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  • objective C architecture question

    - by thekevinscott
    Hey folks, I'm currently teaching myself objective C. I've gone through the tutorials, but I find I learn best when slogging through a project of my own, so I've embarked on making a backgammon app. Now that I'm partway in, I'm realizing there's some overall architecture things I just don't understand. I've established a "player" class, a "piece" class, and a "board" class. A piece theoretically belongs to both a player and the board. For instance, a player has a color, and every turn makes a move; so the player owns his pieces. At the same time, when moving a piece, it has to check whether it's a valid move, whether there are pieces on the board, etc. From my reading it seems like it's frowned upon to reach across classes. For instance, when a player makes a move, where should the function live that moves the piece? Should it exist on board? This would be my instinct, as the board should decide whether a move is valid or not; but the piece needs to initialize that query, as its the one being moved, no? Any info to help a noob would be super appreciated. Thanks guys!

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  • CakePHP form $options['options']

    - by James
    Hey! Total CakePHP noob here. This is sort of a two fold question. In a view that is used for adding user objects I would like to use a drop down (selection) field in the form. Each user belongs to a group so when I add a user I want a drop down that contains all of the groups that the user could possibly join. Currently the group_id field is a textfield. I know how to force it to be a selection field, but I don't know how to populate the selection with the names of the groups programmatically. The Current method: echo $form->input('group_id', array( '1' => 'NameOfGroup1', '2' => 'NameOfGroup2', '3' => 'NameOfGroup3') ); I want to generate the options array programmatically though. echo $form->input('group_id', $this->Group->find('list')); This doesn't work though. I get an error: Undefined property: View::$Group [APP/views/users/add.ctp, line 8] To me this means that I don't have access to the Group object from inside my user view. How can I accomplish this? Again, I want to do it programmatically so that it updates as I add groups or remove them.

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  • PHP: Get instance of static class by string value

    - by Tirithen
    I'm working on a php web api that was handed to me with a lot of code that needs to be refactored. The ones that wrote the code wanted to include a static configuration class to an api resource and then get an instance of that class something like this: <?php $obj = "User"; $confObjectSuffix = "_conf"; $confObject = $obj.$confObjectSuffix; if ($confObject::inst()->checkMethod($method)) { ..... This gives the error "Parse error: syntax error, unexpected T_PAAMAYIM_NEKUDOTAYIM in ....." since $confObject is a string and not a object. I wrote some testcode: <?php $class = "User_conf"; echo "<pre>"; print_r($$class::Inst()); echo "</pre>"; class User_conf { private static $INSTANCE = null; public static function Inst() { if(User_conf::$INSTANCE === null) { User_conf::$INSTANCE = new User_conf(); } return User_conf::$INSTANCE; } } But can't get it to work with $$ either, is there some other way around this? I don't want to rewrite more than necessary.

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  • iPhone Dev: Animating PNG Sequences

    - by Franky
    What is the best or recommended technique for animating PNG Sequences. Heres what I've learned: Do it Manually Using MutableArrays containing Strings, you can animate a UIImageView with a timer which increments an index number UIImage - animation methods This works, the only problem is to find if an image has completed its animation, you have to check the isAnimating BOOL, and to do that you need a timer. What is the best and recommended? Looking to do Oldschool game sprite animations, ie: Idle Animation Attack Animation Walk Animation ect... Let me know if any one has something. @lessfame

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  • Implementation question involving implementing an interface

