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  • Using C++, how to call a base class method from a derived class method and apply this to an object passed as an argument?

    - by Chris
    I can't figure out how to call a base class method from a derived class method but concurrently applying this method call at an object passed as argument. What I mean is this: class Animal { virtual void eat(Animal& to_be_eaten) = 0; }; class Carnivores: public Animal { virtual void eat(Animal& to_be_eaten) { /*implementation here*/} }; class Wolf : public Carnivores { virtual void eat(Animal& to_be_eaten) { /*call eat method(of Base class) of Base to_be_eaten here*/ } } I thought of something like this dynamic_cast<Carnivores&>(to_be_eaten).eat(*this) //and got a segmentation fault Is there any way for this to be done? Thank you! New edit:: Updated the code

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  • Abstract classes in shared library

    - by JTom
    Hi, I have an ordinary abstract class that has couple of pure virtual methods. The class itself is a part of the shared library. The compilation of the shared library itself is OK. But when the library is linked to another program that has another class deriving from the abstract one in the shared library and defining the pure virtual methods, I get the following linker error: I compile like this..: g++ -I../path/to/the/library main.cpp derived.cpp -L../path/to/the/library -lsomename -o shared ...and the linker error is: libsomename.so: undefined reference to `AbstractClass::method()' It's like the abstract class cannot access its pure virtual methods but I do not try to make any instance of the abstract class anywhere in the library. What could be the problem?

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  • API Class with intensive network requests

    - by Marco Acierno
    I'm working an API which works as "intermediary" between a REST API and the developer. In this way, when the programmer do something like this: User user = client.getUser(nickname); it will execute a network request to download from the service the data about the user and then the programmer can use the data by doing things like user.getLocation(); user.getDisplayName(); and so on. Now there are some methods like getFollowers() which execute another network request and i could do it in two ways: Download all the data in the getUser method (and not only the most important) but in this way the request time could be very long since it should execute the request to various urls Download the data when the user calls the method, it looks like the best way and to improve it i could cache the result so the next call to getFollowers returns immediately with the data already download instead of execute again the request. What is the best way? And i should let methods like getUser and getFollowers stop the code execution until the data is ready or i should implement a callback so when the data is ready the callback gets fired? (this looks like Javascript)

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  • MCP 1.7.10 Java class navigation

    - by Elias Benevedes
    So, I'm new to the Minecraft modding community and trying to understand where to start. I've attempted to do it before, but dropped it to the complexity of starting and the lack of a site like this to help (Mind that I'm also semi-new to Java, but have worked extensively in Javascript and Python. I understand how Java is different from the two). I have downloaded MCP 9.08 (Decompiles 1.7.10), and decompiled Minecraft. I'm looking to mod client, so I didn't supply it with a server jar. Everything seemed to work fine in decompile (Only error was it couldn't find the server jar). I can find my files in /mcp908/src/minecraft/net/minecraft. However, if I open up one of the classes in, say, block, I see a bunch of variables starting with p_ and ending with _. Is there any way to make these variables more decipherable, to understand what's going on so I can learn by example? Thank you.

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  • use jQuery to get 'true size' of image without removing the class

    - by jon3laze
    I am using Jcrop on an image that is resized with css for uniformity. JS <script type="text/javascript"> $(window).load(function() { //invoke Jcrop API and set options var api = $.Jcrop('#image', { onSelect: storeCoords, trueSize: [w, h] }); api.disable(); //disable until ready to use //enable the Jcrop on crop button click $('#crop').click(function() { api.enable(); }); }); function storeCoords(c) { $('#X').val(c.x); $('#Y').val(c.y); $('#W').val(c.w); $('#H').val(c.h); }; </script> HTML <body> <img src="/path/to/image.jpg" id="image" class="img_class" alt="" /> <br /> <span id="crop" class="button">Crop Photo</span> <span id="#X" class="hidden"></span> <span id="#Y" class="hidden"></span> <span id="#W" class="hidden"></span> <span id="#H" class="hidden"></span> </body> CSS body { font-size: 13px; width: 500px; height: 500px; } .image { width: 200px; height: 300px; } .hidden { display: none; } I need to set the h and w variables to the size of the actual image. I tried using the .clone() manipulator to make a copy of the image and then remove the class from the clone to get the sizing but it sets the variables to zeros. var pic = $('#image').clone(); pic.removeClass('image'); var h = pic.height(); var w = pic.width(); It works if I append the image to an element in the page, but these are larger images and I would prefer not to be loading them as hidden images if there is a better way to do this. Also removing the class, setting the variables, and then re-adding the class was producing sporadic results. I was hoping for something along the lines of: $('#image').removeClass('image', function() { h = $(this).height(); w = $(this).width(); }).addClass('image'); But the removeClass function doesn't work like that :P

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  • Instantiate proper class based on some input

    - by Adam Backstrom
    I'm attempting to understand how "switch as a code smell" applies when the proper code path is determined by some observable piece of data. My Webapp object sets an internal "host" object based on the hostname of the current request. Each Host subclass corresponds to one possible hostname and application configuration: WwwHost, ApiHost, etc. What is an OOP way for a host subclass to accept responsibility for a specific hostname, and for Webapp to get an instance of the appropriate subclass? Currently, the hostname check and Host instantiation exists within the Webapp object. I could move the test into a static method within the Host subclasses, but I would still need to explicitly list those subclasses in Webapp unless I restructure further. It seems like any solution will require new subclasses to be added to some centralized list.

