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• cocoa - making a class like UIButton

  - by Mike

  For some reason that will take too much time to explain, I have to create a UIImageView based class that has some properties of a button. Imagine a class like the UISwitch (no I cannot base my class on the UISwitch) with two states, on and off. WHen the user selects one state, it runs a method like a button that was clicked and the method receives the sender id. I have already the class more or less working. The class is based on UIImageView. I am having difficulties to understand the following. WHen I create a new button I have a line that is like [myButton addTarget:self action:NSSelectorFromString(myMethod) forControlEvents:UIControlEventTouchUpInside]; This line defines a target and an action to run when the button is triggered. I my case I would need something like [myObject addTarget:self action:myMethod ifState:1] //or another thing ifState:2 I have no idea what kind of code I should put on the class to make this work. Remember that as a button the class should send the "sender" information to identify the object which triggered the action... Can you guys, transcendental gurus help? thanks.

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• Accessing a class's containing namespace from within a module

  - by SFEley

  I'm working on a module that, among other things, will add some generic 'finder' type functionality to the class you mix it into. The problem: for reasons of convenience and aesthetics, I want to include some functionality outside the class, in the same scope as the class itself. For example: class User include MyMagicMixin end # Should automagically enable: User.name('Bob') # Returns first user named Bob Users.name('Bob') # Returns ALL users named Bob User(5) # Returns the user with an ID of 5 Users # Returns all users I can do the functionality within these methods, no problem. And case 1 (User.name('Bob')) is easy. Cases 2–4, however, require being able to create new classes and methods outside User. The Module.included method gives me access to the class, but not to its containing scope. There is no simple "parent" type method that I can see on Class nor Module. (For namespace, I mean, not superclass nor nested modules.) The best way I can think to do this is with some string parsing on the class's #name to break out its namespace, and then turn the string back into a constant. But that seems clumsy, and given that this is Ruby, I feel like there should be a more elegant way. Does anyone have ideas? Or am I just being too clever for my own good?

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• Accessing type members outside the class in Scala

  - by Pekka Mattila

  Hi, I am trying to understand type members in Scala. I wrote a simple example that tries to explain my question. First, I created two classes for types: class BaseclassForTypes class OwnType extends BaseclassForTypes Then, I defined an abstract type member in trait and then defined the type member in a concerete class: trait ScalaTypesTest { type T <: BaseclassForTypes def returnType: T } class ScalaTypesTestImpl extends ScalaTypesTest { type T = OwnType override def returnType: T = { new T } } Then, I want to access the type member (yes, the type is not needed here, but this explains my question). Both examples work. Solution 1. Declaring the type, but the problem here is that it does not use the type member and the type information is duplicated (caller and callee). val typeTest = new ScalaTypesTestImpl val typeObject:OwnType = typeTest.returnType // declare the type second time here true must beTrue Solution 2. Initializing the class and using the type through the object. I don't like this, since the class needs to be initialized val typeTest = new ScalaTypesTestImpl val typeObject:typeTest.T = typeTest.returnType // through an instance true must beTrue So, is there a better way of doing this or are type members meant to be used only with the internal implementation of a class?

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• JQuery collapse table cells based on class

  - by H4mm3rHead

  Hi i have a table strcture for my menu, and i need to be able to collapse/expand the menu from level2, so that all level3 cells becone visible. My HTML is like this: <table> <tr><td class="level1"><a href="abc.html">First Item</a></td></tr> <tr><td class="level2"><a href="def.html">SecondItem</a></td></tr> <tr><td class="level3"><a href="ghi.html">Third Item</a></td></tr> <tr><td class="level3"><a href="jkl.html">Fourth Item</a></td></tr> <tr><td class="level3"><a href="mno.html">Fifth Item</a></td></tr> <tr><td class="level2"><a href="pqr.html">Sixth Item</a></td></tr> <tr><td class="level2"><a href="stu.html">Seventh Item</a></td></tr> </table> How do i, when i press the level2 item i only collapse/expand the level3 items following the level2 i pushed? I only want to do this for level2, not for level 1.

