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• Question on overview of C# OOP in business WinForms application - scope of Object

  - by TimR

  I may have all this OO completely wrong, but here goes: Ok the scenario is a classic order entry. Customer places an Order which has OrderLineItems of StockItems. Order is entered by Employee. 1) Application starts and asks for login/password 2) Employee selects 'Orders' from Mainmenu form 3) Orders forms opens.... 4) Employee selects Customer 5) Employee selects Stock adds to OrderLineItems 6) Selects second StockItem; add to OrderLineItems 7) Order is committed, [stock decremented, order posted to DB, Order printed] 8) Employee is returned to MainMenu Now with Object scope: 1) Application starts and asks for login/password Is this the best place to make objEmployee, to be kept whilst in this whole Sales application? 2) Employee selects 'Orders' from Mainmenu form 3) Orders forms opens.... *Make objOrderHeader, is objEmployee able to be passed in or is it created here, or re-created here.* 4) Employee selects Customer - adds/edits Customer details if required... Make objCustomer 5) Employee selects Stock adds to OrderLineItems... *Make objStockItem and objOrderLineItem - add to objOrderLineItems_collection* 6) Selects second StockItem; add to OrderLineItems... *Make objStockItem and objOrderLineItem - add to objOrderLineItems_collection* 7) Order is committed, [stock decremented, order posted to DB, Order printed, Order Entered By = EmployeeID] Once posted to Db, all objects now redundant/garbage [except objEmployee?] 8) Employee is returned to MainMenu is objEmployee still valid as an object?

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• Do delegates defy OOP

  - by Dave Rook

  I'm trying to understand OOP so I can write better OOP code and one thing which keeps coming up is this concept of a delegate (using .NET). I could have an object, which is totally self contained (encapsulated); it knows nothing of the outside world... but then I attach a delegate to it. In my head, this is still quite well separated as the delegate only knows what to reference, but this by itself means it has to know about something else outside it's world! That a method exists within another class! Have I got myself it total muddle here, or is this a grey area, or is this actually down to interpretation (and if so, sorry as that will be off topic I'm sure). My question is, do delegates defy/muddy the OOP pattern?

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• Javascript MVC in principle

  - by Michael

  Suppose I want to implement MVC in JavaScript. I am not asking about MVC frameworks. I am asking how to build it in principle. Let's consider a search page of an e-commerce site, which works s follows: User chooses a product and its attributes and press a "search" button. Application sends the search request to the server, receives a list of products. Application displays the list in the web page. I think the Model holds a Query and list of Product objects and "publishes" such events as "query updated", "list of products updated", etc. The Model is not aware of DOM and server, or course. View holds the entire DOM tree and "subscribes" to the Model events to update the DOM. Besides, it "publishes" such events as "user chose a product", "user pressed the search button" etc. Controller does not hold any data. It "subscribes" to the View events, calls the server and updates the Model. Does it make sense?

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• OOP, Interface Design and Encapsulation

  - by Mau

  C# project, but it could be applied to any OO languages. 3 interfaces interacting: public interface IPublicData {} public /* internal */ interface IInternalDataProducer { string GetData(); } public interface IPublicWorker { IPublicData DoWork(); IInternalDataProducer GetInternalProducer(); } public class Engine { Engine(IPublicWorker worker) {} IPublicData Run() { DoSomethingWith(worker.GetInternalProducer().GetData()); return worker.DoWork(); } } Clearly Engine is parametric in the actual worker that does the job. A further source of parametrization is how we produce the 'internal data' via IInternalDataProducer. This implementation requires IInternalDataProducer to be public because it's part of the declaration of the public interface IPublicWorker. However, I'd like it to be internal since it's only used by the engine. A solution is make the IPublicWorker produce the internal data itself, but that's not very elegant since there's only a couple of ways of producing it (while there are many more worker implementations), therefore it's nice to delegate to a couple of separate concrete classes. Moreover, the IInternalDataProducer is used in more places inside the engine, so it's good for the engine to pass around the actual object. I'm looking for elegant ideas/patterns. Cheers :-)

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• PHP OOP singleton doesn't return object

  - by Misiur

  Weird trouble. I've used singleton multiple times but this particular case just doesn't want to work. Dump says that instance is null. define('ROOT', "/"); define('INC', 'includes/'); define('CLS', 'classes/'); require_once(CLS.'Core/Core.class.php'); $core = Core::getInstance(); var_dump($core->instance); $core->settings(INC.'config.php'); $core->go(); Core class class Core { static $instance; public $db; public $created = false; private function __construct() { $this->created = true; } static function getInstance() { if(!self::$instance) { self::$instance = new Core(); } else { return self::$instance; } } public function settings($path = null) { ... } public function go() { ... } } Error code Fatal error: Call to a member function settings() on a non-object in path It's possibly some stupid typo, but I don't have any errors in my editor. Thanks for the fast responses as always.

