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• XSD: xs:sequence & xs:choice combination for xs:extension elements of a common base type?

  - by bguiz

  Hi, My question is about defining an XML schema that will validate the following 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 (feeble) 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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• Me As Child Type In General Function

  - 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. EDIT2: This is my Serialize function. Where should I implement this function? Copying and pasting to each child doesn't seem right, but casting the parent to a child doesn't seem right either. Public Function Serialize() As Byte() Dim bFmt As New BinaryFormatter() Dim mStr As New MemoryStream() bFmt.Serialize(mStr, Me) Return mStr.ToArray() End Function

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• C++ superclass constructor calling rules

  - by levik

  What are the C++ rules for calling the superclass constructor from a subclass one?? For example I know in Java, you must do it as the first line of the subclass constructor (and if you don't an implicit call to a no-arg super constructor is assumed - giving you a compile error if that's missing).

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• Scala: Mixing traits with private fields

  - by Vilius Normantas

  It's not much of a question, it's rather my excitement that it's possible at all! I wrote this little example just to prove the opposite - I expected either a compiler error or one of the values (111 or 222, I wasn't sure). scala> trait T1 { private val v = 111; def getValueT1 = v } scala> trait T2 { private val v = 222; def getValueT2 = v } scala> class T12 extends T1 with T2 scala> val t = new T12 scala> t.getValueT1 res9: Int = 111 scala> t.getValueT2 res10: Int = 222 Why doesn't the v get overridden? Off course this works only as long as vs are private, but still.

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• C#: is there way for a class to 'remove' methods that it has inherited

  - by Craig Johnston

  Is there way for a class to 'remove' methods that it has inherited? eg. If I don't want my class to have a ToString() method can I do something so that it is no longer available?

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• ActiveRecord Validations for Models with has_many, belongs_to associations and STI

  - by keruilin

  I have four models: User Award Badge GameWeek The associations are as follows: User has many awards. Award belongs to user. Badge has many awards. Award belongs to badge. User has many game_weeks. GameWeek belongs to user. GameWeek has many awards. Award belongs to game_week. Thus, user_id, badge_id and game_week_id are foreign keys in awards table. Badge implements an STI model. Let's just say it has the following subclasses: BadgeA and BadgeB. Some rules to note: The game_week_id fk can be nil for BadgeA, but can't be nil for BadgeB. Here are my questions: For BadgeA, how do I write a validation that it can only be awarded one time? That is, the user can't have more than one -- ever. For BadgeB, how do I write a validation that it can only be awarded one time per game week?

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• How can I create activerecord models that are subsets of a certain model?

  - by gsiener

  I've seen this before but can't figure out what the correct term is. Basically, I'd like to create models for a specific subset of table data. E.g. (these are not the real classes) class Person < ActiveRecord::Base class Man < Person <something here> :gender => 'male'

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• Generics and Derived Classes .NET 3.5

  - by Achilles

  Consider the following where class "Circle" inherits from "Shape": dim objListOfCircles as new List(of Circle) DrawShapes(objListOfCirlces) Private sub DrawShapes(byref objListOfShapes as List(of Shape)) for each objShape as Shape in objListOfShapes objShape.Draw() next end sub I can't get this to work. What is the explaination as to why this doesn't work?

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• django access to parent

  - by SledgehammerPL

  model: class Product(models.Model): name = models.CharField(max_length = 128) (...) def __unicode__(self): return self.name class Receipt(models.Model): name = models.CharField(max_length=128) (...) components = models.ManyToManyField(Product, through='ReceiptComponent') def __unicode__(self): return self.name class ReceiptComponent(models.Model): product = models.ForeignKey(Product) receipt = models.ForeignKey(Receipt) quantity = models.FloatField(max_length=9) unit = models.ForeignKey(Unit) def __unicode__(self): return unicode(self.quantity!=0 and self.quantity or '') + ' ' + unicode(self.unit) + ' ' + self.product.genitive And now I'd like to get list of the most often useable products: ReceiptComponent.objects.values('product').annotate(Count('product')).order_by('-product__count' the example result: [{'product': 3, 'product__count': 5}, {'product': 6, 'product__count': 4}, {'product': 5, 'product__count': 3}, {'product': 7, 'product__count': 2}, {'product': 1, 'product__count': 2}, {'product': 11, 'product__count': 1}, {'product': 8, 'product__count': 1}, {'product': 4, 'product__count': 1}, {'product': 9, 'product__count': 1}] It's almost what I need. But I'd prefer having Product object not product value, because I'd like to use this in views.py for generating list.

