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  • accessing base class's method with derived class's object which has a method of same name.

    - by ashish yadav
    when accessing foo() of "base" using derived class's object. include class base { public: void foo() { std::cout<<"\nHello from foo\n"; } }; class derived : public base { public: void foo(int k) { std::cout<<"\nHello from foo with value = "< } how to access base class method having a method of same name in derived class. the error generated has been shown. i apologize if i am not clear but i feel i have made myself clear as water. thanks in advance.

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  • How to inherit events between objects

    - by marduck19
    I need inherit events and properties for example move a picture around the form Y have this code to move the picture but y need create multiple images with the same behavior private void pictureBox_MouseDown(object sender, MouseEventArgs e) { if (e.Button == MouseButtons.Left) { x = e.X; y = e.Y; } } private void pictureBox_MouseMove(object sender, MouseEventArgs e) { if (e.Button == MouseButtons.Left) { pictureBox.Left += (e.X -x); pictureBox.Top += (e.Y - y); } }

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  • C# Hiding, overriding and calling function from base class.

    - by Lukasz Lysik
    I'm learning C# and I encountered the following problem. I have two classes: base and derived: class MyBase { public void MyMethod() { Console.WriteLine("MyBase::MyMethod()"); } } class MyDerived: MyBase { public void MyMethod() { Console.WriteLine("MyDerived::MyMethod()"); } } For now, without virtual and override key words. When I compile this I get the warning (which is of course expected) that I try to hide MyMethod from MyBase class. What I want to do is to call the method from the base class having an instance of derived class. I do this like this: MyDerived myDerived = new MyDerived(); ((MyBase)myDerived).MyMethod(); It works fine when I do not specify any virtual, etc. keywords in the methods. I tried to put combination of the keywords and I got the following results: | MyBase::MyMethod | MyDerived::MyMethod | Result printed on the console | | -----------------|---------------------|-------------------------------| | - | - | MyBase::MyMethod() | | - | new | MyBase::MyMethod() | | virtual | new | MyBase::MyMethod() | | virtual | override | MyDerived::MyMethod() | I hope the table is clear to you. I have two questions: Is it the correct way to call the function from the base class (((MyBase)myDerived).MyMethod();)? I know about base keyword, but it can be called only from the inside of the derived class. Is it right? Why in the last case (with virtual and override modifiers) the method which was called came from the derived class? Would you please explain that?

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  • Calling Subclass Method in Java

    - by destructo_gold
    Given the following situation (UML below), If Y has the method: public void PrintWs(); and X has: ArrayList <P> myPs = new ArrayList(); Y y = new Y(); Z z = new Z(); myPs.add(y); myPs.add(z); How do I loop through each myPs object and call all Ys PrintWs (without using instanceof)? http://starbucks.mirror.waffleimages.com/files/68/68c26b815e913acd00307bf27bde534c0f1f8bfb.jpg

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  • Returning a C++ reference in a const member functionasses

    - by Chris Kaminski
    A have a class hierarchy that looks somethign like this: class AbstractDataType { public: virtual int getInfo() = 0; }; class DataType: public AbstractDataType { public: virtual int getInfo() { }; } class Accessor { DataType data; public: const AbstractDataType& getData() const { return(data); } } Well, GCC 4.4 reports: In member function ‘const AbstractDataType& Accessor::getData() const’: error: invalid initialization of reference of type ‘const AbstractDataType&’ from expression of type ‘const DataType’ Where am I going wrong - is this a case where I MUST use a pointer?

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  • Python: how to inherite and override

    - by Guy
    Consider this situation: I get an object of type A which has the function f. I.e: class A: def f(): print 'in f' def h(): print 'in h' and I get an instance of this class but I want to override the f function but save the rest of the functionality of A. So what I was thinking was something of the sort: class B(A): .... def f(): print 'in B->f' and the usage would be: def main(a): b = B(a) b.f() #prints "in B->f" b.h() #print "in h" How do you do such a thing?

