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  • Question about factory classes

    - by devoured elysium
    Currently I have created a ABCFactory class that has a single method creating ABC objects. Now that I think of it, maybe instead of having a factory, I could just make a static method in my ABC Method. What are the pro's and con's on making this change? Will it not lead to the same? I don't foresee having other classes inherit ABC, but one never knows! Thanks

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  • Base class with abstract subclasses in C# ?

    - by Nick Brooks
    public abstract class Request { public class Parameters { //Threre are no members here //But there should be in inherited classes } public Request() { parameters = new Parameters(); } public Parameters parameters; } Two questions: How do I make it so I can add stuff to the constructor but the original constructor will still be executed? How do I make it so the subclasses can add members to the Parameters class?

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  • Java: Interface vs Abstract Class (regarding fields)

    - by lifeR00t
    From what I have gathered, I want to force a class to use particular private fields (and methods) I need an abstract class because an interface only declares public/static/final fields and methods. Correct?? I just started my first big java project and want to make sure I'm not going to hurt myself later :)

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  • Abstract classes and Pod::Coverage

    - by Ken Williams
    I've recently started to try to use Dist::Zilla for maintaining Path::Class. I added the [PodCoverageTests] plugin, and it's reporting some failures in the Path::Class::Entity class, which is the abstract base class for Path::Class::File and Path::Class::Dir. What I'd like is some way to tell the testing code that Entity doesn't need docs, but its two derived classes do - even though the methods are only defined in the parent class. Anyone know some way to do that?

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  • Rails 3 Abstract Class vs Inherited Class

    - by R. Yanchuleff
    In my rails 3 model, I have two classes: Product, Service. I want both to be of type InventoryItem because I have another model called Store and Store has_many :InventoryItems This is what I'm trying to get to, but I'm not sure how to model this in my InventoryItem model and my Product and Service models. Should InventoryItem just be a parent class that Product and Service inherit from, or should InventoryItem be modeled as a class abstract of which Product and Service extend from. Thanks in advance for the advice!

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  • can I have an abstract base class with the key attribute being generic

    - by Greg
    Hi, I want to create a re-usable library. I was going to use extension methods however I run into some issues in some cases for the client to have to specify in the calling method the types. QUESTION - If I use an abstract base class as the basis, can I specify an attribute/property in the class to be generic (e.g. the key property might be an 'int' in one case, or a 'string' in another)?

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  • Using java abstract class

    - by user969131
    In my UI project, I have few screens that share the same header style only the text is specific to the screens. What will be a good way to implement this? Have the super class create all the header component and open the components to the sub class, the sub class will access to component's setText method to update the text? or Have abstract method in super class to create the components, sub class will implement these methods to create the component. Hope it make sense..

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  • Why abstract classes necessary?

    - by bala3569
    1.What is the point of creating a class that can't be instantiated? Most commonly to serve as a base-class or interface (some languages have a separate interface construct, some don't) - it doesn't know the implementation (that is to be provided by the subclasses / implementing classes) 2.Why would anybody want such a class? For abstraction and re-use 3.What is the situation in which abstract classes become NECESSARY?can anyone brief it with an example?

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  • how to generate abstract for a video?

    - by George2
    Hello everyone, For a video file (e.g. wmv file or other format), I need to generate abstract for the video. The abstract is expected to be in text format. Any mature tools or algorithms? Better (not a must) if open source tools/SDKs so that I can modify for my special needs. thanks in advance, George

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  • Help with abstract class in Java with private variable of type List<E>

