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• pass by reference or pass by value?

  - by Sven

  When learning a new programming language, one of the possible roadblocks you might encounter is the question whether the language is, by default, pass-by-value or pass-by-reference So here is my question to all of you, in your favorite language, how is it actually done? and what are the possible pitfalls? your favorite language can, of course, be anything you have ever played with: popular, obscure, esoteric, new, old ...

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• Is this the correct way of speaking to a "Content Manager" Class?

  - by DeanMc

  I am creating a silverlight site. I am currently breaking out my ideas into pieces of functionality. One of the idea's I have is the concept of a content manager. This is essentially a UI control with 4 regions. Top, Bottom, Right & Left. I also have a collection of objects that are considered "Menu Items". These are controls that function as a way to navigate around, similar to links. The idea I have is to implement an IMenuItem interface. Among the standard pieces of information (Text, PageReference, etc) I was also going to hold a reference to the content manager. My idea behind this thinking is that I can pass the PageReference to a property on the ContentManager and then call a method which knows how to update the content manager accordingly. Is this the best way of implementing this or is their some sort of pattern for it?

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• Progress Bar design patterns?

  - by shoosh

  The application I'm writing performs a length algorithm which usually takes a few minutes to finish. During this time I'd like to show the user a progress bar which indicates how much of the algorithm is done as precisely as possible. The algorithm is divided into several steps, each with its own typical timing. For instance- initialization (500 milli-sec) reading inputs (5 sec) step 1 (30 sec) step 2 (3 minutes) writing outputs (7 sec) shutting down (10 milli-sec) Each step can report its progress quite easily by setting the range its working on, say [0 to 150] and then reporting the value it completed in its main loop. What I currently have set up is a scheme of nested progress monitors which form a sort of implicit tree of progress reporting. All progress monitors inherit from an interface IProgressMonitor: class IProgressMonitor { public: void setRange(int from, int to) = 0; void setValue(int v) = 0; }; The root of the tree is the ProgressMonitor which is connected to the actual GUI interface: class GUIBarProgressMonitor : public IProgressMonitor { GUIBarProgressMonitor(ProgressBarWidget *); }; Any other node in the tree are monitors which take control of a piece of the parent progress: class SubProgressMonitor : public IProgressMonitor { SubProgressMonitor(IProgressMonitor *parent, int parentFrom, int parentLength) ... }; A SubProgressMonitor takes control of the range [parentFrom, parentFrom+parentLength] of its parent. With this scheme I am able to statically divide the top level progress according to the expected relative portion of each step in the global timing. Each step can then be further subdivided into pieces etc' The main disadvantage of this is that the division is static and it gets painful to make changes according to variables which are discovered at run time. So the question: are there any known design patterns for progress monitoring which solve this issue?

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• Class Design - Returning a List<Object> From <Object>

  - by Mike

  Given a simple class: public class Person { public string FirstName; public string LastName; public string GetFullName() { return FirstName + LastName; } } The user of this class will populate a List<Person> object by reading an Xml file or some other data source. Should the logic for populating the List be in the Person class or should it just remain in the calling class? In other words, should there be a public List<Persons> GetPersons() method in the Person class or in the calling class? Or should the data accessor be in another class altogether? I know this is a rather simplistic question but I'm just curious how others typically do it.

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• what is factory in php and how it can be useful?

  - by Avinash

  Hi I just want to know that what is the factory in php? And how can I use it in my code? Are there and benefits and drawbacks of it? Thanks Avinash

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• Strategy pattern and "action" classes explosion