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• OnContextMenu() not working in view class

  - by Anu

  Hi, i have a popup menu for contextmenu.And i wrote the function for each menu in CMainframe. I have OnContextMenu() in each view class and in one dialog class.Its works fine in Dialog class.But not in View class.Codings are below: CMainframe funciton: void CMainFrame::OnUpdateFptrend(CCmdUI* pCmdUI) { ((CMainFrame *)AfxGetMainWnd())->SendMessage(WM_COMMAND,ID_TRENDVIEW,NULL); } void CMainFrame::OnUpdateFptuning(CCmdUI* pCmdUI) { ((CMainFrame *)AfxGetMainWnd())->SendMessageWM_COMMAND,ID_TUNINGVIEW,NULL); } Dialog class Contextmenu: void CFacePlate::OnContextMenu(CWnd* pWnd, CPoint point) { CMenu mnuPopup; mnuPopup.LoadMenu(IDR_FPMENU); CRect rBarRect; rBarRect.left = rBarRect.top = 0; rBarRect.right = 1000;rBarRect.bottom = 300; CMenu *mnuPopupMenu = mnuPopup.GetSubMenu(0); ASSERT(mnuPopupMenu); if( rBarRect.PtInRect(point) ) mnuPopupMenu->TrackPopupMenu(TPM_LEFTALIGN | TPM_RIGHTBUTTON, point.x, point.y, this); } View class: void CGroupView::OnContextMenu(CWnd* pWnd, CPoint point) { CMenu mnuPopup; mnuPopup.LoadMenu(IDR_FPMENU); CRect rBarRect; rBarRect.left = rBarRect.top = 0; rBarRect.right = 1150;rBarRect.bottom = 390; CMenu *mnuPopupMenu = mnuPopup.GetSubMenu(0); ASSERT(mnuPopupMenu); if( rBarRect.PtInRect(point) ) mnuPopupMenu->TrackPopupMenu(TPM_LEFTALIGN | TPM_RIGHTBUTTON, point.x, point.y, this); } When i press popup menu from Faceplate(Dialogclass),it goes to Mainframe function.At the same time when i press menu from any view class,it doesnot go to Mainframe function.Why its like that?

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• jQuery element with multiple classes: storing one class as a var

  - by Aaron

  I'm trying to create a standardized show/hide element system, like so: <div class="opener popup_1">Click Me</div> <div class="popup popup_1">I'm usually hidden</div> Clicking on the div with the opener class should show() the div with the popup class. I don't know how many opener/popup combinations I'm going to have on any given page, I don't know where on any given page the opener and the popup are going to be displayed, and I don't know how many popups a given opener should call show() for. Both the opener and the popup have to be able to have more classes than just what's used by jQuery. What I'd like to do is something like this: $(".opener").click(function() { var openerTarget = $(this).attr("class").filter(function() { return this.class.match(/^popup_([a-zA-Z0-9-_\+]*) ?$/); }); $(".popup." + openerTarget).show(); The idea is that when you click on an opener, it filters out "popup_whatever" from opener's classes and stores that as openerTarget. Then anything with class=popup and openerTarget will be shown.

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• c++ passing unknown type to a function and any Class type definition

  - by user259789

  I am trying to create a generic class to write and read Objects to/from file. Called it ActiveRecord class only has one method, which saves the class itself: void ActiveRecord::saveRecord(){ string fileName = "data.dat"; ofstream stream(fileName.c_str(), ios::out); if (!stream) { cerr << "Error opening file: " << fileName << endl; exit(1); } stream.write(reinterpret_cast<const char *> (this), sizeof(ActiveRecord)); stream.close(); } now I'm extending this class with User class: class User : public ActiveRecord { public: User(void); ~User(void); string name; string lastName; }; to create and save the user I would like to do something like: User user = User(); user.name = "John"; user.lastName = "Smith" user.save(); how can I get this ActiveRecord::saveRecord() method to take any object, and class definition so it writes whatever i send it: to look like: void ActiveRecord::saveRecord(foo_instance, FooClass){ string fileName = "data.dat"; ofstream stream(fileName.c_str(), ios::out); if (!stream) { cerr << "Error opening file: " << fileName << endl; exit(1); } stream.write(reinterpret_cast<const char *> (foo_instance), sizeof(FooClass)); stream.close(); } and while we're at it, what is the default Object type in c++. eg. in objective-c it's id in java it's Object in AS3 it's Object what is it in C++??