    - by Nazgulled
    Hi, It's been two years since I last coded something in Java so my coding skills are bit rusty. I need to save data (an user profile) in different data structures, ArrayList and LinkedList, and they both come from List. I want to avoid code duplication where I can and I also want to follow good Java practices. For that, I'm trying to create an abstract class where the private variables will be of type List<E> and then create 2 sub-classes depending on the type of variable. Thing is, I don't know if I'm doing this correctly, you can take a look at my code: Class: DBList import java.util.List; public abstract class DBList { private List<UserProfile> listName; private List<UserProfile> listSSN; public List<UserProfile> getListName() { return this.listName; } public List<UserProfile> getListSSN() { return this.listSSN; } public void setListName(List<UserProfile> listName) { this.listName = listName; } public void setListSSN(List<UserProfile> listSSN) { this.listSSN = listSSN; } } Class: DBListArray import java.util.ArrayList; public class DBListArray extends DBList { public DBListArray() { super.setListName(new ArrayList<UserProfile>()); super.setListSSN(new ArrayList<UserProfile>()); } public DBListArray(ArrayList<UserProfile> listName, ArrayList<UserProfile> listSSN) { super.setListName(listName); super.setListSSN(listSSN); } public DBListArray(DBListArray dbListArray) { super.setListName(dbListArray.getListName()); super.setListSSN(dbListArray.getListSSN()); } } Class: DBListLinked import java.util.LinkedList; public class DBListLinked extends DBList { public DBListLinked() { super.setListName(new LinkedList<UserProfile>()); super.setListSSN(new LinkedList<UserProfile>()); } public DBListLinked(LinkedList<UserProfile> listName, LinkedList<UserProfile> listSSN) { super.setListName(listName); super.setListSSN(listSSN); } public DBListLinked(DBListLinked dbListLinked) { super.setListName(dbListLinked.getListName()); super.setListSSN(dbListLinked.getListSSN()); } } 1) Does any of this make any sense? What am I doing wrong? Do you have any recommendations? 2) It would make more sense for me to have the constructors in DBList and calling them (with super()) in the subclasses but I can't do that because I can't initialize a variable with new List<E>(). 3) I was thought to do deep copies whenever possible and for that I always override the clone() method of my classes and code it accordingly. But those classes never had any lists, sets or maps on them, they only had strings, ints, floats. How do I do deep copies in this situation?

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  • How to persist a very abstract data type between sessions: PHP

    - by Greelmo
    I have an abstract data type that behaves much like stack. It represents a history of "graph objects" made by a particular user. Each "graph object" holds one or more "lines", a date range, keys, and a title. Each "line" holds a sql generator configured for a particular subset of data in my db. I would like for these "histories" to be available to users between their sessions. It will be in the form of a tab that reads something like "most recent graphs". What do you believe to be the best way to persist this type of data between sessions. This application could get rather large, so efficiency is a concern. Thanks in advance.

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  • C# UserControl factory

    - by user1112111
    Let's say you have two classes that extend UserControl. Each of the controls provides a custom event (this could be done by using an interface). You want to display one of the controls in the odd days and the other in the even days. You also want to be able to drag&drop (Visual Studio) the UserControl on your form without knowing what the Control type will finally be. How do you do that ? Is the factory pattern useful here ?

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  • Iphone -- init method of an abstract class

    - by William Jockusch
    I want to create classes Car, Vehicle, and Airplane with the following properties: Car and Airplane are both subclasses of Vehicle. Car and Airplane both have an initWithString method. The acceptable input strings for Car's and Airplane's initWithString methods do not overlap. Vehicle is "almost abstract", in the sense that any initialized instance should be either a Car or an Airplane. It is possible to pass a string into Vehicle and get back an instance of Car, an instance of Airplane, or nil, depending on the input string. Any particular design pattern I should prefer? In particular for Vehicle's initWithString and/or newVehicleWithString methods.

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  • Recommended way to remove events on destroy with jQuery UI Widget Factory

    - by user1031947
    I'm using the jQuery UI Widget Factory to build a jQuery plugin. My plugin binds custom events to the window... _subscribe: function() { $(window).on("dragger.started", function() { ... }); } I am wondering how to go about removing these events, when a particular instance of the plugin is destroyed. If I use... destroy: function() { $(window).off("dragger.started"); } ...then that will mess up any other instances of the plugin on the page, as it will remove all "dragger.started" events. What is the recommended way to go about destroying only those events that are associated with an instance of the plugin? Thanks (in advance) for your help.

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  • Determine an object's class returned by a factory method (Error: function does not take 1 arguments

    - by tzippy
    I have a factorymethod that either returns an object of baseclass or one that is of derivedclass (a derived class of baseclass). The derived class has a method virtual void foo(int x) that takes one argument. baseclass however has virtual void foo() without an argument. In my code, a factory method returns a pointer of type bar that definetly points to an object of class derivedclass. However since this is only known at runtime I get a compiler error saying that foo() does not take an argument. Can I cast this pointer to a pointer of type derivedclass? std::auto_ptr<baseclass> bar = classfactory::CreateBar(); //returns object of class derivedclass bar->foo(5); class baseclass { public: virtual void foo(); } class derivedclass : public baseclass { public: virtual void foo(int x); }

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  • Using the Specification Pattern

    - by Kane
    Like any design pattern the Specification Pattern is a great concept but susceptible to overuse by an eager architect/developer. I am about to commence development on a new application (.NET & C#) and really like the concept of the Specification Pattern and am keen to make full use of it. However before I go in all guns blazing I would be really interested in knowing if anyone could share the pain points that experienced when use the Specification Pattern in developing an application. Ideally I'm looking to see if others have had issues in Writing unit tests against the specification pattern Deciding which layer the specifications should live in (Repository, Service, Domain, etc) Using it everywhere when a simple if statement would have done the job etc? Thanks in advance

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  • Spring factory beans not always initialised before being used.

