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  • C++ LNK2019 error with constructors and destructors in derived classes

    - by BLH
    I have two classes, one inherited from the other. When I compile, I get the following errors: 1Entity.obj : error LNK2019: unresolved external symbol "public: __thiscall Utility::Parsables::Base::Base(void)" (??0Base@Parsables@Utility@@QAE@XZ) referenced in function "public: __thiscall Utility::Parsables::Entity::Entity(void)" (??0Entity@Parsables@Utility@@QAE@XZ) 1Entity.obj : error LNK2019: unresolved external symbol "public: virtual __thiscall Utility::Parsables::Base::~Base(void)" (??1Base@Parsables@Utility@@UAE@XZ) referenced in function "public: virtual __thiscall Utility::Parsables::Entity::~Entity(void)" (??1Entity@Parsables@Utility@@UAE@XZ) 1D:\Programming\Projects\Caffeine\Debug\Caffeine.exe : fatal error LNK1120: 2 unresolved externals I really can't figure out what's going on.. can anyone see what I'm doing wrong? I'm using Visual C++ Express 2008. Here are the files.. "include/Utility/Parsables/Base.hpp" #ifndef CAFFEINE_UTILITY_PARSABLES_BASE_HPP #define CAFFEINE_UTILITY_PARSABLES_BASE_HPP namespace Utility { namespace Parsables { class Base { public: Base( void ); virtual ~Base( void ); }; } } #endif //CAFFEINE_UTILITY_PARSABLES_BASE_HPP "src/Utility/Parsables/Base.cpp" #include "Utility/Parsables/Base.hpp" namespace Utility { namespace Parsables { Base::Base( void ) { } Base::~Base( void ) { } } } "include/Utility/Parsables/Entity.hpp" #ifndef CAFFEINE_UTILITY_PARSABLES_ENTITY_HPP #define CAFFEINE_UTILITY_PARSABLES_ENTITY_HPP #include "Utility/Parsables/Base.hpp" namespace Utility { namespace Parsables { class Entity : public Base { public: Entity( void ); virtual ~Entity( void ); }; } } #endif //CAFFEINE_UTILITY_PARSABLES_ENTITY_HPP "src/Utility/Parsables/Entity.cpp" #include "Utility/Parsables/Entity.hpp" namespace Utility { namespace Parsables { Entity::Entity( void ) { } Entity::~Entity( void ) { } } }

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  • How to design this class hierarchy?

    - by devoured elysium
    I have defined an Event class: Event and all the following classes inherit from Event: AEvent BEvent CEvent DEvent Now, with the info I gather from all these Event classes, I will make a chart. With AEvent and BEvent, I will generate points for that chart, while with CEvent and DEvent I will paint certain regions of the chart. Now, how should I signal this in my class hierarchy? Should I make AEvent and BEvent inherit from PointEvent while CEvent and DEvent inherit from RegionEvent, being that both RegionEvent and PointEvent inherit from Event? Should I add a field with an Enum to Event with 2 values, Point and Region, and each of the child classes set their value to it? Should I use some kind of pattern here? Which one? Thanks.

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  • wcf class implementing two operation contracts in different service contracts with same name

    - by Archie
    Hello, I have declared two service contracts as follows: [ServiceContract] public interface IContract1 { [OperationContract] double Add(int ip); } [ServiceContract] public interface IContract2 { [OperationContract] double Add(double ip); } I have a class which implements these two contracts. I have created two end points for both the contracts. But I'm not able to access the service from client code. It displays a big error when i try to update the service reference as: Metadata contains an error that cannot be resolved.... There was no endpoint listening at ... etc. I know that you can't have two OperationContracts with the same name but is it possible to have two operation contracts in different service contracts with same name but different signature? Thanks.

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  • What's the difference between isPrototypeOf and intanceof in Javascript?

    - by Steffen Heil
    Hi In some of my own older code, I use the following: Object.prototype.instanceOf = function( iface ) { return iface.prototype.isPrototypeOf( this ); }; Then I do (for example) [].instanceOf( Array ) This works, but it seems the following would do the same: [] instanceof Array Now, surly this is only a very simple example. My question therefor is: Is a instanceof b ALWAYS the same as b.prototype.isPrototypeOf(a) ? Regards, Steffen

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  • Implementation question involving implementing an interface