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• What should I "forget" when going to Javascript?

  - by ElGringoGrande

  I went from C=64 Basic and assembler to FORTRAN and C to C++ and Java. Professionally I started in Visual Basic for applications then to Visual Basic 4, 5, 6. After that VB.NET AND C# with some Java here and there. I have played with Ruby and Python and found both fun. During each step I never felt like I had to forget what I had learned before. I always felt like I was just learning better and/or slightly different ways of doing things but the difference was not major. The difference was like the difference between American, Australian and British English. (Maybe assembler was Latin and FORTRAN was Spanish.) But now I am using JavaScript to do real, actual work. (Before used it as a "Scripting" language pure a simple.) And I just feel like I have to forget some things to become proficient in it. It feels like some old Egyptian language. What should I forget? Is it just that code organization is different (no real classes so no one class one file)? Or is it something more basic?

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• Unable to debug an encodded javascript?

  - by miles away

  I’m having some problems debugging an encoded javacscript. This script I’m referring to given in this link over here. The encoding here is simple and it works by shifting the unicodes values to whatever Codekey was use during encoding. The code that does the decoding is given here in plain English below:- <script language="javascript"> function dF(s){ var s1=unescape(s.substr(0,s.length-1)); var t=''; for(i=0;i<s1.length;i++)t+=String.fromCharCode(s1.charCodeAt(i)-s.substr(s.length-1,1)); document.write(unescape(t)); } </script> I’m interested in knowing or understanding the values (e.g s1,t). Like for example when the value of i=0 what values would the following attributes / method would hold s1.charCodeAt(i) and s.substr(s.length-1,1) The reason I’m doing this is to understand as to how a CodeKey function really works. I don’t see anything in the code above which tells it to decode on the basis of codekey value. The only thing I can point in the encoding text is the last character which is set to 1 , 2 ,3 or 4 depending upon the codekey selected during encoding process. One can verify using the link I have given above. However, to debug, I’m using firebug addon with the script running as localhost on my wamp server. I’m able to put a breakpoint on the js using firebug but I’m unable to retrieve any of the user defined parameters or functions I mentioned above. I want to know under this context what would be best way to debug this encoded js.

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• PHP OOP: Avoid Singleton/Static Methods in Domain Model Pattern

  - by sunwukung

  I understand the importance of Dependency Injection and its role in Unit testing, which is why the following issue is giving me pause: One area where I struggle not to use the Singleton is the Identity Map/Unit of Work pattern (Which keeps tabs on Domain Object state). //Not actual code, but it should demonstrate the point class Monitor{//singleton construction omitted for brevity static $members = array();//keeps record of all objects static $dirty = array();//keeps record of all modified objects static $clean = array();//keeps record of all clean objects } class Mapper{//queries database, maps values to object fields public function find($id){ if(isset(Monitor::members[$id]){ return Monitor::members[$id]; } $values = $this->selectStmt($id); //field mapping process omitted for brevity $Object = new Object($values); Monitor::new[$id]=$Object return $Object; } $User = $UserMapper->find(1);//domain object is registered in Id Map $User->changePropertyX();//object is marked "dirty" in UoW // at this point, I can save by passing the Domain Object back to the Mapper $UserMapper->save($User);//object is marked clean in UoW //but a nicer API would be something like this $User->save(); //but if I want to do this - it has to make a call to the mapper/db somehow $User->getBlogPosts(); //or else have to generate specific collection/object graphing methods in the mapper $UserPosts = $UserMapper->getBlogPosts(); $User->setPosts($UserPosts); Any advice on how you might handle this situation? I would be loathe to pass/generate instances of the mapper/database access into the Domain Object itself to satisfy DI - At the same time, avoiding that results in lots of calls within the Domain Object to external static methods. Although I guess if I want "save" to be part of its behaviour then a facility to do so is required in its construction. Perhaps it's a problem with responsibility, the Domain Object shouldn't be burdened with saving. It's just quite a neat feature from the Active Record pattern - it would be nice to implement it in some way.