    - by Vivin Paliath
    I'm writing a set of collection classes for different types of Trees. I'm doing this as a learning exercise and I'm also hoping it turns out to be something useful. I really want to do this the right way and so I've been reading Effective Java and I've also been looking at the way Joshua Bloch implemented the collection classes by looking at the source. I seem to have a fair idea of what is being done, but I still have a few things to sort out. I have a Node<T> interface and an AbstractNode<T> class that implements the Node interface. I then created a GenericNode<T> (a node that can have 0 to n children, and that is part of an n-ary tree) class that extends AbstractNode<T> and implements Node<T>. This part was easy. Next, I created a Tree<T> interface and an AbstractTree<T> class that implements the Tree<T> interface. After that, I started writing a GenericTree<T> class that extends AbstractTree<T> and implements Tree<T>. This is where I started having problems. As far as the design is concerned, a GenericTree<T> can only consist of nodes of type GenericTreeNode<T>. This includes the root. In my Tree<T> interface I have: public interface Tree<T> { void setRoot(Node<T> root); Node<T> getRoot(); List<Node<T>> postOrder(); ... rest omitted ... } And, AbstractTree<T> implements this interface: public abstract class AbstractTree<T> implements Tree<T> { protected Node<T> root; protected AbstractTree() { } protected AbstractTree(Node<T> root) { this.root = root; } public void setRoot(Node<T> root) { this.root = root; } public Node<T> getRoot() { return this.root; } ... rest omitted ... } In GenericTree<T>, I can have: public GenericTree(Node<T> root) { super(root); } But what this means is that you can create a generic tree using any subtype of Node<T>. You can also set the root of a tree to any subtype of Node<T>. I want to be able to restrict the type of the node to the type of the tree that it can represent. To fix this, I can do this: public GenericTree(GenericNode<T> root) { super(root); } However, setRoot still accepts a parameter of type Node<T>. Which means a user can still create a tree with the wrong type of root node. How do I enforce this constraint? The only way I can think of doing is either: Do an instanceof which limits the check to runtime. I'm not a huge fan of this. Remove setRoot from the interface and have the base class implement this method. This means that it is not part of the contract and anyone who wants to make a new type of tree needs to remember to implement this method. Is there a better way? The second question I have concerns the return type of postOrder which is List<Node<T>>. This means that if a user is operating on a GenericTree<T> object and calls postOrder, he or she receives a list that consists of Node<T> objects. This means when iterating through (using a foreach construct) they would have perform an explicit cast to GenericNode<T> if they want to use methods that are only defined in that class. I don't like having to place this burden on the user. What are my options in this case? I can only think of removing the method from the interface and have the subclass implement this method making sure that it returns a list of appropriate subtype of Node<T>. However, this once again removes it from the contract and it's anyone who wants to create a new type of tree has to remember to implement this method. Is there a better way?

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  • JavaScript check if anonymous object has a method

    - by Baddie
    How can I check if an anonymous object that was created as such: var myObj = { prop1: 'no', prop2: function () { return false; } } does indeed have a prop2 defined? prop2 will always be defined as a function, but for some objects it is not required and will not be defined. I tried what was suggested here: http://stackoverflow.com/questions/595766/how-to-determine-if-native-javascript-object-has-a-property-method but I don't think it works for anonymous objects .

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  • OO Design / Patterns - Fat Model Vs Transaction Script?

    - by ben
    Ok, 'Fat' Model and Transaction Script both solve design problems associated with where to keep business logic. I've done some research and popular thought says having all business logic encapsulated within the model is the way to go (mainly since Transaction Script can become really complex and often results in code duplication). However, how does this work if I want to use the TDG of a second Model in my business logic? Surely Transaction Script presents a neater, less coupled solution than using one Model inside the business logic of another? A practical example... I have two classes: User & Alert. When pushing User instances to the database (eg, creating new user accounts), there is a business rule that requires inserting some default Alerts records too (eg, a default 'welcome to the system' message etc). I see two options here: 1) Add this rule as a User method, and in the process create a dependency between User and Alert (or, at least, Alert's Table Data Gateway). 2) Use a Transaction Script, which avoids the dependency between models. (Also, means the business logic is kept in a 'neutral' class & easily accessible by Alert. That probably isn't too important here, though). User takes responsibility for it's own validation etc, however, but because we're talking about a business rule involving two Models, Transaction Script seems like a better choice to me. Anyone spot flaws with this approach?

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  • can you explain this jquery method from jquery.js

    - by mrblah
    Trying to understand how jquery works under the covers, what's the difference between: jQuery.fn and jQuery.prototype jQuery = window.jQuery = window.$ = function( selector, context ) { // The jQuery object is actually just the init constructor 'enhanced' return new jQuery.fn.init( selector, context ); }, and then: jQuery.fn = jQuery.prototype = { init: function( selector, context ) {

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  • Why is execution-time method resolution faster than compile-time resolution?