  - by devoured elysium

  Is it bad policy to have lots of "work" classes(such as Strategy classes), that only do one thing? Let's assume I want to make a Monster class. Instead of just defining everything I want about the monster in one class, I will try to identify what are its main features, so I can define them in interfaces. That will allow to: Seal the class if I want. Later, other users can just create a new class and still have polymorphism by means of the interfaces I've defined. I don't have to worry how people (or myself) might want to change/add features to the base class in the future. All classes inherit from Object and they implement inheritance through interfaces, not from mother classes. Reuse the strategies I'm using with this monster for other members of my game world. Con: This model is rigid. Sometimes we would like to define something that is not easily achieved by just trying to put together this "building blocks". public class AlienMonster : IWalk, IRun, ISwim, IGrowl { IWalkStrategy _walkStrategy; IRunStrategy _runStrategy; ISwimStrategy _swimStrategy; IGrowlStrategy _growlStrategy; public Monster() { _walkStrategy = new FourFootWalkStrategy(); ...etc } public void Walk() { _walkStrategy.Walk(); } ...etc } My idea would be next to make a series of different Strategies that could be used by different monsters. On the other side, some of them could also be used for totally different purposes (i.e., I could have a tank that also "swims"). The only problem I see with this approach is that it could lead to a explosion of pure "method" classes, i.e., Strategy classes that have as only purpose make this or that other action. In the other hand, this kind of "modularity" would allow for high reuse of stratagies, sometimes even in totally different contexts. What is your opinion on this matter? Is this a valid reasoning? Is this over-engineering? Also, assuming we'd make the proper adjustments to the example I gave above, would it be better to define IWalk as: interface IWalk { void Walk(); } or interface IWalk { IWalkStrategy WalkStrategy { get; set; } //or something that ressembles this } being that doing this I wouldn't need to define the methods on Monster itself, I'd just have public getters for IWalkStrategy (this seems to go against the idea that you should encapsulate everything as much as you can!) Why? Thanks

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• Using generics with XmlSerializer

  - by MainMa

  Hi, When using XML serialization in C#, I use code like this: public MyObject LoadData() { XmlSerializer xmlSerializer = new XmlSerializer(typeof(MyObject)); using (TextReader reader = new StreamReader(settingsFileName)) { return (MyObject)xmlSerializer.Deserialize(reader); } } (and similar code for deserialization). It requires casting and is not really nice. Is there a way, directly in .NET Framework, to use generics with serialization? That is to say to write something like: public MyObject LoadData() { // Generics here. XmlSerializer<MyObject> xmlSerializer = new XmlSerializer(); using (TextReader reader = new StreamReader(settingsFileName)) { // No casts nevermore. return xmlSerializer.Deserialize(reader); } }

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• Concrete Types or Interfaces for return types?

  - by SDReyes

  Today I came to a fundamental paradox of the object programming style, concrete types or interfaces. Whats the better election for a method's return type: a concrete type or an interface? In most cases, I tend to use concrete types as the return type for methods. because I believe that an concrete type is more flexible for further use and exposes more functionality. The dark side of this: Coupling. The angelic one: A concrete type contains per-se the interface you would going to return initially, and extra functionality. What's your thumb's rule? Is there any programming principle for this? BONUS: This is an example of what I mean http://stackoverflow.com/questions/491375/readonlycollection-or-ienumerable-for-exposing-member-collections

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• abstract class extends abstract class in php?

  - by user151841

  I am working on a simple abstract database class. In my usage of this class, I'll want to have some instance be a singleton. I was thinking of having a abstract class that is not a singleton, and then extend it into another abstract class that is a singleton. Is this possible? Recommended?

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• call parent constructor in ruby

  - by Stas

  Hi! How can I call parents constructor ? module C attr_accessor :c, :cc def initialization c, cc @c, @cc = c, cc end end class B attr_accessor :b, :bb def initialization b, bb @b, @bb = b, bb end end class A < B include C attr_accessor :a, :aa def initialization (a, b, c, aa, bb, cc) #call B::initialization - ? #call C::initialization - ? @a, @aa = a, aa end end Thanks.

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• Why is Self assignable in Delphi?

  - by mjustin

  This code in a GUI application compiles and runs: procedure TForm1.Button1Click(Sender: TObject); begin Self := TForm1.Create(Owner); end; (tested with Delphi 6 and 2009) why is Self writeable and not read-only? in which situations could this be useful? Edit: is this also possible in Delphi Prism? (I think yes it is, see here) Update: Delphi applications/libraries which make use of Self assignment: python4delphi

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• Avoiding RTTI In Java

  - by destructo_gold

  Hi, If I have a superclass, say Animal, and two subclasses: Zebra and Giraffe, If I decide to define a Vector of Animals: Vector <Animal> animals = new Vector(); and I want to say: You can add Giraffes, but you must own at least one Zebra first. What is the best way to do this without using RTTI? (instanceof)

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• Inheritance using prototype / "new"

  - by mikkol

  Hi I'm new in Javascript OO and want to know more about about inheritance. Hope you can provide some advice! I see this great post: How to "properly" create a custom object in JavaScript? which talks about how a class is inherited as I see in other websites, ex.: function man(x) { this.x = x; this.y = 2; } man.prototype.name = "man"; man.prototype.two = function() { this.y = "two"; } function shawn() { man.apply(this, arguments); }; shawn.prototype = new man; The above post claims that in order not to call "man"'s constructor while inheriting, one can use a helper like this instead: function subclassOf(base) { _subclassOf.prototype= base.prototype; return new _subclassOf(); } function _subclassOf() {}; shawn.prototype = subclassOf(man); While I understand its intention, I don't see why we can't call shawn.prototype = man.prototype; I see it works exactly the same. Or is there something I'm missing? Thanks in advance!