    - by Vivin Paliath
    I'm writing a set of collection classes for different types of Trees. I'm doing this as a learning exercise and I'm also hoping it turns out to be something useful. I really want to do this the right way and so I've been reading Effective Java and I've also been looking at the way Joshua Bloch implemented the collection classes by looking at the source. I seem to have a fair idea of what is being done, but I still have a few things to sort out. I have a Node<T> interface and an AbstractNode<T> class that implements the Node interface. I then created a GenericNode<T> (a node that can have 0 to n children, and that is part of an n-ary tree) class that extends AbstractNode<T> and implements Node<T>. This part was easy. Next, I created a Tree<T> interface and an AbstractTree<T> class that implements the Tree<T> interface. After that, I started writing a GenericTree<T> class that extends AbstractTree<T> and implements Tree<T>. This is where I started having problems. As far as the design is concerned, a GenericTree<T> can only consist of nodes of type GenericTreeNode<T>. This includes the root. In my Tree<T> interface I have: public interface Tree<T> { void setRoot(Node<T> root); Node<T> getRoot(); List<Node<T>> postOrder(); ... rest omitted ... } And, AbstractTree<T> implements this interface: public abstract class AbstractTree<T> implements Tree<T> { protected Node<T> root; protected AbstractTree() { } protected AbstractTree(Node<T> root) { this.root = root; } public void setRoot(Node<T> root) { this.root = root; } public Node<T> getRoot() { return this.root; } ... rest omitted ... } In GenericTree<T>, I can have: public GenericTree(Node<T> root) { super(root); } But what this means is that you can create a generic tree using any subtype of Node<T>. You can also set the root of a tree to any subtype of Node<T>. I want to be able to restrict the type of the node to the type of the tree that it can represent. To fix this, I can do this: public GenericTree(GenericNode<T> root) { super(root); } However, setRoot still accepts a parameter of type Node<T>. Which means a user can still create a tree with the wrong type of root node. How do I enforce this constraint? The only way I can think of doing is either: Do an instanceof which limits the check to runtime. I'm not a huge fan of this. Remove setRoot from the interface and have the base class implement this method. This means that it is not part of the contract and anyone who wants to make a new type of tree needs to remember to implement this method. Is there a better way? The second question I have concerns the return type of postOrder which is List<Node<T>>. This means that if a user is operating on a GenericTree<T> object and calls postOrder, he or she receives a list that consists of Node<T> objects. This means when iterating through (using a foreach construct) they would have perform an explicit cast to GenericNode<T> if they want to use methods that are only defined in that class. I don't like having to place this burden on the user. What are my options in this case? I can only think of removing the method from the interface and have the subclass implement this method making sure that it returns a list of appropriate subtype of Node<T>. However, this once again removes it from the contract and it's anyone who wants to create a new type of tree has to remember to implement this method. Is there a better way?

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  • Inheriting from the web client class

    - by robUK
    Hello, C# 2008 I am not sure how much work there is to inheriting from the web client class. Currently I am using it in my project. And I can't change to anything else. The customer would like to have a timeout after a certain period of time. The web client doesn't have this. So rather than re-invent the wheel, I am thinking of inheriting from the web client and adding this property. Do you think this is a suitable solution? Could it mean more work just to add this. What is the easiest way to go about this? Many thanks,

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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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  • How to have a policy class implement a virtual function?

    - by dehmann
    I'm trying to design a policy-based class, where a certain interface is implemented by the policy itself, so the class derives from the policy, which itself is a template (I got this kind of thinking from Alexandrescu's book): #include <iostream> #include <vector> class TestInterface { public: virtual void test() = 0; }; class TestImpl1 { public: void test() {std::cerr << "Impl1" << std::endl;} }; template<class TestPolicy> class Foo : public TestInterface, TestPolicy { }; Then, in the main() function, I call test() on (potentially) various different objects that all implement the same interface: int main() { std::vector<TestInterface*> foos; foos.push_back(new Foo<TestImpl1>()); foos[0]->test(); delete foos[0]; return 0; } It doesn't compile, though, because the following virtual functions are pure within ‘Foo<TestImpl1>’: virtual void TestInterface::test() I thought TestInterface::test() is implemented because we derive from TestImpl1?

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  • Call the cast operator of template base class within the derived class

    - by yoni
    I have a template class, called Cell, here the definition: template <class T> class OneCell { ..... } I have a cast operator from Cell to T, here virtual operator const T() const { ..... } Now i have derived class, called DCell, here template <class T> class DCell : public Cell<T> { ..... } I need to override the Cell's cast operator (insert a little if), but after I need to call the Cell's cast operator. In other methods it's should be something like virtual operator const T() const { if (...) { return Cell<T>::operator const T; } else throw ... } but i got a compiler error error: argument of type 'const int (Cell::)()const' does not match 'const int' What can I do? Thank you, and sorry about my poor English.