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• Problem with OOP Class Definitions

  - by oben

  Hi, this is Oben from Turkey. I work for my homework in C++ and i have some problems with multiply definitions. My graph class ; class Graph{ private: string name; //Graph name fstream* graphFile; //Graph's file protected: string opBuf; //Operations buffer int containsNode(string); //Query if a node is present Node* nodes; //Nodes in the graph int nofNodes; //Number of nodes in the graph public: static int nOfGraphs; //Number of graphs produced Graph(); //Constructors and destructor Graph(int); Graph(string); Graph(const Graph &); ~Graph(); string getGraphName(); //Get graph name bool addNode(string); //add a node to the graph bool deleteNode(string); //delete a node from the graph bool addEdge(string,string); //add an edge to the graph bool deleteEdge(string,string); //delete an edge from the graph void intersect(const Graph&); //intersect the graph with the <par> void unite(const Graph&); //intersect the graph with the <par> string toString(); //get string representation of the graph void acceptTraverse(BreadthFirst*); void acceptTraverse(DepthFirst *); }; and my traversal class; class Traversal { public: string *visitedNodes; virtual string traverse (const Graph & ); }; class BreadthFirst : public Traversal { public : BreadthFirst(); string traverse(); }; class DepthFirst : public Traversal { public : DepthFirst(); string traverse(); }; My problem is in traversal class , i need to declare Graph class at the same time , in graph class i need traversal class to declare. I have big problems with declerations :) Could you please help me ?

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• Is OOP based on any branch of mathematics?

  - by ektrules

  I know relational databases are based on set-theory, functional programming is based on lambda calculus, logic programming is based on logic (of course :)), and now that I think of it; I'm not sure if imperative and generic programming is based on any particular branch of mathematics either.

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• OOP C# Question: Making a Fruit a Pear

  - by Adam Kane

  Given that I have an instance of Fruit with some properties set, and I want to get those properties into a new Pear instance (because this particular Fruit happens to have the qualities of a pear), what's the best way to achieve this effect? For example, what we can't do is simple cast a Fruit to a Pear, because not all Fruits are Pears: public static class PearGenerator { public static Pear CreatePear () { // Make a new generic fruit. Fruit genericFruit = new Fruit(); // Upcast it to a pear. (Throws exception: Can't cast a Fruit to a Pear.) Pear pear = (Pear)genericFruit; // Return freshly grown pear. return ( pear ); } } public class Fruit { // some code } public class Pear : Fruit { public void PutInPie () { // some code } } Thanks! Update: I don't control the "new Fruit()" code. My starting point is that I've got a Fruit to work with. I need to get that Fruit into a new Pear somehow. Maybe copy all the properties one by one?

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• inheritance problem OOP extend

  - by hsmit

  If a Father is a Parent and a Parent is a Person and a Person has a Father I create the following: class Person{ Father father; } class Parent extends Person{} class Father extends Parent{} Instances: Person p1 = new Person(); Person p2 = new Person(); p1.father = p2; //father is of the type Father This doesn't work... Now try casting:: Person p1 = new Person(); Person p2 = new Person(); p1.father = (Father)p2; This doesn't work either. What does work for this case?

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• Question about OOP and objects.

  - by loddn

  I have a school assignment, a Dog Show. My assignment is to create a website where vistors can display results and Judges and Secretary can admin, crud. I have a small problem one part of the assignment. The result should be based on two protokols from different judges and after that checked by the secretary before the result is displayed for the user. I have to say i'm fairly new to programming and so i need some smart suggestions on how to design and implement this. The assignment should cover both a db and c# (.net mvc). Q1: How do i create a object (result)that depends on two other objects(protocol)? Is that even needed? Q2: How to solve this in a relational db?

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• JavaScript and callback nesting

  - by Jake King

  A lot of JavaScript libraries (notably jQuery) use chaining, which allows the reduction of this: var foo = $(".foo"); foo.stop(); foo.show(); foo.animate({ top: 0 }); to this: $(".foo").stop().show().animate({ top: 0 }); With proper formatting, I think this is quite a nice syntactic capability. However, I often see a pattern which I don't particularly like, but appears to be a necessary evil in non-blocking models. This is the ever-present nesting of callback functions: $(".foo").animate({ top: 0, }, { callback: function () { $.ajax({ url: 'ajax.php', }, { callback: function () { ... } }); } }); And it never ends. Even though I love the ease non-blocking models provide, I hate the odd nesting of function literals it forces upon the programmer. I'm interesting in writing a small JS library as an exercise, and I'd love to find a better way to do this, but I don't know how it could be done without feeling hacky. Are there any projects out there that have resolved this problem before? And if not, what are the alternatives to this ugly, meaningless code structure?