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• Do fluent interfaces violate the Law of Demeter?

  - by Jakub Šturc

  The wikipedia article about Law of Demeter says: The law can be stated simply as "use only one dot". However a simple example of a fluent interface may look like this: static void Main(string[] args) { new ZRLabs.Yael.Pipeline("cat.jpg") .Rotate(90) .Watermark("Monkey") .RoundCorners(100, Color.Bisque) .Save("test.png"); } So does this goes together?

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• MVC pattern and (Game) State pattern

  - by topright

  Game States separate I/O processing, game logic and rendering into different classes: while (game_loop) { game->state->io_events(this); game->state->logic(this); game->state->rendering(); } You can easily change a game state in this approach. MVC separation works in more complex way: while (game_loop) { game->cotroller->io_events(this); game->model->logic(this); game->view->rendering(); } So changing Game States becomes error prone task (switch 3 classes, not 1). What are practical ways of combining these 2 concepts?

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• Extending a singleton class

  - by cakyus

  i used to create an instance of a singleton class like this: $Singleton = SingletonClassName::GetInstance(); and for non singleton class: $NonSingleton = new NonSingletonClassName; i think we should not differentiate how we create an instance of a class whether this is a singleton or not. if i look in perception of other class, i don't care whether the class we need a singleton class or not. so, i still not comfortable with how php treat a singleton class. i think and i always want to write: $Singleton = new SingletonClassName; just another non singleton class, is there a solution to this problem ?

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• Trouble with inheritance

  - by Matt

  I'm relatively new to programming so excuse me if I get some terms wrong (I've learned the concepts, I just haven't actually used most of them). Trouble: I currently have a class I'll call Bob its parent class is Cody, Cody has method call Foo(). I want Bob to have the Foo() method as well, except with a few extra lines of code. I've attempted to do Foo() : base(), however that doesn't seem to work like. Is there some simple solution to this?

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• Help organising controllers logically

  - by kenny99

  Hi guys, I'm working on a site which i'm developing using an MVC structure. My models will represent all of data in the site, but i'm struggling a bit to decide on a good controller structure. The site will allow users to login/register and see personal data on a number of pages, but also still have access to public pages, e.g FAQs, Contact page etc. This is what I have at the moment... A Template Controller which handles main template display. The basic template for the site will remain the same whether or not you are logged in. A main Website Controller which extends the Template Controller and handles basic authentication. If the user is logged in, a User::control_panel() method is called from the constructor and this builds the control panel which will be present throughout the authenticated session. If user is not logged in, then a different view is loaded instead of the control panel, e.g with a login form. All protected/public page related controllers will extend the website controller. The user homepage has a number of widgets I want to display, which I'm doing via a Home Controller which extends the Website Controller. This controller generates these widgets via the following static calls: $this->template->content->featured_pet = Pet::featured(); $this->template->content->popular_names = Pet::most_popular(); $this->template->content->owner_map = User::generate_map(); $this->template->content->news = News::snippet(); I suppose the first thing I'm unsure about is if the above static calls to controllers (e.g Pet and User) are ok to remain static - these static methods will return views which are loaded into the main template. This is the way I've done things in the past but I'm curious to find out if this is a sensible approach. Other protected pages for signed in users will be similar to the Home Controller. Static pages will be handled by a Page Controller which will also extend the Website Controller, so that it will know whether or not the user control panel or login form should be shown on the left hand side of the template. The protected member only pages will not be routed to the Page Controller, this controller will only handle publicly available pages. One problem I have at the moment, is that if both public and protected pages extend the Website Controller, how do I avoid an infinite loop - for example, the idea is that the website controller should handle authentication then redirect to the requested controller (URL), but this will cause an infinite redirect loop, so i need to come up with a better way of dealing with this. All in all, does this setup make any sense?! Grateful for any feedback.

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• Ruby Abstract Class Design

  - by MattDiPasquale

  I'm creating a video game. It has Characters & Items. Since I want Characters & Items to each have a name, should I make another class called NamedObjects with just a name field and have Characters & Items extend that? Or is that going overboard?