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  • Java: why does extending need an empty constructor?

    - by HH
    I have classes SearchToUser and getFilesToWord. GetFilesToWord must inherit SearchToUser fields. Extending works if an empty construction in SearchToUser-class, otherwise: cannot find symbol symbol : constructor SearchToUser() location: class SearchToUser public class GetFilesToWord extends SearchToUser{ ^ 1 error make: *** [all] Error 1 I cannot understand why the empty constructor is required for extending.

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  • Inherit from Type class of .Net

    - by Miguel Angelo
    Is there any point at all on inheriting from Type class in .Net? i.e. What could be the meaning of doing so? I am asking this because of this text in MSDN documentation: Notes to Inheritors When you inherit from Type, you must override the following members... list of members. MSDN doc for Type: http://msdn.microsoft.com/en-us/library/system.type.aspx ok, that is actually saying that anyone can inherit from Type... but they dont say why would you ever want to do that. Thanks!

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  • inverse relation to multiple inheriting classes in django

    - by Ofri Raviv
    Here are my schematic models: class Law(models.Model): ... class Bill(models.Model): ... # data for a proposed law, or change of an existing law class PrivateBill(Bill): ... # data for a Bill that was initiated by a parliament member class GovernmentBill(Bill): ... # data for a Bill that was initiated by the government It is possible and likely that in the future I (or maybe someone else) would want to add more Bill types. Every Bill should point to a Law (indicating what law this bill is going to change) and my question is: What is the best way to implement this? If I add the ForeignKey(Law) to Bill, I'll have a relation from every Bill to Law, but a Law would only have an inverse relation to Bills (bill_set), and not a different inverse relation to each type of bill. Of course I'll be able to filter each type of bill to get only the ones pointing to a specific Law, but this is something I think I'll need to use often, so I think having privatebill_set, governmentbill_set etc would make the code more readable. Another possible solution is to add the foreign key to each of the inheriting classes (this would give me a privatebill_set, governmentbill_set, futurebill_set), but that seems hairy because I would be relying on future programmers to remember to add that relation. How would you solve this?

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  • PHP syntax for referencing self with late static binding

    - by Chris
    When I learned PHP it was pretty much in procedural form, more recently I've been trying to adapt to the OOP way of doing things. Hoever the tutorials I've been following were produced before PHP 5.3 when late static binding was introduced. What I want to know is how do I reference self when calling a function from a parent class. For example these two methods were written for a User class which is a child of DatabaseObject. Right now they're sitting inside the User class, but, as they're used in other child classes of DatabaseObject I'd like to promote them to be included inside DatabaseObject. public static function find_all() { global $database; $result_set = self::find_by_sql("select * from ".self::$table_name); return $result_set; } and: protected function cleaned_attributes() { global $database; $clean_attributes = array(); foreach($this->attributes() as $key => $value) { $clean_attributes[$key] = $database->escape_value($value); } return $clean_attributes; } So I have three questions: 1) How do I change the self:: reference when I move it to the parent. Is it static:: or something similar? 2) When calling the function from my code do I call it in the same way, as a function of the child class eg User::find_all() or is there a change there also? 3) Is there anything else I need to know before I start chopping bits up?

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  • Can a class inherit from LambdaExpression in .NET? Or is this not recommended?

    - by d.
    Consider the following code (C# 4.0): public class Foo : LambdaExpression { } This throws the following design-time error: Foo does not implement inherited abstract member System.Linq.Expressions.LambdaExpression.Accept(System.Linq.Expressions.Compiler.StackSpiller) There's absolutely no problem with public class Foo : Expression { } but, out of curiosity and for the sake of learning, I've searched in Google System.Linq.Expressions.LambdaExpression.Accept(System.Linq.Expressions.Compiler.StackSpiller) and guess what: zero results returned (when was the last time you saw that?). Needless to say, I haven't found any documentation on this method anywhere else. As I said, one can easily inherit from Expression; on the other hand LambdaExpression, while not marked as sealed (Expression<TDelegate> inherits from it), seems to be designed to prevent inheriting from it. Is this actually the case? Does anyone out there know what this method is about? EDIT (1): More info based on the first answers - If you try to implement Accept, the editor (C# 2010 Express) automatically gives you the following stub: protected override Expression Accept(System.Linq.Expressions.ExpressionVisitor visitor) { return base.Accept(visitor); } But you still get the same error. If you try to use a parameter of type StackSpiller directly, the compiler throws a different error: System.Linq.Expressions.Compiler.StackSpiller is inaccessible due to its protection level. EDIT (2): Based on other answers, inheriting from LambdaExpression is not possible so the question as to whether or not it is recommended becomes irrelevant. I wonder if, in cases like this, the error message should be Foo cannot implement inherited abstract member System.Linq.Expressions.LambdaExpression.Accept(System.Linq.Expressions.Compiler.StackSpiller) because [reasons go here]; the current error message (as some answers prove) seems to tell me that all I need to do is implement Accept (which I can't do).

