further?

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  • How to get associated URLRequest from Event.COMPLETE fired by URLLoader

    - by matt lohkamp
    So let's say we want to load some XML - var xmlURL:String = 'content.xml'; var xmlURLRequest:URLRequest = new URLRequest(xmlURL); var xmlURLLoader:URLLoader = new URLLoader(xmlURLRequest); xmlURLLoader.addEventListener(Event.COMPLETE, function(e:Event):void{ trace('loaded',xmlURL); trace(XML(e.target.data)); }); If we need to know the source URL for that particular XML doc, we've got that variable to tell us, right? Now let's imagine that the xmlURL variable isn't around to help us - maybe we want to load 3 XML docs, named in sequence, and we want to use throwaway variables inside of a for-loop: for(var i:uint = 3; i > 0; i--){ var xmlURLLoader:URLLoader = new URLLoader(new URLRequest('content'+i+'.xml')); xmlURLLoader.addEventListener(Event.COMPLETE, function(e:Event):void{ trace(e.target.src); // I wish this worked... trace(XML(e.target.data)); }); } Suddenly it's not so easy, right? I hate that you can't just say e.target.src or whatever - is there a good way to associate URLLoaders with the URL they loaded data from? Am I missing something? It feels unintuitive to me.

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  • strategy for observer pattern?

    - by fayer
    I want to use observer pattern for a logging system. We have got logObservers and logObservables. The class that will have to log something will implement iLogObservable and include these methods: private $logObservers = array(); public function addLogObserver($logObserver) { $this->logObservers[] = $logObserver; } public function removeLogObserver($logObserver) { $this->logObservers[] = $logObserver; } public function write($type, $message) { foreach($this->logObservers as $logObserver) { $logObserver->log($level, $message); ; } } Then I noticed, that a lot of classes that will use logging will have these methods and I have to copy paste. So isn't it better to have these methods in a class I call LogObservable or just Log and then use strategy (instantiate this class inside all classes that will have to log). When I change the methods in Log, all logObservables will be affected. However, I have not seen anyone use observer pattern with strategy pattern yet, but it seems to be very efficient and remove the duplications. What do you think?

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  • A Question on Encapsulation.

    - by Bragaadeesh
    Hi, I know that encapsulation is binding the members and its behavior in one single entity. And it has made me think that the members have to be private. Does this mean if a class having public members is not following 100% Encapsulation rule? Thanks

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  • PHP 'instanceof' failing with class constant

    - by Nathan Loding
    I'm working on a framework that I'm trying to type as strongly as I possibly can. (I'm working within PHP and taking some of the ideas that I like from C# and trying to utilize them within this framework.) I'm creating a Collection class that is a collection of domain entities/objects. It's kinda modeled after the List<T> object in .Net. I've run into an obstacle that is preventing me from typing this class. If I have a UserCollection, it should only allow User objects into it. If I have a PostCollection, it should only allow Post objects. All Collections in this framework need to have certain basic functions, such as add, remove, iterate. I created an interface, but found that I couldn't do the following: interface ICollection { public function add($obj) } class PostCollection implements ICollection { public function add(Post $obj) {} } This broke it's compliance with the interface. But I can't have the interface strongly typed because then all Collections are of the same type. So I attempted the following: interface ICollection { public function add($obj) } abstract class Collection implements ICollection { const type = 'null'; } class PostCollection { const type = 'Post'; public function add($obj) { if(!($obj instanceof self::type)) { throw new UhOhException(); } } } When I attempt to run this code, I get syntax error, unexpected T_STRING, expecting T_VARIABLE or '$' on the instanceof statement. A little research into the issue and it looks like the root of the cause is that $obj instanceof self is valid to test against the class. It appears that PHP doesn't process the entire self::type constant statement in the expression. Adding parentheses around the self::type variable threw an error regarding an unexpected '('. An obvious workaround is to not make the type variable a constant. The expression $obj instanceof $this->type works just fine (if $type is declared as a variable, of course). I'm hoping that there's a way to avoid that, as I'd like to define the value as a constant to avoid any possible change in the variable later. Any thoughts on how I can achieve this, or have I take PHP to it's limit in this regard? Is there a way of "escaping" or encapsulating self::this so that PHP won't die when processing it?

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  • Calling a subclass method from a superclass

    - by Shaun
    Preface: This is in the context of a Rails application. The question, however, is specific to Ruby. Let's say I have a Media object. class Media < ActiveRecord::Base end I've extended it in a few subclasses: class Image < Media def show # logic end end class Video < Media def show # logic end end From within the Media class, I want to call the implementation of show from the proper subclass. So, from Media, if self is a Video, then it would call Video's show method. If self is instead an Image, it would call Image's show method. Coming from a Java background, the first thing that popped into my head was 'create an abstract method in the superclass'. However, I've read in several places (including Stack Overflow) that abstract methods aren't the best way to deal with this in Ruby. With that in mind, I started researching typecasting and discovered that this is also a relic of Java thinking that I need to banish from my mind when dealing with Ruby. Defeated, I started coding something that looked like this: def superclass_method # logic this_media = self.type.constantize.find(self.id) this_media.show end I've been coding in Ruby/Rails for a while now, but since this was my first time trying out this behavior and existing resources didn't answer my question directly, I wanted to get feedback from more-seasoned developers on how to accomplish my task. So, how can I call a subclass's implementation of a method from the superclass in Rails? Is there a better way than what I ended up (almost) implementing?

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  • Object-oriented GUI development in python

    - by ptabatt
    Hey guys, new programmer here. I have an assignment for class and I'm stuck... What I need to do is a create a GUI that gives someone a basic arithmetic problem in one box, asks the person to answer it, evaluates it, and tells you if you're right or wrong... Basically, what I have is this: [code] class Lesson(Frame): def init (self, parent=None): Frame.init(self, parent) self.pack() Lesson.make_widgets(self) def make_widgets(self): Label(self, text="").pack(side=TOP) ent = Entry(self) self.a = randrange(1,10) self.b = randrange(1,10) self.expr = choice(["+","-"]) ent.insert(END, str(self.a) + str(self.expr) + str(self.a)) [/code] I've broken this down into many little steps and basically, what I'm trying to do right now is insert a default random expression into the first entry widget. When I run this code, I just get a blank Label. Why is that? How can I put a something like "7+7" into the box? If you absolutely need background to the problem, it's question #3 on this link. http://reed.cs.depaul.edu/lperkovic/csc242/homeworks/Homework8.html -Thanks for all help in advance.

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