    - by aos
    Hi, I am using spring to initialise my beans. I have configured a bean which I intend to use as a factory bean. <bean id="jsServicesFactory" class="x.y.z.JSServicesFactory" /> It is a very basic class - which has 4 getter methods. One example is public final PortletRegistry getPortletRegistry() { PortletRegistry registry = (PortletRegistry) JetspeedPortletServices .getSingleton().getService("PortletRegistryComponent"); return registry; } I have a 2nd bean which uses this factory beans to set one of its properties <bean id="batchManagerService" class="x.y.z.BatchManagerService"> ... <property name="portletRegistry"> <bean factory-bean="jsServicesFactory" factory-method="getPortletRegistry" /> </property> ... When I start my server in RAD, this all works perfectly. However when I deploy to Linux I sometimes get the following error ERROR org.springframework.web.context.ContextLoader - Context initialization failed org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'batchManagerService' defined in ServletContext resource [/WEB-INF/context/root/batchManagerContext.xml]: Cannot create inner bean 'jsServicesFactory$created#70be70be' while setting bean property 'portletRegistry'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jsServicesFactory$created#70be70be' defined in ServletContext resource [/WEB-INF/context/root/batchManagerContext.xml]: Instantiation of bean failed; nested exception is org.springframework.beans.factory.BeanDefinitionStoreException: Factory method [public final org.apache.jetspeed.components.portletregistry.PortletRegistry x.y.z.JSServicesFactory.getPortletRegistry()] threw exception; nested exception is java.lang.NullPointerException I have tried adding depends-on="jsServicesFactory" to my bean batchManagerService but it didn't work. Any ideas? Thanks

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  • Abstract Factory Using Generics: Is Explicitly Converting a Specified Type to Generic a Bad Practice

    - by Merritt
    The question's title says it all. I like how it fits into the rest of my code, but does it smell? public interface IFoo<T> { T Bar { get; set; } } public class StringFoo : IFoo<string> { public string Bar { get; set; } } public static class FooFactory { public static IFoo<T> CreateFoo<T>() { if (typeof(T) == typeof(string)) { return new StringFoo() as IFoo<T>; } throw new NotImplementedException(); } } UPDATE: this is sort of a duplicate of Is the StaticFactory in codecampserver a well known pattern?

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  • Is component-based design an architectural pattern or design pattern?

    - by xEnOn
    When using the component-based paradigm in game development with engines like Unity, is component-based design an architectural pattern, or a design pattern? Can I even say that component-based design is my "main" architectural pattern for my game? I see architectural patterns as being more high-level than design pattern. The component-based design in game development's context (like with Unity engine) seems to fit as an architectural pattern to me. However, on some sites, I read that component-based design is a behavioural pattern, much like other behavioural design patterns, and not so much like an architectural pattern like MVC.

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  • EmguCV: Can't find ColorType abstract class

    - by roverred
    EmguCV ColorType wiki I'm trying to create a ColorType abstract class variable but it says the type or namespace does not exist. However I have access to the classes that extend it. I also tried adding all Emgu.CV libraries and have all the references and .dll files in the bin folder. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Drawing; using Emgu.CV; using Emgu.CV.Util; using Emgu.CV.GPU; using Emgu.CV.ML; using Emgu.CV.OCR; using Emgu.CV.OpenCL; using Emgu.CV.Stitching; using Emgu.CV.VideoStab; using Emgu.CV.Structure; using Emgu.CV.UI; using Emgu.CV.CvEnum; namespace mySpace { class foo { private ColorType the color; //invalid can't find ColorType private ColorType myColor = new Gray(); //invalid } } Any ideas? Thanks for any help.

