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Search found 50247 results on 2010 pages for 'base class'.

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  • 7 drived classes with one common base class

    - by user144905
    i have written the following code, //main.cpp #include<iostream> #include<string> #include"human.h" #include"computer.h" #include"referee.h" #include"RandomComputer.h" #include"Avalanche.h" #include"Bureaucrat.h" #include"Toolbox.h" #include"Crescendo.h" #include"PaperDoll.h" #include"FistfullODollors.h" using namespace std; int main() { Avalanche pla1; Avalanche pla2; referee f; pla1.disp(); for (int i=0;i<5;i++) { cout<<pla2.mov[i]; } return 0; } in this program all included classes except referee.h and human.h are drived from computer.h. each drived calls has a char array variable which is initialized when a member of a drived class is declared. the problem is that when i declare tow diffrent drived class memebers lets say Avalache and ToolBox. upon printing the char array for one of them using for loop it prints nothing. However if i declare only one of them in main.cpp the it works properly. and the file for computer.h is as such: #ifndef COMPUTER_H #define COMPUTER_H class computer { public: int nump; char mov[]; void disp(); }; #endif ToolBox.h is like this: #ifndef TOOLBOX_H #define TOOLBOX_H #include"computer.h" class Toolbox: public computer { public: Toolbox(); }; #endif finally Avalanche.h is as following: #ifndef AVALANCHE_H #define AVALANCHE_H #include"computer.h" class Avalanche: public computer { public: Avalanche(); }; #endif

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  • Abstract class + Inheritance vs Interface

    - by RealityDysfunction
    Hello fellow programmers, I am reading a book on C# and the author is comparing Abstract classes and Interfaces. He claims that if you have the following "abstract class:" abstract class CloneableType { public abstract object Clone(); } Then you cannot do this: public class MiniVan : Car, CloneableType {} This, I understand. However he claims that because of this inability to do multiple inheritance that you should use an interface for CloneableType, like so: public interface ICloneable { object Clone(); } My question is, isn't this somewhat misleading, because you can create an abstract class which is "above" class Car with the method Clone, then have Car inherit that class and then Minivan will inherit Car with all these methods, CloneAble class - Car class - Minivan Class. What do you think? Thanks.

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  • Why should I declare a class as an abstract class?

    - by Pied Piper
    I know the syntax, rules applied to abstract class and I want know usage of an abstract class Abstract class can not be instantiated directly but can be extended by other class What is the advantage of doing so? How it is different from an Interface? I know that one class can implement multiple interfaces but can only extend one abstract class. Is that only difference between an interface and an abstract class? I am aware about usage of an Interface. I have learned that from Event delegation model of AWT in Java. In which situations I should declare class as an abstract class? What is benefits of that?

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  • Python: query a class's parent-class after multiple derivations ("super()" does not work)

    - by henry
    Hi, I have built a class-system that uses multiple derivations of a baseclass (object-class1-class2-class3): class class1(object): def __init__(self): print "class1.__init__()" object.__init__(self) class class2(class1): def __init__(self): print "class2.__init__()" class1.__init__(self) class class3(class2): def __init__(self): print "class3.__init__()" class2.__init__(self) x = class3() It works as expected and prints: class3.__init__() class2.__init__() class1.__init__() Now I would like to replace the 3 lines object.__init__(self) ... class1.__init__(self) ... class2.__init__(self) with something like this: currentParentClass().__init__() ... currentParentClass().__init__() ... currentParentClass().__init__() So basically, i want to create a class-system where i don't have to type "classXYZ.doSomething()". As mentioned above, I want to get the "current class's parent-class". Replacing the three lines with: super(type(self), self).__init__() does NOT work (it always returns the parent-class of the current instance - class2) and will result in an endless loop printing: class3.__init__() class2.__init__() class2.__init__() class2.__init__() class2.__init__() ... So is there a function that can give me the current class's parent-class? Thank you for your help! Henry -------------------- Edit: @Lennart ok maybe i got you wrong but at the moment i think i didn't describe the problem clearly enough.So this example might explain it better: lets create another child-class class class4(class3): pass now what happens if we derive an instance from class4? y = class4() i think it clearly executes: super(class3, self).__init__() which we can translate to this: class2.__init__(y) this is definitly not the goal(that would be class3.__init__(y)) Now making lots of parent-class-function-calls - i do not want to re-implement all of my functions with different base-class-names in my super()-calls.