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• Correct way of setting a custom FileInfo class to an Iterator

  - by Gordon

  I am trying to set a custom class to an Iterator through the setInfoClass method: Use this method to set a custom class which will be used when getFileInfo and getPathInfo are called. The class name passed to this method must be derived from SplFileInfo. My class is like this (simplified example): class MyFileInfo extends SplFileInfo { public $props = array( 'foo' => '1', 'bar' => '2' ); } The iterator code is this: $rit = new RecursiveIteratorIterator( new RecursiveDirectoryIterator('/some/file/path/'), RecursiveIteratorIterator::SELF_FIRST); Since RecursiveDirectoryIterator is by inheritance through DirectoryIterator also an SplFileInfo object, it provides the setInfoClass method (it's not listed in the manual, but reflection shows it's there). Thus I can do: $rit->getInnerIterator()->setInfoClass('MyFileInfo'); All good up to here, but when iterating over the directory with foreach($rit as $file) { var_dump( $file ); } I get the following weird result object(MyFileInfo)#4 (3) { ["props"]=>UNKNOWN:0 ["pathName":"SplFileInfo":private]=>string(49) "/some/file/path/someFile.txt" ["fileName":"SplFileInfo":private]=>string(25) "someFile.txt" } So while MyFileInfo is picked up, I cannot access it's properties. If I add custom methods, I can invoke them fine, but any properties are UNKNOWN. If I don't set the info class to the iterator, but to the SplFileInfo object (like shown in the example in the manual), it will give the same UNKNOWN result: foreach($rit as $file) { // $file is a SplFileInfo instance $file->setInfoClass('MyFileInfo'); var_dump( $file->getFileInfo() ); } However, it will work when I do foreach($rit as $file) { $file = new MyFileInfo($file); var_dump( $file ); } Unfortunately, the code I a want to use this in is somewhat more complicated and stacks some more iterators. Creating the MyFileInfo class like this is not an option. So, does anyone know how to get this working or why PHP behaves this weird? Thanks.

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• How to control CSS class applied to ASP.NET 4 Menu with RenderingMode=List

  - by Joe

  I am using an ASP.NET 4.0 Menu control with RenderingMode=List and am struggling with creating the appropriate CSS. Each menu item is represented by an <li tag that contains a nested <a tag with what appear to be fixed class names: <a class="level1" for unselected level 1 menu items <a class="level2" for unselected level 2 menu items <a class="level1 selected" for the selected level 1 menu item ... etc... What I want to do is to is to prevent the currently selected menu item from being "clickable". To do so I tried using: if (menuItem.Selected) menuItem.Selectable = false; This has the desired effect of removing the href attribute from the <a tag but also removes the class attribute - and as a result my CSS can not identify what level the menu item belongs to! Looks to me like a possible bug, but in any case I can't find any documentation describing what CSS class names are used, nor whether there is any way to control this (the old Style properties don't appear to have any effect). Ideally I would like to have "level" class attributes on the <li tags, not just the nested <a tags.

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• NoClassDefFoundError without any class name

  - by Safder

  Hello, I am trying to run a java task from ant. I am trying to run the "org.apache.tools.ant.launch.Launcher" class. I keep on getting the "NoClassDefFoundError" without any class name being specified. I am also getting a "ClassNotFoundException" along with that displaying a message "Could not find the main class: . Program will exit". Here's a snippet of the error [java] Exception in thread "main" java.lang.NoClassDefFoundError: [java] Caused by: java.lang.ClassNotFoundException: [java] at java.net.URLClassLoader$1.run(URLClassLoader.java:200) [java] at java.security.AccessController.doPrivileged(Native Method) [java] at java.net.URLClassLoader.findClass(URLClassLoader.java:188) [java] at java.lang.ClassLoader.loadClass(ClassLoader.java:307) [java] at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) [java] at java.lang.ClassLoader.loadClass(ClassLoader.java:252) [java] at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) [java] Could not find the main class: . Program will exit. [java] Java Result: 1 Now I am trying to run an ant class from an ant jar and i specifiy the classpath where this class file resides using the "classpathref" attribute, however I still get this message. I checked the ant jar to check the Manifest and the "main" class is specified properly (it's "org.apache.tools.ant.launch.Launcher") . I have exhausted all my resources. Please help ! ! ! ps: My environment is Eclipse on Ubuntu 9.04