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• OOP design issue: Polymorphism

  - by Graham Phillips

  I'm trying to solve a design issue using inheritance based polymorphism and dynamic binding. I have an abstract superclass and two subclasses. The superclass contains common behaviour. SubClassA and SubClassB define some different methods: SubClassA defines a method performTransform(), but SubClassB does not. So the following example 1 var v:SuperClass; 2 var b:SubClassB = new SubClassB(); 3 v = b; 4 v.performTransform(); would cause a compile error on line 4 as performTransform() is not defined in the superclass. We can get it to compile by casting... (v as SubClassA).performTransform(); however, this will cause a runtime exception to be thrown as v is actually an instance of SubClassB, which also does not define performTransform() So we can get around that by testing the type of an object before casting it: if( typeof v == SubClassA) { (cast v to SubClassA).performTransform(); } That will ensure that we only call performTransform() on v's that are instances of SubClassA. That's a pretty inelegant solution to my eyes, but at least its safe. I have used interface based polymorphism (interface meaning a type that can't be instantiated and defines the API of classes that implement it) in the past, but that also feels clunky. For the above case, if SubClassA and SubClassB implemented ISuperClass that defined performTransform, then they would both have to implement performTransform(). If SubClassB had no real need for a performTransform() you would have to implement an empty function. There must be a design pattern out there that addresses the issue.

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• Help w/ iPad 1 performance for tile-based DOM Javascript game

  - by butr0s

  I've made a 2D tile-based game with DOM/Javascript. For each level, the map data is loaded and parsed, then lots of tiles ( elements) are drawn onto a larger "map" element. The map is inside of a container that hides overflow, so I can move the map element around by positioning it absolutely. Works a treat on desktop browsers, and my iPad 2. My problem is that performance is really bad on iPad 1. The performance hit is directly related to all the tile elements in my map, because when I remove or reduce the number of tiles drawn, performance improves. Optimizing my collision detection loop has no effect. My first thought was to batch groups of tiles into containers, then hide/show them based on proximity to the player, however this still causes a huge hiccup when the player moves and a new group of tiles is displayed (offscreen). Actually removing the out-of-sight elements from the DOM, then re-adding them as necessary is no faster. Anyone know of any tips that might speed up DOM performance here? My map is 1920 x 1920 pixels, so as far as I know should be within the WebKit texture limit on iOS 5/iPad. The map is being moved with CSS3 transforms, and I've picked all the other obvious low-hanging fruit.

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• Javascript storing data

  - by user985482

  Hi I am a beginner web developer and am trying to build the interface of a simple e-commerce site as a personal project.The site has multiple pages with checkboxes.When someone checks an element it retrives the price of the element and stores it in a variable.But when I go to the next page and click on new checkboxes products the variable automaticly resets to its original state.How can I save the value of that variable in Javascript? This is the code I've writen using sessionStorage but it still dosen't work when I move to next page the value is reseted. How can I wright this code so that i dosen't reset on each page change.All pages on my website use the same script. $(document).ready(function(){ var total = 0; $('input.check').click(function(){ if($(this).attr('checked')){ var check = parseInt($(this).parent().children('span').text().substr(1 , 3)); total+=check; sessionStorage.var_name=0 + total; alert(sessionStorage.var_name); }else{ var uncheck = parseInt($(this).parent().children('span').text().substr(1 , 3)); total-=uncheck; } })

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• OOP design for DMS that allows searching and grouping

  - by James P.

  I'd like to make a searchable Document Management System and allow a user to group documents together. On one hand, there would be a functionality that registers/fingerprints in a linear fashion and, on the other, one that associates documents into groups. How could I compromise between the two in terms of object design?

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• Questions about "casting operation" in OOP

  - by rhapsodyn

  When programming, we usually use some type-casting operations. When the casting happens on the objects "on the same level", it feels ok. But when it happens on the ojects "on the different levels"(mainly between father and son), it feels weird. Considering this: Class Son extends Father WhenSon s = (Son)father;, it's absolutely unreasonable. Because a "Son" is not a "Father" anymore, "Son" may grow up with some new properties "Father" doesn't have, the casting operation makes these properties unknown. On the other hand, Father f = (Father)son seems reasonable, but according to LSP "An instance of a derived should be able to replace any instance of its superclass" A "Son" can do anything his "Father" can, so the casting operation seems useless. So can i say that these casting operations are agaisnt OO design principle but necessary?