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  • How to use derived class shared variables in shared methods of base class

    - by KoolKabin
    Hi guys, I am trying to add shared members in derived classes and use that values in base classes... I have base class DBLayer public shared function GetDetail(byval UIN as integer) dim StrSql = string.format("select * from {0} where uin = {1}", tablename, uin) .... end function end class my derived class class User inherits dblayer public shared tabledname as string = "users" end class class item inherits dblayer public shared tabledname as string = "item" end class class category inherits dblayer public shared tabledname as string = "category" end class currently there is error using the tablename variable of derived class in base class but i want to use it... coz i dun know other techniques... if other solutions are better then u can post it or u can say how can i make it work? confused...

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  • Advantages of Singleton Class over Static Class?

    Point 1)Singleton We can get the object of singleton and then pass to other methods.Static Class We can not pass static class to other methods as we pass objectsPoint 2) Singleton In future, it is easy to change the logic of of creating objects to some pooling mechanism. Static Class Very difficult to implement some pooling logic in case of static class. We would need to make that class as non-static and then make all the methods non-static methods, So entire your code needs to be changed.Point3:) Singleton Can Singletone class be inherited to subclass? Singleton class does not say any restriction of Inheritence. So we should be able to do this as long as subclass is also inheritence.There's nothing fundamentally wrong with subclassing a class that is intended to be a singleton. There are many reasons you might want to do it. and there are many ways to accomplish it. It depends on language you use.Static Class We can not inherit Static class to another Static class in C#. Think about it this way: you access static members via type name, like this: MyStaticType.MyStaticMember(); Were you to inherit from that class, you would have to access it via the new type name: MyNewType.MyStaticMember(); Thus, the new item bears no relationships to the original when used in code. There would be no way to take advantage of any inheritance relationship for things like polymorphism. span.fullpost {display:none;}

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  • Advantages of Singleton Class over Static Class?

    Point 1) Singleton We can get the object of singleton and then pass to other methods. Static Class We can not pass static class to other methods as we pass objects Point 2) Singleton In future, it is easy to change the logic of of creating objects to some pooling mechanism. Static Class Very difficult to implement some pooling logic in case of static class. We would need to make that class as non-static and then make all the methods non-static methods, So entire your code needs to be changed. Point3:) Singleton Can Singletone class be inherited to subclass? Singleton class does not say any restriction of Inheritence. So we should be able to do this as long as subclass is also inheritence.There's nothing fundamentally wrong with subclassing a class that is intended to be a singleton. There are many reasons you might want to do it. and there are many ways to accomplish it. It depends on language you use. Static Class We can not inherit Static class to another Static class in C#. Think about it this way: you access static members via type name, like this: MyStaticType.MyStaticMember(); Were you to inherit from that class, you would have to access it via the new type name: MyNewType.MyStaticMember(); Thus, the new item bears no relationships to the original when used in code. There would be no way to take advantage of any inheritance relationship for things like polymorphism. span.fullpost {display:none;}

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  • convert integer to a string in a given numeric base in python

    - by Mark Borgerding
    Python allows easy creation of an integer from a string of a given base via int(str,base). I want to perform the inverse: creation of a string from an integer. i.e. I want some function int2base(num,base) such that: int( int2base( X , BASE ) , BASE ) == X the function name/argument order is unimportant For any number X and base BASE that int() will accept. This is an easy function to write -- in fact easier than describing it in this question -- however, I feel like I must be missing something. I know about the functions bin,oct,hex; but I cannot use them for a few reasons: Those functions are not available on older versions of python with which I need compatibility (2.2) I want a general solution that can be called the same way for different bases I want to allow bases other than 2,8,16 Related Python elegant inverse function of int(string,base) Interger to base-x system using recursion in python Base 62 conversion in Python How to convert an integer to the shortest url-safe string in Python?

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  • Visual Studio: Design a UserControl class that derives from an abstract base class

    - by Marcel
    Hi All, I want to have an abstract base class for some of my custom UserControl's. The reason is obvious: they share some common properties and methods (a basic implementation of some elements of an interface actually), and I want to implement them only once. I have done this by defining my abstract base class: public abstract class ViewBase : UserControl, ISomeInterface Then I went to implement one of my views, as usual, with the designer: public partial class SpecialView : UserControl //all OK Up to here all is fine. Now I replace the derivation of my SpecialView class with the abstract base class: public partial class SpecialView : ViewBase //disrupts the designer Now, the designer in Visual Studio 2008 won't work anymore, stating: The designer must create an instance of type 'ViewBase' but it cannot because the type is declared as abstract. How can I circumvent this? I just do not want to have the same code copied for all those views. Info: there is a question question with virtual methods, instead of abstract classes, but there is no suitable solution for me.

