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OOP abstract classes when to implement abstract methods
Generally, you should implement all methods in the last common ancestor. So if you want your children classes will behave the same way, implement them now. If they are to be implemented, but in many ways by different classes, leave them abstract. Actually, an abstract class is done only for requiring that if somebody will inherit something from this common class, he will provide these methods (abstract class is something similar to interface). If you implement all of them, there is no need to use an abstract class.

Categories : PHP

PHP design- abstract classes and factory methods
That sound correct to use abstract base class, as long as you are sure to never need to instantiate Order_Export : abstract class Order_Export { abstract protected function someMeth1(); abstract protected function someMeth2(); public function someMeth3() { // Do common thing to both Order_WooExport and Order_WPExport // using someMeth1(), someMeth2()... } } Then : class Order_WooExport extends Order_Export { protected function someMeth1() { // Do something specific } protected function someMeth2() { // Do something specific } } Finally, the factory seems to be the right way to go too.

Categories : PHP

What is the best practice for abstract classes with overridable methods which return nothing
It is really up to you to decide how you indicate "I don't know". But returning Nothing from an abstract base class is a pretty lousy habit. It is liable to generate NullReferenceException in the client code when either the programmer that derives from your class or the programmer that writes the client code doesn't realize that Nothing is a possible value. NRE is a lousy exception to diagnose, the CLR is not capable of giving any meaningful hint about it. It cannot possibly name a variable that stores the null for example, it knows Nothing. This gets especially difficult to diagnose because the null got generated at least two levels away from where this goes wrong. The user that is saddled with the crash might have to talk to three programmers to get to the bottom of the problem. A

Categories : Dotnet

Why do abstract class methods in PHP require same signatures as child classes?
This is a good and interesting question. In a case like GeometricShape(), GetArea would be without arguments. A better example would be an abstract method called FillColor that takes the color as an argument like so: abstract class GeometricShape { abstract function GetArea(); abstract function FillColor($color); } class Square extends GeometricShape { function GetArea() { echo "Square - get area "; } function FillColor($color) { echo "Square - Filling color $color "; } } class Circle extends GeometricShape { function GetArea() { echo "Circle - get area "; } function FillColor($color) { echo "Circle - Filling color $color "; } } $square = new Square(); $square->FillColor('green'); $cir

Categories : PHP

Access to inherited children's variables of abstract class from another children of same abstract class
Your code works for me! I do not get a fatal error. The only thing I get is a notice because of the typo inside $this->variable in the child2 class. The original variable is incorrectly spelled "varialbe", but used consistently. Fixing the typo lets the code run completely error-free. So you fail to demonstrate the problem. Update your question if you find why the issue isn't included in your code. It must be somewhere else. And make sure you actually run your code before using it as an example, and that it has the problem you describe.

Categories : PHP

Abstract domain classes in GORM: how to deal with static GORM methods
As in Java, the answer is likely to involve passing a Class object to the AbstractParser constructor. public abstract class AbstractParser<T extends Entity> { protected Class<T> entityClass protected AbstractParser(Class<T> entityClass) { this.entityClass = entityClass } protected void parseAndSavePages(){ //Do some parsing ... // Groovy treats instance method calls on a Class object as calls // to static methods of the corresponding class entityClass.withTransaction { if(entityClass.findEntityById(entity.id)){ println "Already exists!"; } else { entity.save(failOnError: true); } } } } class PersonParser extends AbstractPar

Categories : Grails

Extending an abstract class - implementing abstract methods
You have to provide an implementation to all abstract methods. Even if no part of the program calls them now a class can be created in the future that does call them, or the super class implementation may be changed. A stub is needed even if it's just for binary compatibility.

Categories : Java

Abstract class with all methods abstract - Practical Example
The only practical approach i think is that Abstract class can hold state. So you can have inside properties with access level protected, and you can make protected abstract methods that in interface you can't cause all are public. A practical example could be for example this, the protected method in java has 'inheritance access' and 'package access'. public interface Operation{ void operate(); } public abstract class AbstractClase implements Operation{ protected Operation delegate; public AbstractClase(Operation delegate){ this.delegate=delegate; } //delegate implementation responsability to children protected abstract doSomething(); } The downside of using abstract class is that you loss the possibility to extends of something else too.