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• define constant in php

  - by jera

  how do I define a constant inside a function eg. class { public test; function tester{ const test = "abc"; } }

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• Unable to compare valuesfrom mysql in a prepared statement

  - by Cortopasta

  I can't seem to get this to connect to the database so that I can run my prepared statement. Does anybody have an idea what I've forgotten? private function check_credentials($plain_username, $password) { global $dbcon; $ac = new ac(); $ac->dbconnect(); $userid = $dbcon->prepare('SELECT id FROM users WHERE username = :username AND password = :password LIMIT 1'); $userid->bindParam(':username', $plain_username); $userid->bindParam(':password', $password); $userid->execute(); $id = $userid->fetch(); Return $id; } EDIT: I changed the SQL query from a SELECT FROM query, to an INSERT INTO query and it worked. WHat the heck is going on?

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• Proper way to set class variables

  - by ensnare

  I'm writing a class to insert users into a database, and before I get too far in, I just want to make sure that my OO approach is clean: class User(object): def setName(self,name): #Do sanity checks on name self._name = name def setPassword(self,password): #Check password length > 6 characters #Encrypt to md5 self._password = password def commit(self): #Commit to database >>u = User() >>u.setName('Jason Martinez') >>u.setPassword('linebreak') >>u.commit() Is this the right approach? Should I declare class variables up top? Should I use a _ in front of all the class variables to make them private? Thanks for helping out.

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• Assigning property to JS object using another objects property value as the property name

  - by hamstar

  Hey guys, I want to use the value of an objects property to name the property of another object. Easy to do in PHP: $object1->property = 'name'; $object2->{$object1->property} = "value"; echo $object2->name; //outputs "value" But in Javascript I can't figure out how to do this. The curly braces are used a different way. Anyone know the php equivalent in javascript? Thanks :)

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• nesting classes in php

  - by Honey

  here is my sample class to why i want to nest. include("class.db.php"); class Cart { function getProducts() { //this is how i do it now. //enter code here`but i dont want to redeclare for every method in this class. //how can i declare it in one location to be able to use the same variable in every method? $db = new mysqlDB; $query = $db->query("select something from a table"); return $query } }

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• PHP: Proper way of using a PDO database connection in a class

  - by Cortopasta

  Trying to organize all my code into classes, and I can't get the database queries to work inside a class. I tested it without the class wrapper, and it worked fine. Inside the class = no dice. What about my classes is messing this up? class ac { public function dbConnect() { global $dbcon; $dbInfo['server'] = "localhost"; $dbInfo['database'] = "sn"; $dbInfo['username'] = "sn"; $dbInfo['password'] = "password"; $con = "mysql:host=" . $dbInfo['server'] . "; dbname=" . $dbInfo['database']; $dbcon = new PDO($con, $dbInfo['username'], $dbInfo['password']); $dbcon->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); $error = $dbcon->errorInfo(); if($error[0] != "") { print "<p>DATABASE CONNECTION ERROR:</p>"; print_r($error); } } public function authentication() { global $dbcon; $plain_username = $_POST['username']; $md5_password = md5($_POST['password']); $ac = new ac(); if (is_int($ac->check_credentials($plain_username, $md5_password))) { ?> <p>Welcome!</p> <!--go to account manager here--> <?php } else { ?> <p>Not a valid username and/or password. Please try again.</p> <?php unset($_POST['username']); unset($_POST['password']); $ui = new ui(); $ui->start(); } } private function check_credentials($plain_username, $md5_password) { global $dbcon; $userid = $dbcon->prepare('SELECT id FROM users WHERE username = :username AND password = :password LIMIT 1'); $userid->bindParam(':username', $plain_username); $userid->bindParam(':password', $md5_password); $userid->execute(); print_r($dbcon->errorInfo()); $id = $userid->fetch(); Return $id; } } And if it's any help, here's the class that's calling it: require_once("ac/acclass.php"); $ac = new ac(); $ac->dbconnect(); class ui { public function start() { if ((!isset($_POST['username'])) && (!isset($_POST['password']))) { $ui = new ui(); $ui->loginform(); } else { $ac = new ac(); $ac->authentication(); } } private function loginform() { ?> <form id="userlogin" action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post"> User:<input type="text" name="username"/><br/> Password:<input type="password" name="password"/><br/> <input type="submit" value="submit"/> </form> <?php } }

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