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  • Access static class variable of parent class in Python

    - by fuenfundachtzig
    I have someting like this class A: __a = 0 def __init__(self): A.__a = A.__a + 1 def a(self): return A.__a class B(A): def __init__(self): # how can I access / modify A.__a here? A.__a = A.__a + 1 # does not work def a(self): return A.__a Can I access the __astatic variable in B? It's possible writing a instead of __a, is this the only way? (I guess the answer might be rather short: yes :)

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  • method __getattr__ is not inherited from parent class

    - by ??????
    Trying to subclass mechanize.Browser class: from mechanize import Browser class LLManager(Browser, object): IS_AUTHORIZED = False def __init__(self, login = "", passw = "", *args, **kwargs): super(LLManager, self).__init__(*args, **kwargs) self.set_handle_robots(False) But when I make something like this: lm["Widget[LinksList]_link_1_title"] = anc then I get an error: Traceback (most recent call last): File "<pyshell#8>", line 1, in <module> lm["Widget[LinksList]_link_1_title"] = anc TypeError: 'LLManager' object does not support item assignment Browser class have overridden method __getattr__ as shown: def __getattr__(self, name): # pass through _form.HTMLForm methods and attributes form = self.__dict__.get("form") if form is None: raise AttributeError( "%s instance has no attribute %s (perhaps you forgot to " ".select_form()?)" % (self.__class__, name)) return getattr(form, name) Why my class or instance don't get this method as in parent class?

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  • Qt - invalid conversion to child class

    - by David Davidson
    I'm drawing polygons using the Graphics View framework. I added a polygon to the scene with this: QGraphicsPolygonItem *poly = scene->addPolygon(QPolygonF(vector_of_QPointF)); poly->setPos(some_point); But I need to implement some custom behaviour like selection, mouse over indicator, and other similar stuff on the graphics item. So I declared a class that inherits QGraphicsPolygonItem: #include <QGraphicsPolygonItem> class GridHex : public QGraphicsPolygonItem { public: GridHex(QGraphicsItem* parent = 0); }; GridHex::GridHex(QGraphicsItem* parent) : QGraphicsPolygonItem(parent) { } Not doing much with that class so far, as you can see. But shouldn't replacing QGraphicsPolygonItem with my GridHex class? This is throwing a " invalid conversion from 'QGraphicsPolygonItem*' to 'GridHex*' " error: GridHex* poly = scene->addPolygon(QPolygonF(vector_of_QPointF)); What am I doing wrong?

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  • Why can I not add a set accessor to an overriden property?

    - by Svish
    In a base class I have this property: public virtual string Text { get { return text; } } I want to override that and return a different text, but I would also like to be able to set the text, so I did this: public override string Text { get { return differentText; } set { differentText = value; } } This however does not work. I get a red squiggly under set saying that I can not override because it does not have a set accessor. Why is this aproblem? What should I do?

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  • Interface and base class mix, the right way to implement this

    - by Lerxst
    I have some user controls which I want to specify properties and methods for. They inherit from a base class, because they all have properties such as "Foo" and "Bar", and the reason I used a base class is so that I dont have to manually implement all of these properties in each derived class. However, I want to have a method that is only in the derived classes, not in the base class, as the base class doesn't know how to "do" the method, so I am thinking of using an interface for this. If i put it in the base class, I have to define some body to return a value (which would be invalid), and always make sure that the overriding method is not calling the base. method Is the right way to go about this to use both the base class and an interface to expose the method? It seems very round-about, but every way i think about doing it seems wrong... Let me know if the question is not clear, it's probably a dumb question but I want to do this right.

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  • Ruby get inheriting class

    - by Brian D.
    I'm working on creating my first plugin for rails. I'm still pretty new to ruby and I was wondering if its possible to get the inheriting class? For example, I'm trying to create a plugin that will allow unit testing and functional testing when you are not using migrations. What I'm trying to do is initialize a class variable named controller to be initialized to the type of controller that is being tested. If I have a base class ControllerTest: class ControllerTest < Test::Unit::TestCase attr_accessor :controller def initialize super @controller = "call function that will find the inheriting classes name and create an instance of that controller type." end end So what I'm currently stuck on is getting the name of the inheriting class. Is this possible? And if not, does anyone know another way on how I could go about implementing this? Thanks in advance.

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  • Maven: trying to get my submodule's poms to NOT inherit a plugin in the parent

    - by jobrahms
    My project has a parent pom and several submodule poms. I've put a plugin in the parent that is responsible for building our installer distributables (using install4j). It doesn't make sense to have this plugin run on the submodules, so I've put false in the plugin's config, as seen below. The problem is, when I run mvn clean install install4j:compile it cleans, compiles, and runs the install4j plugin on the parent, but then it tries to run it on the child modules and crashes. Here's the plugin config <plugin> <groupId>com.google.code.maven-install4j</groupId> <artifactId>maven-install4j-plugin</artifactId> <version>0.1.1</version> <inherited>false</inherited> <configuration> <executable>${devenv.install4jc}</executable> <configFile>${basedir}/newinstaller/ehd-demo.install4j</configFile> <releaseId>${project.version}</releaseId> <attach>false</attach> <skipOnMissingExecutable>true</skipOnMissingExecutable> </configuration> </plugin> Am I misunderstanding the purpose of inherited=false? What is the correct way to get this to work? I'm using maven 2.2.0.