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  • Manager/Container class vs static class methods

    - by Ben
    Suppose I a have a Widget class that is part of a framework used independently by many applications. I create Widget instances in many situations and their lifetimes vary. In addition to Widget's instance specified methods, I would like to be able to perform the follow class wide operations: Find a single Widget instance based on a unique id Iterate over the list of all Widgets Remove a widget from the set of all widgets In order support these operations, I have been considering two approaches: Container class - Create some container or manager class, WidgetContainer, which holds a list of all Widget instances, support iteration and provides methods for Widget addition, removal and lookup. For example in C#: public class WidgetContainer : IEnumerable<Widget { public void AddWidget(Widget); public Widget GetWidget(WidgetId id); public void RemoveWidget(WidgetId id); } Static class methods - Add static class methods to Widget. For example: public class Widget { public Widget(WidgetId id); public static Widget GetWidget(WidgetId id); public static void RemoveWidget(WidgetId id); public static IEnumerable<Widget AllWidgets(); } Using a container class has the added problem of how to access the container class. Make it a singleton?..yuck! Create some World object that provides access to all such container classes? I have seen many frameworks that use the container class approach, so what is the general consensus?

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  • class inheretence of a attribute which is itself a class

    - by alex
    i have a class which inherets a attribute from a super-class. this attribute is a class itself. class classA(superClass): def func(self,x): if self.attributeB is None: do somthing and in the other class i have class superClass: self.attributB = classB() i get the error AttributeError: class classA has no attribute 'attributeB' when i access the attribute like i showed but if on command line i can see it works, x = classA() x.attributeB is None True so the test works. whats going on in the above code?

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  • Top Tips and Tricks Documents for Oracle Install Base

    - by Oracle_EBS
     EBS Install Base Implementer?  Consider the following references as identified by Oracle Install Base Engineers as our Top Tips and Tricks knowledge documents. Top Install Base Tips and Tricks Documents Troubleshoot: Oracle Install Base (Doc ID 1351860.1) How to Use Installed Base Error Transaction Diagnostics Script IBtxnerr.sql (Doc ID 365697.1) Cannot See Customer Product Instance in Installed Base after Item is Shipped (Doc ID 1309943.1) How To Obtain the CSE/CSI Log and Debug Files For Your Oracle Support Engineer (Doc ID 239627.1) Troubleshooting Install Base Errors in the Transaction Errors Processing Form (Doc ID 577978.1) How to Solve Installed Base Error Transactions Using Installed Base Data Correction and Synchronization Program (Doc ID 734933.1) Common Installed Base Transaction Error Messages (Doc ID 856825.1) Install Base Transaction Errors Master Repository (Doc ID 1289858.1) How To Remove Extended Attributes From IB? (Doc ID 1357667.1) 

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  • Using a database class in my user class

    - by Josh
    In my project I have a database class that I use to handle all the MySQL stuff. It connects to a database, runs queries, catches errors and closes the connection. Now I need to create a members area on my site, and I was going to build a users class that would handle registration, logging in, password/username changes/resets and logging out. In this users class I need to use MySQL for obvious reasons... which is what my database class was made for. But I'm confused as to how I would use my database class in my users class. Would I want to create a new database object for my user class and then have it close whenever a method in that class is finished? Or do I somehow make a 'global' database class that can be used throughout my entire script (if this is the case I need help with that, no idea what to do there.) Thanks for any feedback you can give me.

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  • Using a datanase class in my user class?

    - by Josh
    In my project I have a database class that I use to handle all the MySQL stuff. It connects to a database, runs queries, catches errors and closes the connection. Now I need to create a members area on my site, and I was going to build a users class that would handle registration, logging in, password/username changes/resets and logging out. In this users class I need to use MySQL for obvious reasons... which is what my database class was made for. But I'm confused as to how I would use my database class in my users class. Would I want to create a new database object for my user class and then have it close whenever a method in that class is finished? Or do I somehow make a 'global' database class that can be used throughout my entire script (if this is the case I need help with that, no idea what to do there.) Thanks for any feedback you can give me.