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• c# delegate and abstract class

  - by BeraCim

  Hi all: I currently have 2 concrete methods in 2 abstract classes. One class contains the current method, while the other contains the legacy method. E.g. // Class #1 public abstract class ClassCurrent<T> : BaseClass<T> where T : BaseNode, new() { public List<T> GetAllRootNodes(int i) { //some code } } // Class #2 public abstract class MyClassLegacy<T> : BaseClass<T> where T : BaseNode, new() { public List<T> GetAllLeafNodes(int j) { //some code } } I want the corresponding method to run in their relative scenarios in the app. I'm planning to write a delegate to handle this. The idea is that I can just call the delegate and write logic in it to handle which method to call depending on which class/project it is called from (at least thats what I think delegates are for and how they are used). However, I have some questions on that topic (after some googling): 1) Is it possible to have a delegate that knows the 2 (or more) methods that reside in different classes? 2) Is it possible to make a delegate that spawns off abstract classes (like from the above code)? (My guess is a no, since delegates create concrete implementation of the passed-in classes) 3) I tried to write a delegate for the above code. But I'm being technically challenged: public delegate List GetAllNodesDelegate(int k); GetAllNodesDelegate del = new GetAllNodesDelegate(ClassCurrent.GetAllRootNodes); I got the following error: An object reference is required for the non-static field, method, property ClassCurrent<BaseNode>.GetAllRootNodes(int) I might have misunderstood something... but if I have to manually declare a delegate at the calling class, AND to pass in the function manually as above, then I'm starting to question whether delegate is a good way to handle my problem. Thanks.

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• templete class c++

  - by inna karpasas

  hi! i try to design a templete for my universty project. i wrote the follwing cod: #ifndef _LinkedList_H_ #define _LinkedList_H_ #include "Link.h" #include <ostream> template <class L>//error one class LinkedList { private: Link<L> *pm_head; Link<L> * pm_tail; int m_numOfElements; Link<L>* FindLink(L * dataToFind); public: LinkedList(); ~LinkedList(); int GetNumOfElements(){return m_numOfElements;} bool Add( L * data); L *FindData(L * data); template <class L> friend ostream & operator<<(ostream& os,const LinkedList<L> listToprint);//error two L* GetDataOnTop(); bool RemoveFromHead(); L* Remove(L * toRemove); this templete uses the link class templete #ifndef _Link_H_ #define _Link_H_ template <class T>//error 3 class Link { private: T* m_data; Link* m_next; Link* m_prev; public: Link(T* data); ~Link(void); bool Link::operator ==(const Link& other)const; /*getters*/ Link* GetNext()const {return m_next;} Link* GetPrev()const {return m_prev;} T* GetData()const {return m_data;} //setters void SetNext(Link* next) {m_next = next;} void SetPrev(Link* prev) {m_prev = prev;} void SetData(T* data) {m_data = data;} }; error one: shadows template parm class L' error two:declaration ofclass L' error three: shadows template parm `class T' i dont understand what is the problem. i can relly usr your help thank you :)

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• The new operator in C# isn't overriding base class member

  - by Dominic Zukiewicz

  I am confused as to why the new operator isn't working as I expected it to. Note: All classes below are defined in the same namespace, and in the same file. This class allows you to prefix any content written to the console with some provided text. public class ConsoleWriter { private string prefix; public ConsoleWriter(string prefix) { this.prefix = prefix; } public void Write(string text) { Console.WriteLine(String.Concat(prefix,text)); } } Here is a base class: public class BaseClass { protected static ConsoleWriter consoleWriter = new ConsoleWriter(""); public static void Write(string text) { consoleWriter.Write(text); } } Here is an implemented class: public class NewClass : BaseClass { protected new static ConsoleWriter consoleWriter = new ConsoleWriter("> "); } Now here's the code to execute this: class Program { static void Main(string[] args) { BaseClass.Write("Hello World!"); NewClass.Write("Hello World!"); Console.Read(); } } So I would expect the output to be Hello World! > Hello World! But the output is Hello World Hello World I do not understand why this is happening. Here is my thought process as to what is happening: The CLR calls the BaseClass.Write() method The CLR initialises the BaseClass.consoleWriter member. The method is called and executed with the BaseClass.consoleWriter variable Then The CLR calls the NewClass.Write() The CLR initialises the NewClass.consoleWriter object. The CLR sees that the implementation lies in BaseClass, but the method is inherited through The CLR executes the method locally (in NewClass) using the NewClass.consoleWriter variable I thought this is how the inheritance structure works? Please can someone help me understand why this is not working?