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• How do you make a private member in the base class become a public member in the base class?

  - by jasonline

  Consider the following code: class Base { void f() { } }; class Derived: public Base { public: }; What can you change in the derived class, such that you can perform the following: Derived d; d.f(); If the member is declared as public in the base class, adding a using declaration for Base::f in the derived class public section would've fix the problem. But if it is declared as private in the base class, this doesn't seem to work.

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• Is it possible to override a property and return a derived type in VB.NET?

  - by Casey

  Consider the following classes representing an Ordering system: Public Class OrderBase Public MustOverride Property OrderItem() as OrderItemBase End Class Public Class OrderItemBase End Class Now, suppose we want to extend these classes to a more specific set of order classes, keeping the aggregate nature of OrderBase: Public Class WebOrder Inherits OrderBase Public Overrides Property OrderItem() as WebOrderItem End Property End Class Public Class WebOrderItem Inherits OrderItemBase End Class The Overriden property in the WebOrder class will cause an error stating that the return type is different from that defined in OrderBase... however, the return type is a subclass of the type defined in OrderBase. Why won't VB allow this?

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• A general declaration for all inherited classes

  - by Soham

  Consider, there is a class called SuperClass from which, ClassA, ClassB, ClassC is derived. From each one of those derived Classes, there are further more two classes are derived each called ChildClassAA and ChildClassAB[AB stands for Bth Child class from the Ath Class.Lets not really pull our hair on this nomenclature]. Now, ideally, I want to declare a general type as a private member of another Class say IndependentClass which can be initialized during run time as either of the objects of type ClassAor ClassB or ClassC and even the derived classes like ClassAA or ClassAB. Is there a possible way to do it?

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• In Java, is it possible for a super constructor invocation actually invoke a constructor in the calling class?

  - by John Assymptoth

  Super constructor invocation definition: [Primary.] [NonWildTypeArguments] super ( ArgumentListopt ) ; A super constructor call can be prefixed by an Primary expression. Example (taken from JLS): class Outer { class Inner{ } } class ChildOfInner extends Outer.Inner { ChildOfInner() { (new Outer()).super(); // (new Outer()) is the Primary } } Does a Primary expression exist that makes the call to super() the invocation of a constructor of the calling class? Or Java prevents that?

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• How to change position of inherited items in an Inherited user control

  - by Yalda

  I have used a user control as a base class (let's call it BaseUC) with 3 labels (in 3 lines) on it (they are set as protected). And there is another user control that inherits from it (InheritedUC). I have added two more labels in InheritedUC, which are positioned between the base's labels (so there are 5 lines). Everything is fine is Visiual Studio's design UI view. But when I run the application, labels on BaseUC overlap with the ones in InheritedUC and I can't see the ones on the inherited control. Any ideas to fix this? Thank you very much

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• Doing things with objects as if they were parents

  - by General Ackbar

  Sorry that this is probably a super noob question. But the following code give me an error saying that there are invalid arguments in my call of doStuffToLines(segments) shouldnt I be able to do this since I have my DimensionLineSegment inherits from Lines? private void doStuff() { List<DimensionLineSegment> segments = new List<DimensionLineSegment>(); doStuffToLines(segments); } private void doStuffToLines(List<Line> lines) { }

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• Javascript inherance and use of super: is this possible?

  - by Totty

  var Parent = function(value){ this.value = value; this.value1 = 3; this.hello = function(text){ alert(this.value1 + text); } } var Child = extends(Parent, function(value){ this.value1 = 1; this.hello = function(text){ this.super.hello(text); alert('Child' + this.value1 + this.value); } }) var child = new Child(2); child.hello('ola'); // this must output 2 alerts: // 1: "1ola" // 2: "Child1ola"

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• Java: using generic wildcards with subclassing

  - by gibberish

  Say I have a class Foo, a class A and some subclass B of A. Foo accepts A and its sublclasses as the generic type. A and B both require a Foo instance in their constructor. I want A's Foo to be of type A , and B's Foo to be of type B or a superclass of B. So in effect, So I only want this: Foo<X> bar = new Foo<X>; new B(bar); to be possible if X is either A, B, or a both subclass of A and superclass of B. So far this is what I have: class Foo<? extends A>{ //construct } class A(Foo<A> bar){ //construct } class B(Foo<? super B> bar){ super(bar); //construct } The call to super(...) doesn't work, because <A> is stricter than <? super B>. Is it somehow possible to use the constructor (or avoid code duplication by another means) while enforcing these types? Edit: Foo keeps a collection of elements of the generic parameter type, and these elements and Foo have a bidirectional link. It should therefore not be possible to link an A to a Foo.