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  • XSLT: Is there a way to "inherit" canned functionality?

    - by Ian Boyd
    i am once again having to cobble together a bit of XSLT into order to turn generated XML into (rather than simply generating HTML). i'm having huge deja-vu this time again. i'm once again having to solve again basic problems, e.g.: how to convert characters into valid html entity references how to preserve whitespace/carriage returns when converting to html how to convert to HTML as opposed to xhtml how to convert dates from xml format into presentable format how to tear apart strings with substring This is all stuff that i've solved many times before. But every time i come back to XSLT i have to start from scratch, re-inventing the wheel every time. If it were a programming language i would have a library of canned functions and procedures i can call. i would have subroutines to perform the commonly repeated tasks. i would inherit from a base class that already implements the ugly boilerplate stuff. Is there any way in XSLT to grow, expand and improve the ecosystem with canned code?

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  • Why does a function that takes IEnumerable<interface> not accept IEnumerable<class>?

    - by Matt Whitfield
    Say, for instance, I have a class: public class MyFoo : IMyBar { ... } Then, I would want to use the following code: List<MyFoo> classList = new List<MyFoo>(); classList.Add(new MyFoo(1)); classList.Add(new MyFoo(2)); classList.Add(new MyFoo(3)); List<IMyBar> interfaceList = new List<IMyBar>(classList); But this produces the error: `Argument '1': cannot convert from 'IEnumerable<MyFoo>' to 'IEnumerable<IMyBar>' Why is this? Since MyFoo implements IMyBar, one would expect that an IEnumerable of MyFoo could be treated as an IEnumerable of IMyBar. A mundane real-world example being producing a list of cars, and then being told that it wasn't a list of vehicles. It's only a minor annoyance, but if anyone can shed some light on this, I would be much obliged.

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  • Trying to recognize _NSFaultingMutableSet as member of NSSet

    - by Will
    I'm trying to recognize the result of a generic query to a managed object as an NSSet. Currently the class returned is a member of _NSFaultingMutableSet, which is clearly related, but fails the isMemberOf:[NSSet class] and isKindOf:[NSSet class] calls. Given that Cocoa doesn't do a direct implementation of NSSet, it's not surprising that I've got some air in the pipes, but I'm wondering if I'm messing something obvious up or this requires a higher grade of kung-fu than I possess. Code follows: SEL selector = NSSelectorFromString(someString); if(![self respondsToSelector:selector]){ NSLog(@"Error processing item"); return; } id items = [self performSelector:selector]; Class itemsClass = [items class]; if ( [itemsClass isKindOfClass:[NSSet class]]) { // do something }

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  • Adding STI to Existing Table...

    - by keruilin
    I want to add STI to an existing table using a custom type column. Let's call this taste_type whose corresponding model is Fruit. In the Fruit model I have: set_inheritance_column :taste_type In my migration to add STI I have: class AddSTI < ActiveRecord::Migration def self.up add_column :fruits, :taste_type, :string, :limit => 100, :null => false Fruit.reset_column_information Fruit.find_by_id(1).update_attributes({:taste_type => 'Sour'}) end def self.down remove_column :fruits, :taste_type end end When I run the migration, I get the following error: Mysql::Error: Column 'taste_type' cannot be null: ... Any idea what's going? I can get the migration to run if I comment the set_inheritance_column in the Fruit model, then uncomment it after I run the migration. Obviously, I don't want to do this, however.

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  • MSDN: How can I see what inherits/implements a class/interface?

    - by d03boy
    One thing I really, really miss from Javadoc is the ability to see which classes inherit the class you're looking at. So if you are looking at an abstract class (such as List) then you would be able to see all classes that inherit/implement the class/interface you're looking at. Is this available in the MSDN and I'm just missing it or is this really a missing feature?

