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  • Persisting non-entity class that extends an entity (jpa) - example?

    - by Michal Minicki
    The JPA tutorial states that one can have a non-entity that extends entity class: Entities may extend both entity and non-entity classes, and non-entity classes may extend entity classes. - http://java.sun.com/javaee/5/docs/tutorial/doc/bnbqa.html Is it possible to persist such structure? I want to do this: @Entity abstract class Test { ... } class FirstConcreteTest extends Test { ... } // Non-ntity class SecondConcreteTest extends Test { ... } // Non-entity Test test = new FirstConcreteTest(); em.persist(test); What I would like it to do is to persist all fields mapped on abstract Test to a common database table for all concrete classes (first and second), leaving all fields of first and second test class unpersisted (these can contain stuff like EJBs, jdbc pools, etc). And a bonus question. Is it possible to persist abstract property too? @Entity abstract class Test { @Column @Access(AccessType.PROPERTY) abstract public String getName(); } class SecondConcreteTest extends Test { public String getName() { return "Second Concrete Test"; } }

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  • C++ - Where to code a member function for an inherited object.

    - by Francisco P.
    Hello! I have a few classes (heat, gas, contact, pressure) inheriting from a main one (sensor). I have a need to store them in a vector<Sensor *> (part of the specification). At some point in time, I need to call a function that indiscriminately stores those Sensor *. (also part of the specification, not open for discussion) Something like this: for(size_t i = 0; i < Sensors.size(); ++i) Sensors[i]->storeSensor(os) //os is an ofstream kind of object, passed onwards by reference Where and how shall storeSensor be defined? Is there any simple way to do this or will I need to disregard the specification? Mind you, I'm a beginner! Thanks for your time!

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  • How to access the backing field of a base class using fluent nhibernate?

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

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  • Call overidden method in Dojo

    - by nomind
    In dojo, one cannot call a overidden superclass method outside of the same method in the derived class (for which there is this.inherited(), other than that one can call using class_name.function_name.apply). This feature is no longer there because of some refactoring and dojo guys are not going to put it back because they are not convinced about a good enough case for this. Please read this mail thread for details. Isn't there a good enough case for this functionality? Why or why not?

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  • scala: defining a tratit and referencing the corresponding companion object

    - by opensas
    I'm trying to define a trait that uses the corresponding companion object, that is, the componion object of the class using the trait. for example, I have: :paste class Parent { def callMyCompanion = print(Parent.salute) } object Parent { def salute = "Hello from Parent companion object" } class Child extends Parent { } object Child { def salute = "Hello from Child companion object" } And then I create a parent object: scala> val p = new Parent() p: Parent = Parent@1ecf669 scala> p.callMyCompanion Hello from Parent companion object But with a child: scala> val c = new Child() c: Child = Child@4fd986 scala> c.callMyCompanion Hello from Parent companion object I'd like to get: Hello from Child companion object How can I achieve it???

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  • C# private (hidden) base class

    - by Loadmaster
    It is possible to make a C# base class accessible only within the library assembly it's compiled into, while making other subclasses that inherit from it public? For example: using System.IO; class BaseOutput: Stream // Hidden base class { protected BaseOutput(Stream o) { ... } ...lots of common methods... } public class MyOutput: BaseOutput // Public subclass { public BaseOutput(Stream o): base(o) { ... } public override int Write(int b) { ... } } Here I'd like the BaseOutput class to be inaccessible to clients of my library, but allow the subclass MyOutput to be completely public. I know that C# does not allow base classes to have more restrictive access than subclasses, but is there some other legal way of achieving the same effect?

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  • Is it possible to specify a return type of "Derivative(of T)" for a MustOverride sub in VB.NET?