    - by Felix
    At school, we about virtual functions in C++, and how they are resolved (or found, or matched, I don't know what the terminology is -- we're not studying in English) at execution time instead of compile time. The teacher also told us that compile-time resolution is much faster than execution-time (and it would make sense for it to be so). However, a quick experiment would suggest otherwise. I've built this small program: #include <iostream> #include <limits.h> using namespace std; class A { public: void f() { // do nothing } }; class B: public A { public: void f() { // do nothing } }; int main() { unsigned int i; A *a = new B; for (i=0; i < UINT_MAX; i++) a->f(); return 0; } Where I made A::f() once normal, once virtual. Here are my results: [felix@the-machine C]$ time ./normal real 0m25.834s user 0m25.742s sys 0m0.000s [felix@the-machine C]$ time ./virtual real 0m24.630s user 0m24.472s sys 0m0.003s [felix@the-machine C]$ time ./normal real 0m25.860s user 0m25.735s sys 0m0.007s [felix@the-machine C]$ time ./virtual real 0m24.514s user 0m24.475s sys 0m0.000s [felix@the-machine C]$ time ./normal real 0m26.022s user 0m25.795s sys 0m0.013s [felix@the-machine C]$ time ./virtual real 0m24.503s user 0m24.468s sys 0m0.000s There seems to be a steady ~1 second difference in favor of the virtual version. Why is this? Relevant or not: dual-core pentium @ 2.80Ghz, no extra applications running between two tests. Archlinux with gcc 4.5.0. Compiling normally, like: $ g++ test.cpp -o normal Also, -Wall doesn't spit out any warnings, either.

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  • What's the deal with Java's public fields?

    - by Annan
    I've been reading two articles (1)(2) on javaworld.com about how all class fields should be private and getter/setter methods are just as bad. An object should act on the data it has rather than allowing access to it. I'm currently working on a University assignment for Connect Four. In designing the program the Agents playing the Game need access to the Board's state (so they can decide what to move). They also need to pass this move to the Game so it can validate it as a legal move. And during deciding what to move pieces are grouped into Threats with a start and end Points. Board, Threat and Point objects don't really do anything. They are just there to store related data that can be accessed in a human readable way. At the start of design I was representing Points on the board as two element int arrays, however that got annoying when creating points or referencing components of them. So, the class: public class Point { public int x; public int y; public Point(int x, int y){ this.x = x; this.y = y; } } Perfect in every way I can think of. Except it breaks every rule I've learned. Have I sinned?

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  • When should I use Dependency Injection and when utility methods?

    - by Roman
    I have a Java EE project with Spring IoC container. I've just found in Utils class static method sendMail(long list of params). I don't know why but I feel that it would look better if we had separate class (Spring bean with singleton scope) which will be responsible for sending email. But I can't find any arguments which can prove my position. So, are there any pros (or cons) in using DI in this (rather general) situation?

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  • How do I dynamically instantiate a class in javascript?

    - by Adam
    I'm starting out with classes in Javascript and have hit a wall. I've looked all over for a tutorial that goes a little further than simply how to construct a class (usually Animal) then extend the class and have a Method do something (Dog alert('Bark');). I have created a class that I want a user to be able to instantiate (is that the right word)? For example the first stage in my program is for the user to give the class a name, and then start to populate the various variables in the class. When they've done that they may do it again many times. So if: var className = new MyObject(); How do I dynamically create the name of the new object className and then refer to it later in the code?

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  • How Can I Learn about Interfaces

    - by BDotA
    I am using C# and I know what are the interfaces and how syntatically use them,etc. but what I have not learned yet is that when I am tasked to write a project, create a component,... How should I learn better about interfaces so when I want to do something I be able to Think about using them in my design...or for example I want to learn about dependency injection or even using mocking objects for testing, these are all related to good understanding of interfaces and know when and how to use them ... Can you plase provide me some good advice, reading,... then can help me with that?