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• (Cocoa) Can I Subclass and Delegate at the same time?

  - by Alvin

  @interface ClassB <ClassADelegate> : ClassA id <ClassBDelegate> delegate; @end As the code says, ClassB subclasses from ClassA and handles the formation protocol of Class A. However, the variable "delegate" will be duplicated. (ClassA also has "delegate") In fact, it can be done without subclassing, but it seems the code is cumbersome, i.e., to use a variable/function of ClassA, I need to write [[ClassB classA] doSomething] instead of [classB doSomething], where doSomething: is a function of ClassA. Are there any tidy way for me to do that?

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• How to override the attr_protected?

  - by KandadaBoggu

  I have STI implementation as follows: class Automobile < ActiveRecord::Base end class Car < Automobile end class Truck < Automobile end class User < ActiveRecord::Base has_many :automobiles accepts_nested_attributes_for :automobiles end I am creating a list of automobiles for a user. For each automobile, the UI sets the type field and the properties associated with the automobile.While form submission, the type field is ignored as it is a protected attribute. How do I work around this issue? Is there a declarative way to unprotect a protected attribute?

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• Confused about "override" vs. "new" in C#

  - by iTayb

  I'm having the following classes: class Base { public virtual void Print() { Console.WriteLine("Base"); } } class Der1 : Base { public new virtual void Print() { Console.WriteLine("Der1"); } } class Der2 : Der1 { public override void Print() { Console.WriteLine("Der2"); } } This is my main method: Base b = new Der2(); Der1 d1 = new Der2(); Der2 d2 = new Der2(); b.Print(); d1.Print(); d2.Print(); The output is Base, Der2, Der2. As far as I know, Override won't let previous method to run, even if the pointer is pointing to them. So the first line should output Der2 as well. However Base came out. How is it possible? How the override didn't work there?

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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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• When should you not use virtual destructors?

  - by Mag Roader

  Is there ever a good reason to not declare a virtual destructor for a class? When should you specifically avoid writing one?

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• question about class derivation in c++?

  - by jack22

  hi, i want to know some things about class derivation in c++ so i have super class x and an inherited class y and i did this class x{ public:a; private:b; protected:c; } class y:public x{ public:d; } in this case how y can access a,b,and c and by how i mean(public,protected,private) the second case: class x{ public:a; private:b; protected:c; } class y:private x{ public:d; } the same question? the third case: class x{ public:a; private:b; protected:c; } class y:private x{ public:d; } again the same question? sorry i think i wrote too much bye

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• How to save derived type (TPT) in Entity Framework?

  - by Peter Stegnar

  I have problems with saving derived type (TPT) with Entity Framework to database. Let's say I have base entity Animal and derived type Dog. I want to save Dog entity. I thought that I could do it like contex.AddToDogs(), but contex contain only base entity - Animal. So I can only save Animal object - contex.AddToAnimals(). I have also tried with contex.AddObject("Animals", dogInstance), but I get the following error: The member with identity 'NavigationProperty' does not exist in the metadata collection. But I have add EntityReference to the "NavigationProperty". So how to save derived type in EF?

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• Consequences in PHP of implementing an interface through two different routes?

  - by Daniel Bingham

  What are the consequences of implementing the same interface through two different routes in PHP, are there any? What I mean, is something like this: interface baseInterface {} abstract class baseClass implements baseInterface { } interface myInterface extends baseInterface {} class myClass extends baseClass implements myInterface {} In this case myClass implements baseInterface from two different parents - myInterface and baseClass. Are there any consequences to this? My instinct is that PHP should handle this fine, but I just want to make sure. What exactly does PHP do in this case? Does it just check to see that the necessary functions are implemented for the interface each time it discovers it and call it a day or does it do something more?

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