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  • With this generics code why am I getting "Argument 1: cannot convert from 'ToplogyLibrary.Relationsh

    - by Greg
    Hi, Any see why I'm getting a "Argument 1: cannot convert from 'ToplogyLibrary.RelationshipBase' to 'TRelationship'" in the code below, in CreateRelationship() ? public class TopologyBase<TKey, TNode, TRelationship> where TNode : NodeBase<TKey>, new() where TRelationship : RelationshipBase<TKey>, new() { // Properties public Dictionary<TKey, TNode> Nodes { get; private set; } public List<TRelationship> Relationships { get; private set; } // Constructors protected TopologyBase() { Nodes = new Dictionary<TKey, TNode>(); Relationships = new List<TRelationship>(); } // Methods public TNode CreateNode(TKey key) { var node = new TNode {Key = key}; Nodes.Add(node.Key, node); return node; } public void CreateRelationship(TNode parent, TNode child) { // Validation if (!Nodes.ContainsKey(parent.Key) || !Nodes.ContainsKey(child.Key)) { throw new ApplicationException("Can not create relationship as either parent or child was not in the graph: Parent:" + parent.Key + ", Child:" + child.Key); } // Add Relationship var r = new RelationshipBase<TNode>(); r.Parent = parent; r.Child = child; Relationships.Add(r); // *** HERE *** "Argument 1: cannot convert from 'ToplogyLibrary.RelationshipBase<TNode>' to 'TRelationship'" } } public class RelationshipBase<TNode> { public TNode Parent { get; set; } public TNode Child { get; set; } } public class NodeBase<T> { public T Key { get; set; } public NodeBase() { } public NodeBase(T key) { Key = key; } }

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  • wcf class implementing multiple service contracts

    - by Archie
    Hello, I have a class TestService which implements two service contracts called IService1 and IService2. But I'm facing a difficulty in implementation. My Code looks as follows: Uri baseAddress = new Uri("http://localhost:8000/ServiceModel/Service"); Uri baseAddress1 = new Uri("http://localhost:8080/ServiceModel/Service1"); ServiceHost selfHost = new ServiceHost(typeof(TestService)); selfHost.AddServiceEndpoint(typeof(IService1), new WSHttpBinding(), baseAddress); selfHost.AddServiceEndpoint(typeof(IService2), new WSHttpBinding(), baseAddress1); ServiceMetadataBehavior smb = new ServiceMetadataBehavior(); smb.HttpGetEnabled = true; selfHost.Description.Behaviors.Add(smb); selfHost.Open(); Console.WriteLine("The service is ready."); Console.WriteLine("Press <ENTER> to terminate service."); Console.WriteLine(); Console.ReadLine(); selfHost.Close(); I'm getting a run time error as: The HttpGetEnabled property of ServiceMetadataBehavior is set to true and the HttpGetUrl property is a relative address, but there is no http base address. Either supply an http base address or set HttpGetUrl to an absolute address. What shall i do about it? Do I realy need two separate endpoints? Thanks.

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  • Convert Subclass to Inherited Class

    - by Dave
    I have a C# .NET 2.0 project A that has a form (TreeForm) that uses Tree objects. I have a project B that has a class Oak that inherits Tree. When I try to reference and use the TreeForm in project B with my Oak objects, it's looking for objects of type Tree. I've tried casting the Oak objects to Tree, but I get the error "Cannot convert type Oak to Tree". How can I use my Oak objects in the TreeForm from project A?

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  • How can I extend PHP DOMElement?