    - by Casey
    VB.NET 2008 .NET 3.5 I have two base classes that are MustInherit (partial). Let's call one class OrderBase and the other OrderItemBase. A specific type of order and order item would inherit from these classes. Let's call these WebOrder (inherits from OrderBase) and WebOrderItem (inherits from OrderItemBase). Now, in the grand scheme of things WebOrder is a composite class containing a WebOrderItem, like so: Public Class WebOrder Inherits OrderBase Public Property OrderItem() as WebOrderItem End Property End Class Public Class WebOrderItem Inherits OrderItemBase End Class In order to make sure any class that derives from OrderBase has the OrderItem property, I would like to do something like this in the OrderBase class: Public MustInherit Class OrderBase Public MustOverride Property OrderItem() as Derivative(Of OrderItemBase) End Class In other words, I want the derived class to be forced to contain a property that returns a derivative of OrderItemBase. Is this possible, or should I be using an entirely different approach?

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  • Calling base class constructor

    - by The Void
    In the program below, is the line Derived(double y): Base(), y_(y) correct/allowed? That is, does it follow ANSI rules? #include <iostream> class Base { public: Base(): x_(0) { std::cout << "Base default constructor called" << std::endl; } Base(int x): x_(x) { std::cout << "Base constructor called with x = " << x << std::endl; } void display() const { std::cout << x_ << std::endl; } protected: int x_; }; class Derived: public Base { public: Derived(): Base(1), y_(1.2) { std::cout << "Derived default constructor called" << std::endl; } Derived(double y): Base(), y_(y) { std::cout << "Derived constructor called with y = " << y << std::endl; } void display() const { std::cout << Base::x_ << ", " << y_ << std::endl; } private: double y_; }; int main() { Base b1; b1.display(); Derived d1; d1.display(); std::cout << std::endl; Base b2(-9); b2.display(); Derived d2(-8.7); d2.display(); return 0; }

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  • Why doesn't C++ allow you to request a pointer to the most derived class?

    - by Matthew Lowe
    (This question should probably be answered with a reference to Stroustrup.) It seems extremely useful to be able to request a pointer to the most derived class, as in the following: class Base { ... }; class DerivedA { ... }; class DerivedB { ... }; class Processor { public: void Do(Base* b) {...} void Do(DerivedA* d) {...} void Do(DerivedB* d) {...} }; list<Base*> things; Processor p; for(list<Base*>::iterator i=things.begin(), e=things.end(); i!=e; ++i) { p.Do(CAST_TO_MOST_DERIVED_CLASS(*i)); } But this mechanism isn't provided in c++. Why?

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  • Having troubles inheriting base class

    - by Nick
    When I inherit the base class, it's telling me there is no such class This is enhanced.h: class enhanced: public changeDispenser // <--------where error is occuring { public: void changeStatus(); // Function: Lets the user know how much of each coin is in the machine enhanced(int); // Constructor // Sets the Dollar amount to what the User wants void changeLoad(int); // Function: Loads what change the user requests into the Coin Machine int dispenseChange(int); // Function: Takes the users amount of cents requests and dispenses it to the user private: int dollar; }; This is enhanced.cpp: #include "enhanced.h" #include <iostream> using namespace std; enhanced::enhanced(int dol) { dollar = dol; } void enhanced::changeStatus() { cout << dollar << " dollars, "; changeDispenser::changeStatus(); } void enhanced::changeLoad(int d) { dollar = dollar + d; //changeDispenser::changeLoad; } This is changeDispenser.h: class changeDispenser { public: void changeStatus(); // Function: Lets the user know how much of each coin is in the machine changeDispenser(int, int, int, int); // Constructor // Sets the Quarters, Dimes, Nickels, and Pennies to what the User wants void changeLoad(int, int, int, int); // Function: Loads what change the user requests into the Coin Machine int dispenseChange(int); // Function: Takes the users amount of cents requests and dispenses it to the user private: int quarter; int dime; int nickel; int penny; }; I didn't include the driver file or the changeDispenser imp file, but in the driver, these are included #include "changeDispenser.h" #include "enhanced.h"

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  • Assigning two strings together getting Access Read Violation