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• Unit Testing Private Method in Resource Managing Class (C++)

  - by BillyONeal

  I previously asked this question under another name but deleted it because I didn't explain it very well. Let's say I have a class which manages a file. Let's say that this class treats the file as having a specific file format, and contains methods to perform operations on this file: class Foo { std::wstring fileName_; public: Foo(const std::wstring& fileName) : fileName_(fileName) { //Construct a Foo here. }; int getChecksum() { //Open the file and read some part of it //Long method to figure out what checksum it is. //Return the checksum. } }; Let's say I'd like to be able to unit test the part of this class that calculates the checksum. Unit testing the parts of the class that load in the file and such is impractical, because to test every part of the getChecksum() method I might need to construct 40 or 50 files! Now lets say I'd like to reuse the checksum method elsewhere in the class. I extract the method so that it now looks like this: class Foo { std::wstring fileName_; static int calculateChecksum(const std::vector<unsigned char> &fileBytes) { //Long method to figure out what checksum it is. } public: Foo(const std::wstring& fileName) : fileName_(fileName) { //Construct a Foo here. }; int getChecksum() { //Open the file and read some part of it return calculateChecksum( something ); } void modifyThisFileSomehow() { //Perform modification int newChecksum = calculateChecksum( something ); //Apply the newChecksum to the file } }; Now I'd like to unit test the calculateChecksum() method because it's easy to test and complicated, and I don't care about unit testing getChecksum() because it's simple and very difficult to test. But I can't test calculateChecksum() directly because it is private. Does anyone know of a solution to this problem?

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• MyController class must produce class according to the enum type.

  - by programmerist

  GenoTipController must produce class according to the enum type. i have 3 class: _Company,_Muayene,_Radyoloji. Also i have CompanyView Class GetPersonel method. if you look GenoTipController my codes need refactoring. Can you understand me? i need a class according to ewnum type must me produce class. For example; case DataModelType.Radyoloji it must return radyoloji= new Radyoloji . Everything must be one switch case? public class GenoTipController { public _Company GenerateCompany(DataModelType modeltype) { _Company company = null; switch (modeltype) { case DataModelType.Radyoloji: break; case DataModelType.Satis: break; case DataModelType.Muayene: break; case DataModelType.Company: company = new Company(); break; default: break; } return company; } public _Muayene GenerateMuayene(DataModelType modeltype) { _Muayene muayene = null; switch (modeltype) { case DataModelType.Radyoloji: break; case DataModelType.Satis: break; case DataModelType.Muayene: muayene = new Muayene(); break; case DataModelType.Company: break; default: break; } return muayene; } public _Radyoloji GenerateRadyoloji(DataModelType modeltype) { _Radyoloji radyoloji = null; switch (modeltype) { case DataModelType.Radyoloji: radyoloji = new Radyoloji(); break; case DataModelType.Satis: break; case DataModelType.Muayene: break; case DataModelType.Company: break; default: break; } return radyoloji; } } public class CompanyView { public static List GetPersonel() { GenoTipController controller = new GenoTipController(); _Company company = controller.GenerateCompany(DataModelType.Company); return company.GetPersonel(); } } public enum DataModelType { Radyoloji, Satis, Muayene, Company } }

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• Object Design: How to Organize/Structure a "Collection Class"