    - by Michael Tsang
    a.php #!/usr/bin/php <?php class HtmlTable extends DOMElement { public function __construct($height, $width) { parent::__construct("table"); for ($i = 0; $i < $height; ++$i) { $row = $this->appendChild(new DOMElement("tr")); for($j = 0; $j < $width; ++$j) { $row->appendChild(new DOMElement("td")); } } } } $document = new DOMDocument("1.0", "UTF-8"); $document->registerNodeClass("DOMElement", "HtmlTable"); $document->appendChild(new HtmlTable(3, 2)); $document->saveXML(); Running it gets Fatal error: Uncaught exception 'DOMException' with message 'No Modification Allowed Error' in /home/www/a.php:9 Stack trace: #0 /home/www/a.php(9): DOMNode->appendChild(Object(DOMElement)) #1 /home/www/a.php(19): HtmlTable->__construct(3, 2) #2 {main} thrown in /home/www/a.php on line 9

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  • Placement of a call to the parent method

    - by Alejandro
    I have a class that has a method. That class has a child class that overrides that method. The child's method has to call the parent's method. In all OO that I've seen or written calls to the parent's version of the same method were on the first line of the method. On a project that I am working on circumstances call for placing that method call at the end of a method. Should I be worried? Is that a code smell? Is this code inherently bad? class Parent { function work() { // stuff } } class Child { function work() { // do thing 1 // do thing 2 parent::work(); // is this a bad practice? // should I call the parent's work() method before // I do anything in this method? } }

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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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  • XSD: xs:sequence & xs:choice combination for xs:extension elements?

    - by bguiz
    Hi, My question is about defining an XML schema that will validate the following sample XML: <rules> <other>...</other> <bool>...</bool> <other>...</other> <string>...</string> <other>...</other> </rules> The order of the child nodes does not matter. The cardinality of the child nodes is 0..unbounded. All the child elements of the rules node have a common base type, rule, like so: <xs:complexType name="booleanRule"> <xs:complexContent> <xs:extension base="rule"> ... </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="stringFilterRule"> <xs:complexContent> <xs:extension base="filterRule"> ... </xs:extension> </xs:complexContent> </xs:complexType> My current attempt at defining the schema for the rules node is below. However, Can I nest xs:choice within xs:sequence? If, where do I specify the maxOccurs="unbounded" attribute? Is there a better way to do this, such as an xs:sequence which specifies only the base type of its child elements? <xs:element name="rules"> <xs:complexType> <xs:sequence> <xs:choice> <xs:element name="bool" type="booleanRule" /> <xs:element name="string" type="stringRule" /> <xs:element name="other" type="someOtherRule" /> </xs:choice> </xs:sequence> </xs:complexType> </xs:element>

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  • custom TreeNode and SelectNodeChanged

    - by gilloux
    Hello, I'm working on asp.net I've written a custom Treenode (customTreeNode) that I use to populate a treeview the problem comes up when firing the selectnodechanged event this event give me a TreeNode object and not a customTreeNode and I cannot seem to cast it somehow, does sy have a clue ? Thx here is the code I have populate my tree node.ChildNodes.Add ( customTreeNode = new customTreeNode(site) ); customTreeNode public class customTreeNode : TreeNode { public Guid Id { get; set; } private SPWebEntry _dataContext; public SPWebEntry DataContext { get { return _dataContext; } } public customTreeNode(SPWebEntry DataContext) { _dataContext = DataContext; this.Text = _dataContext.Title; this.Id = _dataContext.Id; } } and the event void treeViewSiteCollection_SelectedNodeChanged(object sender, EventArgs e) { treeViewSiteCollection.SelectedNode; } treeViewSiteCollection.SelectedNode is of type TreeNode and I cannot cast it. Thx guys

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  • How to invalidate / refresh a domain instance association?

    - by Kimble
    There is a bug in Grails preventing me from using removeFrom* when the node I'm trying to remove is extending the collection type. Removing the node directly from the association won't update the second level cache. A hasMany B Is there any way to manually invalidate or force a reload on an association cache? Invoking refresh() on the many side didn't do the trick.

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  • How to convert an ORM to its subclass using Hibernate ?