    - by Jay Bell
    I am trying to pass a string to a class mutator and set the private member to that string here is the code that is sending the string void parseTradePairs(Exchange::Currency *curr, std::string *response, int begin, int exit) { int start; int end; string temp; string dataResponse; CURL *tempCurl; initializeCurl(tempCurl); int location = response->find("marketid", begin); if(location <= exit) { start = location + 11; begin = response->find("label", start); end = begin - start - 3; findStrings(start, end, temp, response); getMarketInfo(tempCurl, temp, dataResponse); curr->_coin->setExch(temp); // here is the line of code that is sending the string dataResponse >> *(curr->_coin); curr->_next = new Exchange::Currency(curr, curr->_position + 1); parseTradePairs(curr->_next, response, begin, exit); } } and here is the mutator within the coin class that is receiving the string and assigning it to _exch void Coin::setExch(string exch) { _exch = exch; } I have stepped through it and made sure that exch has the string in it. "105" but soon as it hits _exch = exch; I get the reading violation. I tried passing as pointer as well. I do not believe it should go out of scope. and the string variable in the class is initialized to zero in the default constructor but again that should matter unless I am trying to read from it instead of writing to it. /* defualt constructor */ Coin::Coin() { _id = ""; _label = ""; _code= ""; _name = ""; _marketCoin = ""; _volume = 0; _last = 0; _exch = ""; } Exchange::Exchange(std::string str) { _exch = str; _currencies = new Currency; std::string pair; std::string response; CURL *curl; initializeCurl(curl); getTradePairs(curl, response); int exit = response.find_last_of("marketid"); parseTradePairs(_currencies, &response, 0, exit); } int main(void) { CURL *curl; string str; string id; Coin coin1; initializeCurl(curl); Exchange ex("cryptsy"); curl_easy_cleanup(curl); system("pause"); return 0; } class Exchange { public: typedef struct Currency { Currency(Coin *coin, Currency *next, Currency *prev, int position) : _coin(coin), _next(next), _prev(prev), _position(position) {} Currency(Currency *prev, int position) : _prev(prev), _position(position), _next(NULL), _coin(&Coin()){} Currency() : _next(NULL), _prev(NULL), _position(0) {} Coin *_coin; Currency *_next; Currency *_prev; int _position; }; /* constructor and destructor */ Exchange(); Exchange(std::string str); ~Exchange(); /* Assignment operator */ Exchange& operator =(const Exchange& copyExchange); /* Parse Cryptsy Pairs */ friend void parseTradePairs(Currency *curr, std::string *response, int begin, int exit); private: std::string _exch; Currency *_currencies; }; here is what i changed it to to fix it. typedef struct Currency { Currency(Coin *coin, Currency *next, Currency *prev, int position) : _coin(coin), _next(next), _prev(prev), _position(position) {} Currency(Currency *prev, int position) : _prev(prev), _position(position), _next(NULL), _coin(&Coin()){} Currency() { _next = NULL; _prev = NULL; _position = 0; _coin = new Coin(); } Coin *_coin; Currency *_next; Currency *_prev; int _position; };

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  • What's an elegant solution to get the property values from two classes (that have the same property

    - by SlipToFall
    Essentially I have to deal with a poorly implemented web service. They have two classes that don't derive from a parent class, but have the same properties (Ughh...). So it looks like this in my web service proxy class file: public partial class Product1 { public int Quantity; public int Price; } public partial class Product2 { public int Quantity; public int Price; } So what's the best way to grab the values from known properties without duplicating the code and casting to their respective classes? I know I probably could use reflection, but that can get ugly. If there is an easier less crazier way to do it (maybe in the new c# features?) please let me know.

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  • How can one enforce calling a base class function after derived class constructor?