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  • Why do pure virtual base classes get direct access to static data members while derived instances do

    - by Shamster
    I've created a simple pair of classes. One is pure virtual with a static data member, and the other is derived from the base, as follows: #include <iostream> template <class T> class Base { public: Base (const T _member) { member = _member; } static T member; virtual void Print () const = 0; }; template <class T> T Base<T>::member; template <class T> void Base<T>::Print () const { std::cout << "Base: " << member << std::endl; } template <class T> class Derived : public Base<T> { public: Derived (const T _member) : Base<T>(_member) { } virtual void Print () const { std::cout << "Derived: " << this->member << std::endl; } }; I've found from this relationship that when I need access to the static data member in the base class, I can call it with direct access as if it were a regular, non-static class member. i.e. - the Base::Print() method does not require a this- modifier. However, the derived class does require the this-member indirect access syntax. I don't understand why this is. Both class methods are accessing the same static data, so why does the derived class need further specification? A simple call to test it is: int main () { Derived<double> dd (7.0); dd.Print(); return 0; } which prints the expected "Derived: 7"

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  • Can i access outer class objects in inner class

    - by Shantanu Gupta
    I have three classes like this. class A { public class innerB { //Do something } public class innerC { //trying to access objB here directly or indirectly over here. //I dont have to create an object of innerB, but to access the object created by A //i.e. innerB objInnerB = objB; //not like this innerB objInnerB= new innerB(); } public innerB objB{get;set;} } I want to access the object of class B in Class C that is created by class A. Is it possible somehow to make changes on object of Class A in Class C. Can i get Class A's object by creating event or anyhow.

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  • Linking a template class using another template class (error LNK2001)

    - by Luís Guilherme
    I implemented the "Strategy" design pattern using an Abstract template class, and two subclasses. Goes like this: template <class T> class Neighbourhood { public: virtual void alter(std::vector<T>& array, int i1, int i2) = 0; }; and template <class T> class Swap : public Neighbourhood<T> { public: virtual void alter(std::vector<T>& array, int i1, int i2); }; There's another subclass, just like this one, and alter is implemented in the cpp file. Ok, fine! Now I declare another method, in another class (including neighbourhood header file, of course), like this: void lSearch(/*parameters*/, Neighbourhood<LotSolutionInformation> nhood); It compiles fine and cleanly. When starting to link, I get the following error: 1>SolverFV.obj : error LNK2001: unresolved external symbol "public: virtual void __thiscall lsc::Neighbourhood<class LotSolutionInformation>::alter(class std::vector<class LotSolutionInformation,class std::allocator<class LotSolutionInformation> > &,int,int)" (?alter@?$Neighbourhood@VLotSolutionInformation@@@lsc@@UAEXAAV?$vector@VLotSolutionInformation@@V?$allocator@VLotSolutionInformation@@@std@@@std@@HH@Z)

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  • Building a database class in PHP

    - by Sprottenwels
    I wonder if I should write a database class for my application, and if so, how to accomplish it? Over there on SO, a guy mentioned it should be written as an abstract class. However, I can't understand why this would be a benefit. Do I understand correctly, that if I would write an abstract class, every other class that methods will need a database connection, could simply extend this abstract class and have it's own database object? If so, how is this different from a "normal" class where I could instantiate an database object? Another method would be to completely forget about my own class and to instantiate a mysqli object on demand. What do you recommend?

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  • Class design for calling "the same method" on different classes from one place

    - by betatester07
    Let me introduce my situation: I have Java EE application and in one package, I want to have classes which will act primarily as cache for some data from database, for example: class that will hold all articles for our website class that will hold all categories etc. Every class should have some update() method, which will update data for that class from database and also some other methods for data manipulation specific for that data type. Now, I would like to call update() method for all class instances (there will be exactly one class instance for every class) from one place. What is the best design?

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  • Using a class within a class?

    - by Josh
    I built myself a MySQL class which I use in all my projects. I'm about to start a project that is heavily based on user accounts and I plan on building my own class for this aswell. The thing is, a lot of the methods in the user class will be MySQL queries and methods from the MySQL class. For example, I have a method in my user class to update someone's password: class user() { function updatePassword($usrName, $newPass) { $con = mysql_connect('db_host', 'db_user', 'db_pass'); $sql = "UPDATE users SET password = '$newPass' WHERE username = '$userName'"; $res = mysql_query($sql, $con); if($res) return true; mysql_close($con); } } (I kind of rushed this so excuse any syntax errors :) ) As you can see that would use MySQL to update a users password, but without using my MySQL class, is this correct? I see no way in which I can use my MySQL class within my users class without it seeming dirty. Do I just use it the normal way like $DB = new DB();? That would mean including my mysql.class.php somewhere too... I'm quite confused about this, so any help would be appreciated, thanks.