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  • Single Responsibility Principle usage how can i call sub method correctly?

    - by Phsika
    i try to learn SOLID prencibles. i writed two type of code style. which one is : 1)Single Responsibility Principle_2.cs : if you look main program all instance generated from interface 1)Single Responsibility Principle_3.cs : if you look main program all instance genareted from normal class My question: which one is correct usage? which one can i prefer? namespace Single_Responsibility_Principle_2 { class Program { static void Main(string[] args) { IReportManager raporcu = new ReportManager(); IReport wordraporu = new WordRaporu(); raporcu.RaporHazirla(wordraporu, "data"); Console.ReadKey(); } } interface IReportManager { void RaporHazirla(IReport rapor, string bilgi); } class ReportManager : IReportManager { public void RaporHazirla(IReport rapor, string bilgi) { rapor.RaporYarat(bilgi); } } interface IReport { void RaporYarat(string bilgi); } class WordRaporu : IReport { public void RaporYarat(string bilgi) { Console.WriteLine("Word Raporu yaratildi:{0}",bilgi); } } class ExcellRaporu : IReport { public void RaporYarat(string bilgi) { Console.WriteLine("Excell raporu yaratildi:{0}",bilgi); } } class PdfRaporu : IReport { public void RaporYarat(string bilgi) { Console.WriteLine("pdf raporu yaratildi:{0}",bilgi); } } } Second 0ne all instance genareted from normal class namespace Single_Responsibility_Principle_3 { class Program { static void Main(string[] args) { WordRaporu word = new WordRaporu(); ReportManager manager = new ReportManager(); manager.RaporHazirla(word,"test"); } } interface IReportManager { void RaporHazirla(IReport rapor, string bilgi); } class ReportManager : IReportManager { public void RaporHazirla(IReport rapor, string bilgi) { rapor.RaporYarat(bilgi); } } interface IReport { void RaporYarat(string bilgi); } class WordRaporu : IReport { public void RaporYarat(string bilgi) { Console.WriteLine("Word Raporu yaratildi:{0}",bilgi); } } class ExcellRaporu : IReport { public void RaporYarat(string bilgi) { Console.WriteLine("Excell raporu yaratildi:{0}",bilgi); } } class PdfRaporu : IReport { public void RaporYarat(string bilgi) { Console.WriteLine("pdf raporu yaratildi:{0}",bilgi); } } }

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  • Proper way to set object instance 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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  • How can i use complextype class or multi type class is it generic collection?

    - by programmerist
    i need a complex returning type. i have 4 class returning types COMPLEXTYPE must include Company, Muayene, Radyoloji, Satis because i must return data switch case situation how can i do? Maybe i need generic collections How can i do that? public class GenoTipController { public COMPLEXTYPE Generate(DataModelType modeltype) { _Company company = null; _Muayene muayene = null; _Radyoloji radyoloji = null; _Satis satis = null; switch (modeltype) { case DataModelType.Radyoloji: radyoloji = new Radyoloji(); return radyoloji; break; case DataModelType.Satis: satis = new Satis(); return satis; break; case DataModelType.Muayene: muayene = new Muayene(); return muayene; break; case DataModelType.Company: company = new Company(); return company; break; default: break; } } } public class CompanyView { public static List GetPersonel() { GenoTipController controller = new GenoTipController(); _Company company = controller.Generate(DataModelType.Company); return company.GetPersonel(); } } public enum DataModelType { Radyoloji, Satis, Muayene, Company }

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  • My abstract class implements an interface but doesn't implement some of its methods. How do I make i

    - by Stefan Monov
    interface ICanvasTool { void Motion(Point newLocation); void Tick(); } abstract class CanvasTool_BaseDraw : ICanvasTool { protected abstract void PaintAt(Point location); public override void Motion(Point newLocation) { // implementation } } class CanvasTool_Spray : CanvasTool_BaseDraw { protected abstract void PaintAt(Point location) { // implementation } public override void Tick() { // implementation } } This doesn't compile. I could add an abstract method "Tick_Implementation" to CanvasTool_BaseDraw, then implement ICanvasTool.Tick in CanvasTool_BaseDraw with a one-liner that just calls Tick_Implementation. Is this the recommended workaround?