  - by CrimsonX

  I'm currently struggling to understand how I should organize/structure a class which I have already created. The class does the following: As its input in the constructor, it takes a collection of logs In the constructor it validates and filters the logs through a series of algorithms implementing my business logic After all filtering and validation is complete, it returns a collection (a List) of the valid and filtered logs which can be presented to the user graphically in a UI. Here is some simplified code describing what I'm doing: class FilteredCollection { public FilteredCollection( SpecialArray<MyLog> myLog) { // validate inputs // filter and validate logs in collection // in end, FilteredLogs is ready for access } Public List<MyLog> FilteredLogs{ get; private set;} } However, in order to access this collection, I have to do the following: var filteredCollection = new FilteredCollection( secialArrayInput ); //Example of accessing data filteredCollection.FilteredLogs[5].MyLogData; Other key pieces of input: I foresee only one of these filtered collections existing in the application (therefore should I make it a static class? Or perhaps a singleton?) Testability and flexibility in creation of the object is important (Perhaps therefore I should keep this an instanced class for testability?) I'd prefer to simplify the dereferencing of the logs if at all possible, as the actual variable names are quite long and it takes some 60-80 characters to just get to the actual data. My attempt in keeping this class simple is that the only purpose of the class is to create this collection of validated data. I know that there may be no "perfect" solution here, but I'm really trying to improve my skills with this design and I would greatly appreciate advice to do that. Thanks in advance.

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• jquery append 'x' number images elements applying 'x' to src and class

  - by Yusaf

  I have a directory with 590 pictures and my issue is being able to pull images using jquery alone from that directory and appending them which i have found out can not be done alone using jquery/javascript. alternatively i have renamed the pictures 1.jpg,2.jpg ... 590.jpg . how using jquery can i append 590 images to a div leaving me with the number of the appended element applied to the src being 'lq'+numberofappended+'.jpg' and class being 'image-'+numberofappended as a result leaving me with the below <div class="imagecontainer"> <img src="lq/1.jpg" class="image-1"/> <img src="lq/2.jpg" class="image-2"/> <img src="lq/3.jpg" class="image-3"/> ... <img src="lq/590.jpg" class="image-590"/> </div> if what I have will be too extensive can i append 50 images at a time and apply a jquery pagination loading another 50 each time i reach the end of the page. I personally know how to use append in jquery but I don't know how to individually append an image and depending on which append number it is applying it to the src and class.

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• C++ Pointer member function with templates assignment with a member function of another class

  - by Agusti

  Hi, I have this class: class IShaderParam{ public: std::string name_value; }; template<class TParam> class TShaderParam:public IShaderParam{ public: void (TShaderParam::*send_to_shader)( const TParam&,const std::string&); TShaderParam():send_to_shader(NULL){} TParam value; void up_to_shader(); }; typedef TShaderParam<float> FloatShaderParam; typedef TShaderParam<D3DXVECTOR3> Vec3ShaderParam; In another class, I have a vector of IShaderParams* and functions that i want to send to "send_to_shader". I'm trying assign the reference of these functions like this: Vec3ShaderParam *_param = new Vec3ShaderParam; _param-send_to_shader = &TShader::setVector3; This is the function: void TShader::setVector3(const D3DXVECTOR3 &vec, const std::string &name){ //... } And this is the class with IshaderParams*: class TShader{ std::vector params; public: Shader effect; std::string technique_name; TShader(std::string& afilename):effect(NULL){}; ~TShader(); void setVector3(const D3DXVECTOR3 &vec, const std::string &name); When I compile the project with Visual Studio C++ Express 2008 I recieve this error: Error 2 error C2440: '=' :can't make the conversion 'void (__thiscall TShader::* )(const D3DXVECTOR3 &,const std::string &)' a 'void (__thiscall TShaderParam::* )(const TParam &,const std::string &)' c:\users\isagoras\documents\mcv\afoc\shader.cpp 127 Can I do the assignment? No? I don't know how :-S Yes, I know that I can achieve the same objective with other techniques, but I want to know how can I do this..