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  • abstract class in C++

    - by Alexander
    I have a derived derived class from an abstract class. The code is below. I have a FishTank class which is derived from an Aquarium and Aquarium is derived from item. My question is that should I put the definition of virtual int minWidth() const = 0; in aquarium again or is the code below sufficient? class Item{ public: virtual int minWidth() const = 0; }; class Aquarium{ public: virtual int calWidth() = 0; // Pure virtual function. }; class FishTank : public Aquarium{ public: FishTank(int base1, int base2, int height); ~FishTank(); int calWidth(); int minWidth(); };

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  • propertyplaceholderconfigurer class name substitution problem

    - by Alex
    The following example works for "class name substitution using the PropertyPlaceHolderConfigurer": http://forum.springsource.org/showpost.php?p=228136&postcount=2 HOWEVER, when porting this code over (messages.properties, com.spring.ioc.TestClass, and spring-config.xml) to a web application, the class name substitution now fails! 1) I am running on the webapp on Tomcat through the Eclipse plugin. 2) In the web.xml I have the following: <context-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/spring-config.xml</param-value> </context-param> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> 3) The following is output in the log: 282 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Ignoring bean class loading failure for bean 'test' org.springframework.beans.factory.CannotLoadBeanClassException: Cannot find class [${test.class}] for bean with name 'test' defined in ServletContext resource [/WEB-INF/spring-config.xml]; nested exception is java.lang.ClassNotFoundException: ${test.class} at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1141) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:524) at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1177) at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:222) at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:505) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:362) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3795) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4252) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014) at org.apache.catalina.core.StandardHost.start(StandardHost.java:736) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:448) at org.apache.catalina.core.StandardServer.start(StandardServer.java:700) at org.apache.catalina.startup.Catalina.start(Catalina.java:552) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433) Caused by: java.lang.ClassNotFoundException: ${test.class} at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1438) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1284) at org.springframework.util.ClassUtils.forName(ClassUtils.java:211) at org.springframework.beans.factory.support.AbstractBeanDefinition.resolveBeanClass(AbstractBeanDefinition.java:385) at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1138) ... 23 more Note: I haven't included it, but the PropertyPlaceHolderConfigurer is successfully locating the messages.properties file, but this seems to happen AFTER the above error is output?! DOES ANYBODY KNOW WHY THIS IS THE CASE AND HOW I CAN OVERCOME THIS PROBLEM?

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  • When to use functional programming approach and when not? (in Java)

    - by john smith optional
    let's assume I have a task to create a Set of class names. To remove duplication of .getName() method calls for each class, I used org.apache.commons.collections.CollectionUtils and org.apache.commons.collections.Transformer as follows: Snippet 1: Set<String> myNames = new HashSet<String>(); CollectionUtils.collect( Arrays.<Class<?>>asList(My1.class, My2.class, My3.class, My4.class, My5.class), new Transformer() { public Object transform(Object o) { return ((Class<?>) o).getName(); } }, myNames); An alternative would be this code: Snippet 2: Collections.addAll(myNames, My1.class.getName(), My2.class.getName(), My3.class.getName(), My4.class.getName(), My5.class.getName()); So, when using functional programming approach is overhead and when it's not and why? Isn't my usage of functional programming approach in snippet 1 is an overhead and why?

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  • Objective-c class initializer executes multiple times

    - by apisip
    Unless I misunderstood it, this LINK from Apple's documentation clearly states that the class initializer, "+ (void)initialize)", only executes once per class. Here is the excerpt: Special Considerations initialize it is invoked only once per class. If you want to perform independent initialization for the class and for categories of the class, you should implement load methods. However, I'm getting a weird behavior on my project and the initializer is being executed twice. So I have to check if _classContext is null. I only got one class that has this method. What are the possible reasons why this is happening? I'm using XCode 4.5.2 and OS X 10.8.2. I got multiple iOS simulators, iPhone 5.1 and 6.0. + (void) initialize { num++; NSLog([NSString stringWithFormat:@"Times: %i", num]); if(_classContext == nil) _classContext = [[myClass alloc] init]; }

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  • Is the a pattern for iterating over lists held by a class (dynamicly typed OO languages)

    - by Roman A. Taycher
    If I have a class that holds one or several lists is it better to allow other classes to fetch those lists(with a getter) or to implement a doXList/eachXList type method for that list that take a function and call that function on each element of the list contained by that object. I wrote a program that did a ton of this and I hated passing around all these lists sometimes with method in class a calling method in class B to return lists contained in class C, B contains a C or multiple C's (note question is about dynamically typed OO languages languages like ruby or smalltalk) ex. (that came up in my program) on a Person class containing scheduling preferences and a scheduler class needing to access them.