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• Where to store frequently used functions in a OOP correct way

  - by Stefan Kuijers

  I'm working on a project which I want to build up OO. Now I came with a function that checks or a value is valid. private function valid(value:*, acceptedValues:Array):Boolean { for(var i:uint = 0; i < acceptedValues.length; i++) { if (value == acceptedValues[i]) { return true; } } return false; } As you can see, the function is very general and will be accessed across different classes. Now my question is; where do I store it in a OO correct way? Thanks in advance!

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• PHP OOP: method?

  - by Isis

  Hello <?php class Templater { static $params = array(); public static function assign($name, $value) { self::$params[] = array($name => $value); } public static function draw() { self::$params; } } $test = Templater::assign('key', 'value'); $test = Templater::draw(); print_r($test); How to alter this script so I could use this:? $test = Templater::assign('key', 'value')->assign('key2', 'value2')-draw(); print_r($test);

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• Javascript Event in Innerhtml Resulting from PHP Server Script

  - by user144527

  I'm (very slowly) making a website, and I'm creating a search engine for the database, which is essential to organize the dependencies during data entry. Anyway, what I would like is to type a few keywords into a box, have a menu pop up with various search results, and have the box fill with the ID number of the selected entry when it's clicked. Currently, I have a document called search.php which fills a div called search-output using xmlhttp.open() and the innerhtml property. Everything is working perfectly except for filling the original search box with the ID number when clicking. My first attempt was to add an onclick event to each entry in the output from search.php. Unfortunately, I found that javascript inserted into innerhtml is not run for security reasons. I've been Googling for hours but haven't been able to find a solution. How can I get the original search text box to fill with the correct ID when I click it? Is what I'm doing a good setup for the results I desire, or is there a better way to integrate search features into data entry?

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• Choosing a JavaScript Asynch-Loader

  - by Prisoner ZERO

  I’ve been looking at various asynchronous resource-loaders and I’m not sure which one to use yet. Where I work we have disparate group-efforts whose class-modules may use different versions of jQuery (etc). As such, nested dependencies may differ, as well. I have no control over this, so this means I need to dynamically load resources which may use alternate versions of the same library. As such, here are my requirements: Load JavaScript and CSS resource files asynchronously. Manage dependency-order and nested-dependencies across versions. Detect if a resource is already loaded. Must allow for cross-domain loading (CDN's) (optional) Allow us to unload a resource. I’ve been looking at: Curl RequireJS JavaScriptMVC LABjs I might be able to fake these requirements myself by loading versions into properly-namespaced variables & using an array to track what is already loaded...but (hopefully) someone has already invented this. So my questions are: Which ones do you use? And why? Are there others that my satisfy my requirements fully? Which do you find most eloquent and easiest to work with? And why?

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• C++ OOP - Can you 'overload a cast' <- hard to explain in 1 sentence

  - by Brandon Miller

  Well, the WinAPI has a POINT struct, but I am trying to make an alternative class to this so you can set the values of x and y from a constructor. /** * X-Y coordinates */ class Point { public: int X, Y; Point(void) : X(0), Y(0) {} Point(int x, int y) : X(x), Y(y) {} Point(const POINT& pt) : X(pt.x), Y(pt.y) {} Point& operator= (const POINT& other) { X = other.x; Y = other.y; } }; // I have an assignment operator and copy constructor. Point myPtA(3,7); Point myPtB(8,5); POINT pt; pt.x = 9; pt.y = 2; // I can assign a 'POINT' to a 'Point' myPtA = pt; // But I also want to be able to assign a 'Point' to a 'POINT' pt = myPtB; Is it possible to overload operator= in a way so that I can assign a Point to a POINT? Or maybe some other method to achieve this? Thanks in advance.

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• PHP OOP: Unique method per argument type?

  - by sunwukung

  I'm writing a little homebrew ORM (academic interest). I'm trying to adhere to the TDD concept as a training exercise, and as part of that exercise I'm writing documentation for the API as I develop the class. Case in point - I'm working on a classic "getCollection" type mapper class. I want it to be able to retrieve collections of asset X (let's say blog posts) for a specific user, and also collections based on an arbitrary array of numeric values. So - you might have a method like any one of these $User = $UserMapper->load(1); $ArticleCollection = $ArticleMapper->getCollection(range(10,20)); $ArticleCollection = $ArticleMapper->getCollection($User); $ArticleCollection = $ArticleMapper->getCollection($User->getId()); So, in writing the documentation for the getCollection method - I want to declare the @param variable in the Docblock. Is it better to have a unique method for each argument type, or is it acceptable to have a method that delegates to the correct internal method/class based on argument type?

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