    - by Gaaston
    Hi everybody, For example, I have two classes : Person and Employee (Employee is a subclass of Person). Person : has a lastname and a firstname. Employee : has also a salary. On the client-side, I have a single HTML form where i can fill the person informations (like lastname and firstname). I also have a "switch" between "Person" and "Employee", and if the switch is on Employee I can fill the salary field. On the server-side, Servlets receive informations from the client and use the Hibernate framework to create/update data to/from the database. The mapping i'm using is a single table for persons and employee, with a discriminator. I don't know how to convert a Person in an Employee. I firstly tried to : load the Person p from the database create an empty Employee e object copy values from p into e set the salary value save e into the database But i couldn't, as I also copy the ID, and so Hibernate told me they where two instanciated ORM with the same id. And I can't cast a Person into an Employee directly, as Person is Employee's superclass. There seems to be a dirty way : delete the person, and create an employee with the same informations, but I don't really like it.. So I'd appreciate any help on that :) Some precisions : The person class : public class Person { protected int id; protected String firstName; protected String lastName; // usual getters and setters } The employee class : public class Employee extends Person { // string for now protected String salary; // usual getters and setters } And in the servlet : // type is the "switch" if(request.getParameter("type").equals("Employee")) { Employee employee = daoPerson.getEmployee(Integer.valueOf(request.getParameter("ID"))); modifyPerson(employee, request); employee.setSalary(request.getParameter("salary")); daoPerson.save(employee ); } else { Person person = daoPerson.getPerson(Integer.valueOf(request.getParameter("ID"))); modifyPerson(employee, request); daoPerson.save(person); } And finally, the loading (in the dao) : public Contact getPerson(int ID){ Session session = HibernateSessionFactory.getSession(); Person p = (Person) session.load(Person.class, new Integer(ID)); return p; } public Contact getEmployee(int ID){ Session session = HibernateSessionFactory.getSession(); Employee = (Employee) session.load(Employee.class, new Integer(ID)); return p; } With this, i'm getting a ClassCastException when trying to load a Person using getEmployee. XML Hibernate mapping : <class name="domain.Person" table="PERSON" discriminator-value="P"> <id name="id" type="int"> <column name="ID" /> <generator class="native" /> </id> <discriminator column="type" type="character"/> <property name="firstName" type="java.lang.String"> <column name="FIRSTNAME" /> </property> <property name="lastName" type="java.lang.String"> <column name="LASTNAME" /> </property> <subclass name="domain.Employee" discriminator-value="E"> <property name="salary" column="SALARY" type="java.lang.String" /> </subclass> </class> Is it clear enough ? :-/

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  • When do instance variables get initialized and values assigned?

    - by AKh
    When doees the instance variable get initialized? Is it after the constructor block is done or before it? Consider this example: public abstract class Parent { public Parent(){ System.out.println("Parent Constructor"); init(); } public void init(){ System.out.println("parent Init()"); } } public class Child extends Parent { private Integer attribute1; private Integer attribute2 = null; public Child(){ super(); System.out.println("Child Constructor"); } public void init(){ System.out.println("Child init()"); super.init(); attribute1 = new Integer(100); attribute2 = new Integer(200); } public void print(){ System.out.println("attribute 1 : " +attribute1); System.out.println("attribute 2 : " +attribute2); } } public class Tester { public static void main(String[] args) { Parent c = new Child(); ((Child)c).print(); } } OUTPUT: Parent Constructor Child init() parent Init() Child Constructor attribute 1 : 100 attribute 2 : null When the memory for the atribute 1 & 2 are allocated in the heap ? Curious to know why is attribute 2 is NULL ? Are there any design flaws?

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  • C# Property Access vs Interface Implementation

    - by ehdv
    I'm writing a class to represent a Pivot Collection, the root object recognized by Pivot. A Collection has several attributes, a list of facet categories (each represented by a FacetCategory object) and a list of items (each represented by a PivotItem object). Therefore, an extremely simplified Collection reads: public class Collection { private List<FacetCategory> categories; private List<PivotItem> items; // other attributes } What I'm unsure of is how to properly grant access to those two lists. Because declaration order of both facet categories and items is visible to the user, I can't use sets, but the class also shouldn't allow duplicate categories or items. Furthermore, I'd like to make the Collection object as easy to use as possible. So my choices are: Have Collection implement IList<PivotItem> and have accessor methods for FacetCategory: In this case, one would add an item to Collection foo by writing foo.Add(bar). This works, but since a Collection is equally both kinds of list making it only pass as a list for one type (category or item) seems like a subpar solution. Create nested wrapper classes for List (CategoryList and ItemList). This has the advantage of making a consistent interface but the downside is that these properties would no longer be able to serve as lists (because I need to override the non-virtual Add method I have to implement IList rather than subclass List. Implicit casting wouldn't work because that would return the Add method to its normal behavior. Also, for reasons I can't figure out, IList is missing an AddRange method... public class Collection { private class CategoryList: IList<FacetCategory> { // ... } private readonly CategoryList categories = new CategoryList(); private readonly ItemList items = new ItemList(); public CategoryList FacetCategories { get { return categories; } set { categories.Clear(); categories.AddRange(value); } } public ItemList Items { get { return items; } set { items.Clear(); items.AddRange(value); } } } Finally, the third option is to combine options one and two, so that Collection implements IList<PivotItem> and has a property FacetCategories. Question: Which of these three is most appropriate, and why?

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