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  • How to access the backing field of an inherited class using fluent nhibernate

    - by Akk
    How do i set the Access Strategy in the mapping class to point to the inherited _photos field? public class Content { private IList<Photo> _photos; public Content() { _photos = new List<Photo>(); } public virtual IEnumerable<Photo> Photos { get { return _photos; } } public virtual void AddPhoto() {...} } public class Article : Content { public string Body {get; set;} } I am currently using thw following to try and locate the backing field but an exception is thrown as it cannot be found. public class ArticleMap : ClassMap<Article> { HasManyToMany(x => x.Photos) .Access.CamelCaseField(Prefix.Underscore) //_photos //... } i tried moving the backing field _photos directly into the class and the access works. So how can i access the backing field of an inherited class?

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  • How should I declare default values for instance variables in Python?

    - by int3
    Should I give my class members default values like this: class Foo: num = 1 or like this? class Foo: def __init__(self): self.num = 1 In this question I discovered that in both cases, bar = Foo() bar.num += 1 is a well-defined operation. I understand that the first method will give me a class variable while the second one will not. However, if I do not require a class variable, but only need to set a default value for my instance variables, are both methods equally good? Or one of them more 'pythonic' than the other? One thing I've noticed is that in the Django tutorial, they use the second method to declare Models. Personally I think the second method is more elegant, but I'd like to know what the 'standard' way is.

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  • Expected Class-name before { token

    - by ML
    Hi All, I am trying to figure out whey I get an error: expected class-name before { token Here is the relative source to the error: #pragma once #ifndef H_FXACTION #define H_FXACTION #include "CP_M_RefCounted.h" #include "FxTypes.h" #include "string" #include "FxString.h" #include "FxPixels.h" #include "CP_Rect.h" #include "FxStreamable.h" #include "FxPoint.h" #include "FxPtr.h" #include "FxImage.h" #include "FxSleekStreaming.h" typedef FxID FxActionType; typedef FxUInt32 FxActionID; FxActionID FrMakeUniqueActionID(void); class FxActionData; class FxActionData : public CP_M_RefCounted { public: FxActionData(); FxActionData(FxBool final) :mFinal(final) { } virtual ~FxActionData(); I get the error at this line: class FxActionData : public CP_M_RefCounted What I dont get is why the line: class FxActionData; is there when you are creating the class directly under it. Isn't this a forward declaration? What things could be going on here?

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  • implement string class with custom behavior

    - by truman
    In one of our class sir said that template allows one to customize behavior of class, and then he gave example of string class, that with few lines of code we can customize string class from STL, as in, we can make it to treat 'a' and 'z' same, 'b' and 'y' same, 'c' and 'x' same and so on. Similary 'A' and 'Z' same etc. "abc" == "zyx" is true; "Abc" == "zyx" is false; "Abc == "Zyx" is true; etc I was thinking of implementing such string class, but I am not able to do so. How can we implement such string class using templates?

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  • boost::enable_if class template method

    - by aaa
    I got class with template methods that looks at this: struct undefined {}; template<typename T> struct is_undefined : mpl::false_ {}; template<> struct is_undefined<undefined> : mpl::true_ {}; template<class C> struct foo { template<class F, class V> typename boost::disable_if<is_undefined<C> >::type apply(const F &f, const V &variables) { } template<class F, class V> typename boost::enable_if<is_undefined<C> >::type apply(const F &f, const V &variables) { } }; apparently, both templates are instantiated, resulting in compile time error. is instantiation of template methods different from instantiation of free functions? I have fixed this differently, but I would like to know what is up. Thank you

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  • Creating An Utilities Class?

    - by Soo
    Hello SO, I'm very new to OOP and am trying my hardest to keep things strictly class based, while using good coding priciples. I'm a fair ways into my project now and I have a lot of general use methods I want to put into an utilities class. Is there a best way to create an utilities class? public class Utilities { int test; public Utilites() { } public int sum(int number1, int number2) { test = number1+number2; } return test; } After creating this Utilities class, do I just create an Utilities object, and run the methods of my choosing? Do I have this Utilities class idea correct?