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  • Cannot create instance of abstract class

    - by SmartestVEGA
    I am trying to compile the following code and i am getting the error: Cannot create instance of abstract class . Please help m_objExcel = new Excel.Application(); m_objBooks = (Excel.Workbooks)m_objExcel.Workbooks; m_objBook = (Excel._Workbook)(m_objBooks.Add(m_objOpt)); m_objSheets = (Excel.Sheets)m_objBook.Worksheets; m_objSheet = (Excel._Worksheet)(m_objSheets.get_Item(1)); // Create an array for the headers and add it to cells A1:C1. object[] objHeaders = {"Order ID", "Amount", "Tax"}; m_objRange = m_objSheet.get_Range("A1", "C1"); m_objRange.Value = objHeaders; m_objFont = m_objRange.Font; m_objFont.Bold=true; // Create an array with 3 columns and 100 rows and add it to // the worksheet starting at cell A2. object[,] objData = new Object[100,3]; Random rdm = new Random((int)DateTime.Now.Ticks); double nOrderAmt, nTax; for(int r=0;r<100;r++) { objData[r,0] = "ORD" + r.ToString("0000"); nOrderAmt = rdm.Next(1000); objData[r,1] = nOrderAmt.ToString("c"); nTax = nOrderAmt*0.07; objData[r,2] = nTax.ToString("c"); } m_objRange = m_objSheet.get_Range("A2", m_objOpt); m_objRange = m_objRange.get_Resize(100,3); m_objRange.Value = objData; // Save the Workbook and quit Excel. m_objBook.SaveAs(m_strSampleFolder + "Book2.xls", m_objOpt, m_objOpt, m_objOpt, m_objOpt, m_objOpt, Excel.XlSaveAsAccessMode.xlNoChange, m_objOpt, m_objOpt, m_objOpt, m_objOpt); m_objBook.Close(false, m_objOpt, m_objOpt); m_objExcel.Quit();

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  • Dependency injection and factory

    - by legenden
    Trying to figure out how to best handle the following scenario: Assume a RequestContext class which has a dependency to an external service, such as: public class RequestContext : IRequestContext { private readonly ServiceFactory<IWeatherService> _weatherService; public RequestContext(ServiceFactory<IWeatherService> weatherService, UserLocation location, string query) { _weatherService = weatherService; ... What sort of dependency should I require in the class that will ultimately instantiate RequestContext? It could be ServiceFactory<IWeatherService>, but that doesn't seem right, or I could create an IRequestContextFactory for it along the lines of: public class RequestContextFactory : IRequestContextFactory { private readonly ServiceFactory<IWeatherService> _weatherService; public RequestContextFactory(ServiceFactory<IWeatherService> weatherService) { _weatherService = weatherService; } public RequestContext Create(UserLocation location, string query) { return new RequestContext(_weatherService, location, query); } } And then pass the IRequestContextFactory through constructor injection. This seems like a good way to do it, but the problem with this approach is that I think it hinders discoverability (devs must know about the factory and implement it, which is not really apparent). Is there a better/more discoverable way that I'm missing?

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  • variables in abstract classes C++

    - by wyatt
    I have an abstract class CommandPath, and a number of derived classes as below: class CommandPath { public: virtual CommandResponse handleCommand(std::string) = 0; virtual CommandResponse execute() = 0; virtual ~CommandPath() {} }; class GetTimeCommandPath : public CommandPath { int stage; public: GetTimeCommandPath() : stage(0) {} CommandResponse handleCommand(std::string); CommandResponse execute(); }; All of the derived classes have the member variable 'stage'. I want to build a function into all of them which manipulates 'stage' in the same way, so rather than defining it many times I thought I'd build it into the parent class. I moved 'stage' from the private sections of all of the derived classes into the protected section of CommandPath, and added the function as follows: class CommandPath { protected: int stage; public: virtual CommandResponse handleCommand(std::string) = 0; virtual CommandResponse execute() = 0; std::string confirmCommand(std::string, int, int, std::string, std::string); virtual ~CommandPath() {} }; class GetTimeCommandPath : public CommandPath { public: GetTimeCommandPath() : stage(0) {} CommandResponse handleCommand(std::string); CommandResponse execute(); }; Now my compiler tells me for the constructor lines that none of the derived classes have a member 'stage'. I was under the impression that protected members are visible to derived classes? The constructor is the same in all classes, so I suppose I could move it to the parent class, but I'm more concerned about finding out why the derived classes aren't able to access the variable. Also, since previously I've only used the parent class for pure virtual functions, I wanted to confirm that this is the way to go about adding a function to be inherited by all derived classes.

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