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  • C# visually subclass datagridview control VS2005

    - by DRapp
    Maybe its something stupid, but I'm having a problem with a subclass of a DataGridView Control in VS2005 C#. I know I can subclass from almost anything by doing public class MyDataGridView : DataGridView {} no problem, and I put in some things / elements I want applicable globally. Now, I take this gridview and put into a custom user control that will contain other controls too. So I have something like created by the visual designer. I grab some buttons, label, and my derived "MyDataGridView" on it. public partial class MyCompoundDGVPlus : UserControl So, now, I can visually draw, move, change all sorts of settings as needed, no problem. Now, I want this "MyCompoundDGVPlus" class as the basis for other classes, of which I will manipulate settings specific, but want all to have the same look / feel, and otherwise similar flow, hence the derivations. I've even set the "modifiers" setting to public, so I SHOULD be able to modify any of the properties of the controls at any derived level. So, now, I create a new subclass of "MyFirstDetailedDGVPlus" derived from "MyCompoundDGVPlus". Ok visually, all the label, button, datagridview appear. However, now I want to specifically define the columns of the datagridview here in this class visually, but its locked. However, the LABEL on the form, I CAN get all the property settings.... What am I missing.

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  • Method interception in PHP 5.*

    - by Rolf
    Hi everybody, I'm implementing a Log system for PHP, and I'm a bit stuck. All the configuration is defined in an XML file, that declares every method to be logged. XML is well parsed and converted into a multidimensionnal array (classname = array of methods). So far, so good. Let's take a simple example: #A.php class A { public function foo($bar) { echo ' // Hello there !'; } public function bar($foo) { echo " $ù$ùmezf$z !"; } } #B.php class B { public function far($boo) { echo $boo; } } Now, let's say I've this configuration file: <interceptor> <methods class="__CLASS_DIR__A.php"> <method name="foo"> <log-level>INFO</log-level> <log-message>Transaction init</log-message> </method> </methods> <methods class="__CLASS_DIR__B.php"> <method name="far"> <log-level>DEBUG</log-level> <log-message>Useless</log-message> </method> </methods> </interceptor> The thing I'd like AT RUNTIME ONLY (once the XML parser has done his job) is: #Logger.php (its definitely NOT a final version) -- generated by the XML parser class Logger { public function __call($name,$args) { $log_level = args[0]; $args = array_slice($args,1); switch($method_name) { case 'foo': case 'far': //case ..... //write in log files break; } //THEN, RELAY THE CALL TO THE INITIAL METHOD } } #"dynamic" A.php class A extends Logger { public function foo($log_level, $bar) { echo ' // Hello there !'; } public function bar($foo) { echo " $ù$ùmezf$z !"; } } #"dynamic" B.php class B extends Logger { public function far($log_level, $boo) { echo $boo; } } The big challenge here is to transform A and B into their "dynamic" versions, once the XML parser has completed its job. The ideal would be to achieve that without modifying the code of A and B at all (I mean, in the files) - or at least find a way to come back to their original versions once the program is finished. To be clear, I wanna find the most proper way to intercept method calls in PHP. What are your ideas about it ??? Thanks in advance, Rolf

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  • Conversion of pointer-to-pointer between derived and base classes?

    - by Mike Mueller
    Regarding the following C++ program: class Base { }; class Child : public Base { }; int main() { // Normal: using child as base is allowed Child *c = new Child(); Base *b = c; // Double pointers: apparently can't use Child** as Base** Child **cc = &c; Base **bb = cc; return 0; } GCC produces the following error on the last assignment statement: error: invalid conversion from ‘Child**’ to ‘Base**’ My question is in two parts: Why is there no implicit conversion from Child** to Base**? I can make this example work with a C-style cast or a reinterpret_cast. Using these casts means throwing away all type safety. Is there anything I can add to the class definitions to make these pointers cast implicitly, or at least phrase the conversion in a way that allows me to use static_cast instead?

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  • Me As Child Type

    - by Steven
    I have a MustInherit Parent class with two Child classes which Inherit from the Parent. How can I use (or Cast) Me in a Parent function as the the child type of that instance? EDIT: My actual goal is to be able to serialize (BinaryFormatter.Serialize(Stream, Object)) either of my child classes. However, "repeating the code" in each child "seems" wrong.

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  • ruby restrict attr_accessor in subclass

    - by Arivarasan
    I want restrict the access of superclass's method in subclass class Parent attr_accessor :first_name, :last_name def initialize(first_name, last_name) @first_name, @last_name = first_name, last_name end def full_name @first_name + " " + @last_name end end class Son < Parent attr_accessor :first_name def initialize(parent, first_name) @first_name = first_name @last_name = parent.last_name end def full_name @first_name + " " + @last_name end end p = Parent.new("Bharat", "Chipli") puts p.full_name s = Son.new(p, "Harry") s.last_name= "Smith" puts s.full_name here i am getting son's full name as "Harry Smith", but i want "Harry Chipli"

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