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  • What is the best way to store meshes or 3d models in a class

    - by Robse
    I am wondering, how I should store my mesh into memory after loading it from whatever file. I have Questions floating in my head: Should a mesh could have sub meshes or does the 3d model just store a list of meshes all on the same level Is there one material assigned to one mesh 1:1? What do I have to consider, if I want to store skeletal animations? Btw it's a OpenGL|ES2 iOS game using GLKit. I came up with some basic struct types: (But I think they are way to simple and I need to add padding or change the vector3 to vector4.) typedef union _N3DShortVector2 { struct { short x, y; }; struct { short s, t; }; short v[2]; } N3DShortVector2; typedef union _N3DShortVector3 { struct { short x, y, z; }; struct { short r, g, b; }; struct { short s, t, p; }; short v[3]; } N3DShortVector3; typedef GLKVector3 N3DFloatVector3; typedef struct _N3DMeshRecordSV3 { N3DShortVector3 v1, v2, v3; } N3DMeshRecordSV3; typedef struct _N3DMeshRecordSV3FN3ST2 { N3DShortVector3 v1, v2, v3; N3DFloatVector3 n1, n2, n3; N3DShortVector2 t1, t2, t3; } N3DMeshRecordSV3FN3ST2;

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  • How access PhysicalMaterial from Actor Class?

    - by EmAdpres
    I use Projectile for my weapon system and UDKProjectile has two main function to handle Hit of projectiles(=bullet of my weapon): simulated function ProcessTouch(Actor Other, Vector HitLocation, Vector HitNormal) // For Actors simulated event HitWall(vector HitNormal, actor Wall, PrimitiveComponent WallComp) // Everything except Actors ( I guess) the first method, the function just give me the actor which I hit and my question is How I can get that actor's physical material by first parameter ( Other ), in order to make a proper react about it ( for example a proper Sound of collide ) ... A tricky (but hateful ) way which I knew works is, make a Trace from a little back of that actor to that actor, and use HitInfo parameter which include physical Material ! But there should be a more standard way !

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  • Define a class dynamically?

    - by Pekka
    Is there a way to dynamically and conditionally create a class definition in PHP, i.e. if (condition matches) include file containing class definition else class myclass extends ancestor_class { .................... } without eval()? My background is the accepted answer to this question. I am looking for the best way to build a untouchable core library, with user-defined empty classes extending the core library if necessary. I want to create the final class definition "on the fly" if there is no user-defined empty class for a certain ancestor class.

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  • ZF Autoloader to load ancestor and requested class

    - by Pekka
    I am integrating Zend Framework into an existing application. I want to switch the application over to Zend's autoloading mechanism to replace dozens of include() statements. I have a specific requirement for the autoloading mechanism, though. Allow me to elaborate. The existing application uses a core library (independent from ZF), for example: /Core/Library/authentication.php /Core/Library/translation.php /Core/Library/messages.php this core library is to remain untouched at all times and serves a number of applications. The library contains classes like class ancestor_authentication { ... } class ancestor_translation { ... } class ancestor_messages { ... } in the application, there is also a Library directory: /App/Library/authentication.php /App/Library/translation.php /App/Library/messages.php these includes extend the ancestor classes and are the ones that actually get instantiated in the application. class authentication extends ancestor_authentication { } class translation extends ancestor_translation { } class messages extends ancestor_messages { } usually, these class definitions are empty. They simply extend their ancestors and provide the class name to instantiate. $authentication = new authentication(); The purpose of this solution is to be able to easily customize aspects of the application without having to patch the core libraries. Now, the autoloader I need would have to be aware of this structure. When an object of the class authentication is requested, the autoloader would have to: 1. load /Core/Library/authentication.php 2. load /App/Library/authentication.php My current approach would be creating a custom function, and binding that to Zend_Loader_Autoloader for a specific namespace prefix. Is there already a way to do this in Zend that I am overlooking? The accepted answer in this question kind of implies there is, but that may be just a bad choice of wording. Are there extensions to the Zend Autoloader that do this? Can you - I am new to ZF - think of an elegant way, conforming with the spirit of the framework, of extending the Autoloader with this functionality? I'm not necessary looking for a ready-made implementation, some pointers (This should be an extension to the xyz method that you would call like this...) would already be enough.

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  • c# GUI changing a listbox from another class

    - by SlowForce
    I've written a multithreaded server that uses tcplistener and a client handler class that controls input and output. I also have a GUI chat client. The chat client works fine and the console version of the server also works well. I have a start() method in the partial(?) Form class, which I run from a new thread when I click a button, that starts the TCP Listener and loops through and accepts socket requests. For every request a new ClientHandler object is created and the socket is passed to this object before being used in a new handler thread. The ClientHandler is a different class to the form and I'm having real problems writing data to the Listbox in the Form class from within the ClientHandler class. I've tried a few different ways of doing this but none of them work as they involve creating a new form class within the ClientHandler. Any help or advice on what I should be reading to help me would be really appreciated.

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