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  • Can you declare <canvas> methods within a template in javascript?

    - by Binarytales
    Not entirely sure I posed the question in the best way but here goes... I have been playing around with the HTML5 canvas API and have got as far as drawing a shape in the canvas and getting it to move around with the arrow keys. I then tried to move my various variables and functions to a template so I could spawn multiple shapes (that would eventually be controlled by different keys). This is what I have: function player(x, y, z, colour, speed){ this.lx = x; this.ly = y; this.speed = 10; this.playerSize = z; this.colour = colour; } playerOne = new player(100, 100, 10, "#F0F"); function persona(z, colour){ zone.fillStyle = colour; offset = 0 - (z / 2); zone.fillRect(offset, offset, z, z); } function move(x, y){ playerOne.lx = playerOne.lx + x; playerOne.ly = playerOne.ly + y; zone.clearRect(0, 0, 500, 500); zone.save(); zone.translate(playerOne.lx, playerOne.ly); persona(playerOne.playerSize, playerOne.colour); zone.restore(); } window.onkeydown = function() { var direction = this.event.keyCode; var s = playerOne.speed; // Arrow Keys if( direction == 38 && playerOne.ly >= 10){ // Up move(0,-s); } if( direction == 40 && playerOne.ly <= 490){ // Down move(0,s); } if( direction == 37 && playerOne.lx >= 10){ // Left move(-s,0); } if( direction == 39 && playerOne.lx <= 490){ // Right move(s,0); } }; window.onload = function() { zone = document.getElementById('canvas').getContext('2d'); zone.save(); zone.translate(playerOne.lx, playerOne.ly); persona(playerOne.playerSize, playerOne.colour); zone.restore(); }; So what I tried to do was move the persona function into the player template like this: function player(x, y, z, colour, speed){ this.lx = x; this.ly = y; this.speed = 10; function persona(){ zone.fillStyle = colour; var offset = 0 - (z / 2); zone.fillRect(offset, offset, z, z); } } And then where before it said persona(playerOne.playerSize, playerOne.colour); it now just says playerOne.persona(); But this is just totally flaking out and not working and I can't figure out why. I'm probably going about it all the wrong way and I think the problem is that I'm trying to manipulate the canvas.context (call zone in my script) from within a object/template. Perhaps its nothing to do with that at all and I an just not declaring my persona functions properly in the context of the template. Documentation for the canvas API is very thin on the ground and any hint in the right direction will be very much appreciated.

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  • Why this method does not use any properties of the object?

    - by Roman
    Here I found this code: import java.awt.*; import javax.swing.*; public class FunWithPanels extends JFrame { public static void main(String[] args) { FunWithPanels frame = new FunWithPanels(); frame.doSomething(); } void doSomething() { Container c = getContentPane(); JPanel p1 = new JPanel(); p1.setLayout(new BorderLayout()); p1.add(new JButton("A"), BorderLayout.NORTH); p1.add(new JButton("B"), BorderLayout.WEST); JPanel p2 = new JPanel(); p2.setLayout(new GridLayout(3, 2)); p2.add(new JButton("F")); p2.add(new JButton("G")); p2.add(new JButton("H")); p2.add(new JButton("I")); p2.add(new JButton("J")); p2.add(new JButton("K")); JPanel p3 = new JPanel(); p3.setLayout(new BoxLayout(p3, BoxLayout.Y_AXIS)); p3.add(new JButton("L")); p3.add(new JButton("M")); p3.add(new JButton("N")); p3.add(new JButton("O")); p3.add(new JButton("P")); c.setLayout(new BorderLayout()); c.add(p1, BorderLayout.CENTER); c.add(p2, BorderLayout.SOUTH); c.add(p3, BorderLayout.EAST); pack(); setVisible(true); } } I do not understand how "doSomething" use the fact that "frame" is an instance of the class JFrame. It is not clear to me because there is no reference to "this" in the code for the method "doSomething".

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