    - by Mike Elkins
    I'm looking for a clean C++ idiom for the following situation: class SomeLibraryClass { public: SomeLibraryClass() { /* start initialization */ } void addFoo() { /* we are a collection of foos */ } void funcToCallAfterAllAddFoos() { /* Making sure this is called is the issue */ } }; class SomeUserClass : public SomeLibraryClass { public: SomeUserClass() { addFoo(); addFoo(); addFoo(); // SomeUserClass has three foos. } }; class SomeUserDerrivedClass : public SomeUserClass { public: SomeUserDerrivedClass() { addFoo(); // This one has four foos. } }; So, what I really want is for SomeLibraryClass to enforce the calling of funcToCallAfterAllAddFoos at the end of the construction process. The user can't put it at the end of SomeUserClass::SomeUserClass(), that would mess up SomeUserDerrivedClass. If he puts it at the end of SomeUserDerrivedClass, then it never gets called for SomeUserClass. To further clarify what I need, imagine that /* start initialization */ acquires a lock, and funcToCallAfterAllAddFoos() releases a lock. The compiler knows when all the initializations for an object are done, but can I get at that information by some nice trick?

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  • Reading a Text file in xcode

    - by Nicolaj Zefting
    First off, I'm a complete beginner. This might be a stupid question, but here it goes: I'm currently working on an App than contains Latin texts that the users can view and read. I'm using Xcode 4 with the storybord function. Theway the app is built: user selects author - then the book - then app shows the text. I am kind of confused because i need to have various text files, depending on the users choice.

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  • C++ Problem: Class Promotion using derived class

    - by Michael Fitzpatrick
    I have a class for Float32 that is derived from Float32_base class Float32_base { public: // Constructors Float32_base(float x) : value(x) {}; Float32_base(void) : value(0) {}; operator float32(void) {return value;}; Float32_base operator =(float x) {value = x; return *this;}; Float32_base operator +(float x) const { return value + x;}; protected: float value; } class Float32 : public Float32_base { public: float Tad() { return value + .01; } } int main() { Float32 x, y, z; x = 1; y = 2; // WILL NOT COMPILE! z = (x + y).Tad(); // COMPILES OK z = ((Float32)(x + y)).Tad(); } The issue is that the + operator returns a Float32_base and Tad() is not in that class. But 'x' and 'y' are Float32's. Is there a way that I can get the code in the first line to compile without having to resort to a typecast like I did on the next line?

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  • Make sure base method gets called in C#

    - by Fnatte
    Can I somehow force a derived class to always call the overridden methods base? public class BaseClass { public virtual void Update() { if(condition) { throw new Exception("..."); // Prevent derived method to be called } } } And then in a derived class : public override void Update() { base.Update(); // Forced call // Do any work } I've searched and found a suggestion to use a non-virtual Update() but also a protected virtual UpdateEx(). It just doesn't feel very neat, isn't there any better way? I hope you get the question and I am sorry for any bad English.

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  • calling a function from a set of overloads depending on the dynamic type of an object

    - by Jasper
    I feel like the answer to this question is really simple, but I really am having trouble finding it. So here goes: Suppose you have the following classes: class Base; class Child : public Base; class Displayer { public: Displayer(Base* element); Displayer(Child* element); } Additionally, I have a Base* object which might point to either an instance of the class Base or an instance of the class Child. Now I want to create a Displayer based on the element pointed to by object, however, I want to pick the right version of the constructor. As I currently have it, this would accomplish just that (I am being a bit fuzzy with my C++ here, but I think this the clearest way) object->createDisplayer(); virtual void Base::createDisplayer() { new Displayer(this); } virtual void Child::createDisplayer() { new Displayer(this); } This works, however, there is a problem with this: Base and Child are part of the application system, while Displayer is part of the GUI system. I want to build the GUI system independently of the Application system, so that it is easy to replace the GUI. This means that Base and Child should not know about Displayer. However, I do not know how I can achieve this without letting the Application classes know about the GUI. Am I missing something very obvious or am I trying something that is not possible?

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  • Dynamic Object Not Creating for Privately Inherited Class.