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  • Identifying that a variable is a new-style class in Python?

    - by Dave Johansen
    I'm using Python 2.x and I'm wondering if there's a way to tell if a variable is a new-style class? I know that if it's an old-style class that I can do the following to find out. import types class oldclass: pass def test(): o = oldclass() if type(o) is types.InstanceType: print 'Is old-style' else: print 'Is NOT old-style' But I haven't been able to find anything that works for new-style classes. I found this question, but the proposed solutions don't seem to work as expected, because simple values as are identified as classes. import inspect def newclass(object): pass def test(): n = newclass() if inspect.isclass(n): print 'Is class' else: print 'Is NOT class' if inspect.isclass(type(n)): print 'Is class' else: print 'Is NOT class' if inspect.isclass(type(1)): print 'Is class' else: print 'Is NOT class' if isinstance(n, object): print 'Is class' else: print 'Is NOT class' if isinstance(1, object): print 'Is class' else: print 'Is NOT class' So is there anyway to do something like this? Or is everything in Python just a class and there's no way to get around that?

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  • How to get a Class literal from a generically specific Class

    - by h2g2java
    There are methods like these which require Class literals as argument. Collection<EmpInfo> emps = SomeSqlUtil.select( EmpInfo.class, "select * from emps"); or GWT.create(Razmataz.class); The problem presents itself when I need to supply generic specific classes like EmpInfo<String> Razmataz<Integer> The following would be wrong syntax Collection<EmpInfo<String>> emps = SomeSqlUtil.select( EmpInfo<String>.class, "select * from emps"); or GWT.create(Razmataz<Integer>.class); Because you cannot do syntax like Razmataz<Integer>.class So, how would I be able to squeeze a class literal out of EmpInfo<String> Razmataz<Integer> so that I could feed them as arguments to methods requiring Class literals? Further info Okay, I confess that I am asking this primarily for GWT. I have a pair of GWT RPC interface Razmataz. (FYI, GWT RPC interface has to be defined in server-client pairs). I plan to use the same interface pair for communicating whether it be String, Integer, Boolean, etc. GWT.create(Razmataz) for Razmataz<T> complains that, since I did not specify T, GWT compiler treated it as Object. Then GWT compiler would not accept Object class. It needs to be more specific than being an Object. So, it seems there is no way for me to tell GWT.create what T is because a Class literal is a runtime concept while generics is a compile time concept, Right?

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  • Getting the class of an n dimensional array of an runtime supplied class name

    - by MeBigFatGuy
    Given a fully qualified class name, and a number of dimensions, i would like to get the Class name for this class. I believe i can do this like such public Class<?> getArrayClass(String className, int dimensions) throws ClassNotFoundException { Class<?> elementType = Class.forName(className); return Array.newInstance(elementType, new int[dimensions]).getClass(); } However this requires me to create an unneeded instance of the class. Is there a way to do this without creating the instance? It does not appear that Class.forName("[[[[Ljava/lang/String;") (or a algorithmically generated version) works correctly in all instances from various blog posts i've seen.

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  • Returning and instance of a Class given its .class (MyClass.class)

    - by jax
    I have an enum that will hold my algorithms. I cannot instantiate these classes because I need the application context which is only available once the application has started. I want to load the class at runtime when I choose by calling getAlgorithm(Context cnx). How do I easily instantiate a class at runtime given its .class (and my constructor takes arguments)? All my classes are subclasses of Algorithm. public enum AlgorithmTypes { ALL_FROM_9_AND_LAST_FROM_10_ID(AlgorithmFactory.AlgorithmAllFrom9AndLastFrom10Impl.class), ALL_FROM_9_AND_LAST_FROM_10_CURRENCY_ID(AlgorithmFactory.AlgorithmAllFrom9AndLastFrom10Impl.class), DIVIDE_BY_9_LESS_THAN_100(AlgorithmFactory.AlgorithmAllFrom9AndLastFrom10Impl.class), TABLES_BEYOND_5_BY_5(AlgorithmFactory.AlgorithmAllFrom9AndLastFrom10Impl.class); private Class<? extends Algorithm> algorithm; AlgorithmTypes(Class<? extends Algorithm> c) { algorithm = c; } public Algorithm getAlgorithm(Context cnx) { return //needs to return the current algoriths constructor which takes the Context Algorithm(Context cnx); } }

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