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• Class Generics break completely seperate method

  - by TheLQ

  I found a strange problem when I used class Generics Today: Setting some broke a completely separate method. Here's a small example class that illustrates the problem. This code works just fine public class Sandbox { public interface ListenerManagerTest { public Set<Listener> getListeners(); } public void setListenerManager(ListenerManagerTest listenerManager) { for (Listener curListener : listenerManager.getListeners()) return; } } Now as soon as I use class Generics, the getListeners() method returns Set<Object> instead of Set<Listener> public class Sandbox { public interface ListenerManagerTest<E extends Object> { public Set<Listener> getListeners(); } public void setListenerManager(ListenerManagerTest listenerManager) { for (Listener curListener : listenerManager.getListeners()) //Expected Listener, not Object return; } } What would cause this error? The ##java channel on Freenode said it was because of compile time candy and that I was using a raw type. But how would an raw class type break all generics in the class? And how would of worked before?

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• Improve this generic abstract class

  - by Keivan

  I have the following abstract class design, I was wondering if anyone can suggest any improvements in terms of stronger enforcement of our requirements or simplifying implementing of the ControllerBase. //Dependency Provider base public abstract class ControllerBase<TContract, TType> where TType : TContract, class { public static TContract Instance { get { return ComponentFactory.GetComponent<TContract, TType>(); } } public TContract GetComponent<TContract, TType>() where TType : TContract, class { component = (TType)Activator.CreateInstance(typeof(TType), true); RegisterComponentInstance<TContract>(component); } } //Contract public interface IController { void DoThing(); } //Actual Class Logic public class Controller: ControllerBase<IController,Controller> { public void DoThing(); //internal constructor internal Controller(){} } //Usage public static void Main() { Controller.Instance.DoThing(); } The following facts should always be true, TType should always implement TContract (Enforced using a generic constraint) TContract must be an interface (Can't find a way to enforce it) TType shouldn't have public constructor, just an internal one, is there any way to Enforce that using ControllerBase? TType must be an concrete class (Didn't include New() as a generic constrain since the constructors should be marked as Internal)

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• Which class should store the lookup table?

  - by max

  The world contains agents at different locations, with only a single agent at any location. Each agent knows where he's at, but I also need to quickly check if there's an agent at a given location. Hence, I also maintain a map from locations to agents. I have a problem deciding where this map belongs to: class World, class Agent (as a class attribute) or elsewhere. In the following I put the lookup table, agent_locations, in class World. But now agents have to call world.update_agent_location every time they move. This is very annoying; what if I decide later to track other things about the agents, apart from their locations - would I need to add calls back to the world object all across the Agent code? class World: def __init__(self, n_agents): # ... self.agents = {} self.agent_locations = {} for id in range(n_agents): x, y = self.find_location() agent = Agent(self,x,y) self.agents.append(agent) self.agent_locations[x,y] = agent def update_agent_location(self, agent, x, y): del self.agent_locations[agent.x, agent.y] self.agent_locations[x, y] = agent def update(self): # next step in the simulation for agent in self.agents: agent.update() # next step for this agent # ... class Agent: def __init__(self, world, x, y): self.world = world self.x, self.y = x, y def move(self, x1, y1): self.world.update_agent_location(self, x1, y1) self.x, self.y = x1, y1 def update(): # find a good location that is not occupied and move there for x, y in self.valid_locations(): if not self.location_is_good(x, y): continue if self.world.agent_locations[x, y]: # location occupied continue self.move(x, y) I can instead put agent_locations in class Agent as a class attribute. But that only works when I have a single World object. If I later decide to instantiate multiple World objects, the lookup tables would need to be world-specific. I am sure there's a better solution... EDIT: I added a few lines to the code to show how agent_locations is used. Note that it's only used from inside Agent objects, but I don't know if that would remain the case forever.

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• Simple matrix example using C++ template class

  - by skyeagle

  I am trying to write a trivial Matrix class, using C++ templates in an attempt to brush up my C++, and also to explain something to a fellow coder. This is what I have som far: template class<T> class Matrix { public: Matrix(const unsigned int rows, const unsigned int cols); Matrix(const Matrix& m); Matrix& operator=(const Matrix& m); ~Matrix(); unsigned int getNumRows() const; unsigned int getNumCols() const; template <class T> T getCellValue(unsigned int row, unsigned col) const; template <class T> void setCellValue(unsigned int row, unsigned col, T value) const; private: // Note: intentionally NOT using smart pointers here ... T * m_values; }; template<class T> inline T Matrix::getCellValue(unsigned int row, unsigned col) const { } template<class T> inline void Matrix::setCellValue(unsigned int row, unsigned col, T value) { } I'm stuck on the ctor, since I need to allocate a new[] T, it seems like it needs to be a template method - however, I'm not sure I have come accross a templated ctor before. How can I implemnt the ctor?