    - by mahesh
    Hi, What is the reason for the following code that does not let me to create object. class base { public: void foo() { cout << "base::foo()"; } }; class derived : private base { public: void foo() { cout << "deived::foo()"; } }; void main() { base *d = new derived(); d->foo(); } It Gives me error : " 'type cast' : conversion from 'derived *' to 'base *' exists, but is inaccessible" Thanks in advance :)

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  • Generics in a bidirectional association

    - by Verhoevenv
    Let's say I have two classes A and B, with B a subtype of A. This is only part of a richer type hierarchy, obviously, but I don't think that's relevant. Assume A is the root of the hierarchy. There is a collection class C that keeps track of a list of A's. However, I want to make C generic, so that it is possible to make an instance that only keeps B's and won't accept A's. class A(val c: C[A]) { c.addEntry(this) } class B(c: C[A]) extends A(c) class C[T <: A]{ val entries = new ArrayBuffer[T]() def addEntry(e: T) { entries += e } } object Generic { def main(args : Array[String]) { val c = new C[B]() new B(c) } } The code above obviously give the error 'type mismatch: found C[B], required C[A]' on the new B(c) line. I'm not sure how this can be fixed. It's not possible to make C covariant in T (like C[+T <: A]) because the ArrayBuffer is non-variantly typed in T. It's not possible to make the constructor of B require a C[B] because C can't be covariant. Am I barking up the wrong tree here? I'm a complete Scala newbie, so any ideas and tips might be helpful. Thank you! EDIT: Basically, what I'd like to have is that the compiler accepts both val c = new C[B]() new B(c) and val c = new C[A]() new B(c) but would reject val c = new C[B]() new A(c) It's probably possible to relax the typing of the ArrayBuffer in C to be A instead of T, and thus in the addEntry method as well, if that helps.

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  • About calling an subclass' overriding method when casted to its superclass

    - by Omega
    #include <iostream> class Vehicle { public: void greet() { std::cout << "Hello, I'm a vehicle"; } }; class Car : public Vehicle { public: void greet() { std::cout << "Hello, I'm a car"; } }; class Bike : public Vehicle { public: void greet() { std::cout << "Hello, I'm a bike"; } }; void receiveVehicle(Vehicle vehicle) { vehicle.greet(); } int main() { receiveVehicle(Car()); return 0; } As you can see, I'm trying to send a parameter of type Vehicle to a function, which calls greet(). Car and Bike are subclasses of Vehicle. They overwrite greet(). However, I'm getting "Hello, I'm a vehicle". I suppose that this is because receiveVehicle receives a parameter of type Vehicle instead of a specific subclass like Car or Bike. But that's what I want: I want this function to work with any subclass of Vehicle. Why am I not getting the expected output?

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  • Base form controls not visible in child form

    - by Kildareflare
    Hello I'm using C#.Net and have a base form that is inherited by several forms. Until yesterday, when the child (derived) form was opened in the designer the base forms controls would be displayed and shown as locked. Now, however the form is simply blank. None of the base forms controls are visible in the designer. Everything compiles, builds and runs OK. Has anyone else seen this? I've tried placing a call to the base forms InitializeComponent method in the derived forms OnLoad method but to no avail.

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  • Calling base Text method on custom TextBox

    - by The Demigeek
    I'm trying to create a CurrencyTextBox that inherits from TextBox. I'm seeing some really weird behavior that I just don't understand. After lots of testing, I think I can summarize as follows: In the class code, when I access base.Text (to get the textbox's text), I'm actually getting the return value of my overridden Text property. I thought the base keyword would ensure that the underlying object's methods get called. To demonstrate: public class cTestTextBox : System.Windows.Forms.TextBox { string strText = ""; public cTestTextBox() { SetVal("AAA"); base.Text = "TEST"; } public override string Text { get { string s = strText; s = "++" + s + "++"; return s; } } public void SetVal(string val) { strText = val; } } Place this control on a form and set a breakpoint on the constructor. Run the app. Hover your mouse over the base.Text expression. Note that the tooltip shows you the value of the overridden property, not the base property. Execute the SetVal() statement and again hover your mouse over the base.Text expression. Note that the tooltop shows you the value of the overridden property, not the base property. How do I reliably access the Text property of the textbox from which I'm inheriting?

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