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• Jersey, JAXB and getting an objectextending an abstract class as a parameter

  - by krajol

  I want to get an object as a parameter of a POST request. I got an abstract superclass that is called Promotion and subclasses Product and Percent. Here's how I try to get a request: @POST @Consumes(MediaType.APPLICATION_XML) @Produces(MediaType.APPLICATION_XML) @Path("promotion/") public Promotion createPromotion(Promotion promotion) { Product p = (Product) promotion; System.out.println(p.getPriceAfter()); return promotion; } and here's how I use JAXB in classes' definitions: @XmlRootElement(name="promotion") @XmlSeeAlso({Product.class,Percent.class}) public abstract class Promotion { //body } @XmlRootElement(name="promotion") public class Product extends Promotion { //body } @XmlRootElement(name="promotion") public class Percent extends Promotion { //body } So the problem now is when I send a POST request with a body like this: <promotion> <priceBefore>34.5</priceBefore> <marked>false</marked> <distance>44</distance> </promotion> and I try to cast it to Product (as in this case, fields 'marked' and 'distance' are from Promotion class and 'priceBefore' is from Product class) I get an Exception: java.lang.ClassCastException: Percent cannot be cast to Product. It seems like Percent is chosen as a 'default' subclass. Why is that and how can I get an object that is a Product?

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• C++: defining maximum/minimum limits for a class

  - by Luis

  Basically what the title says... I have created a class that models time slots in a variable-granularity daily schedule (where for example the first time slot is 30 minutes, but the second time slot can be 40 minutes); the first available slot starts at (a value comparable to) 1. What I want to do now is to define somehow the maximum and minimum allowable values that this class takes and I have two practical questions in order to do so: 1.- does it make sense to define absolute minimum and maximum in such a way for a custom class? Or better, does it suffice that a value always compares as lower-than any other possible value of the type, given the class's defined relational operators, to be defined the min? (and analogusly for the max) 2.- assuming the previous question has an answer modeled after "yes" (or "yes but ..."), how do I define such max/min? I know that there is std::numeric_limits<> but from what I read it is intended for "numeric types". Do I interpret that as meaning "represented as a number" or can I make a broader assumption like "represented with numbers" or "having a correspondence to integers"? After all, it would make sense to define the minimum and maximum for a date class, and maybe for a dictionary class, but numeric_limits may not be intended for those uses (I don't have much experience with it). Plus, numeric_limits has a lot of extra members and information that I don't know what to make with. If I don't use numeric_limits, what other well-known / widely-used mechanism does C++ offer to indicate the available range of values for a class?

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• Java extends classes - Share the extended class fields within the super class.

  - by Bastan

  Straight to the point... I have a class public class P_Gen{ protected String s; protected Object oP_Gen; public P_Gen(String str){ s = str; oP_Gen = new Myclass(this); } } Extended class: public class P extends P_Gen{ protected Object oP; public P(String str){ oP = new aClass(str); super(str); } } MyClass: public class MyClass{ protected Object oMC; public MyClass(P extendedObject){ oMc = oP.getSomething(); } } I came to realize that MyClass can only be instantiated with (P_Gen thisObject) as opposed to (P extendedObject). The situation is that I have code generated a bunch of classes like P_Gen. For each of them I have generated a class P which would contains my P specific custom methods and fields. When I'll regenerate my code in the future, P would not be overwritten as P_Gen would. ** So what happened in my case???!!!... I realized that MyClass would beneficiate from the info stored in P in addition to only P_Gen. Would that possible? I know it's not JAVA "realistic" since another class that extends P_Gen might not have the same fields... BY DESIGN, P_Gen will not be extended by anything but P.... And that's where it kinda make sens. :-) at least in other programming language ;-) In other programming language, it seems like P_Gen.this === P.this, in other word, "this" becomes a combination of P and P_Gen. Is there a way to achieve this knowing that P_Gen won't be extended by anything than P?

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