Categories : Java

Java Abstract Classes: Returning "this" pointer for derived classes
unfortunately not. It would be good if you could do this public this withId(final String Id) { // doesn't work this.Id = Id; return this; } or just public this withId(final String Id) { // doesn't work either this.Id = Id; } or it would know that "void" methods are implicitly chained (as I believe one formal proposal suggested)

Categories : Java

Use of an abstract class without any abstract methods
You can make a class as abstract ,even if you don't want to implement all of the interface methods that the class implements. According to java docs. It was noted that a class that implements an interface must implement all of the interface's methods. It is possible, however, to define a class that does not implement all of the interface methods, provided that the class is declared to be abstract. Any way you can't instantiate a class that declared with abstract.

Categories : Java

How to apply rule to classes when they are children of either of two parent classes?
Try the :not css selector: .special-price:not(.product-view) { } More information: https://developer.mozilla.org/en-US/docs/Web/CSS/:not JSFiddle: http://jsfiddle.net/b2bjJ/

Categories : CSS

Abstract methods and hiding methods
No, you can't. They must have virtual keyword. Good example here,similarThis one as well

Categories : C#

Alternative to static nested classes in C# for grouping a classes public methods?
Employee theEmployee = new Employee(); Would give you an Employee object to work with. With this you could change the values of the Employee class from DataBaseHandler

Categories : C#

When do I really need to use Abstract Methods?
Unless you have things that must be done for all shapes at the beginning or ending of the draw call, then you wouldn't put code in the abstract class to do it. If there are common things to be done that are done at different points during draw, then you can put them in the abstract class in, say, protected methods; only classes that inherit will be able to call them, and that will put that common code into one place. The use of abstract methods is to ensure that (1) a class using a shape has access to those methods without knowing what subclass it holds a reference to. So, for instance, a page could have a list of shapes, and call draw on each one (because it is defined in the superclass) even though each one is a specific subclass shape. If draw() is not defined in shape, then you can

Categories : C#

Send Abstract Classes via the API
I don't think so. The general problem you are trying to solve doesn't always have a viable solution, as you'd need to combine all the properties of Transaction and any extending classes. Consider these classes: public abstract class Foo { //... } public class Bar extends Foo { public String prop; // getters and setters } public class Baz extends Foo { public Integer prop; // getters and setters } Should the conglomeration of classes represented on the client side by Foo contain a prop field that is a String or an Integer? If you want to allow anything extending Foo be sent over the wire, you must provide all the properties you want sent as part of Foo.

Categories : Java

Abstract Methods don't have body?
Also read docs When an abstract class is subclassed, the subclass usually provides implementations for all of the abstract methods in its parent class. However, if it does not, the subclass must also be declared abstract.

Categories : Java

Testing abstract classes in Python
Make a subclass of the abstract class, then test the subclass. from abc import ABCMeta, abstractmethod class ThisIsAnAbstractClass(object): __metaclass__ = ABCMeta # <-- @abstractmethod def __init__(self, parameter): self.parameter = parameter def do_something(): """do something""" class ConcreteClass(ThisIsAnAbstractClass): def __init__(self, parameter): super(ConcreteClass, self).__init__(parameter) try: ThisIsAnAbstractClass('test') assert False, 'Abstract class instance created!' except TypeError: pass assert ConcreteClass('test').parameter == 'test' NOTE: You should use abc.ABCMeta as a metaclass.

Categories : Python

Java abstract classes which throw
Because of Polymorphism. Since, at runtime the actual object's type in the Collection is B so, B.foo() was called. Basically, if you have a sub-type object assigned to a super-class reference the runtime polymorphism makes sure that the sub-type's version of an instance method gets called i.e. if it has been overridden of course. If not, the call falls back upon the super-class version. What qualifies as a valid method override? An overridden method must have the same method signature a covariant return type (a sub-type can be returned) must not throw broader checked exceptions (applies to your question and @Dgrin91's comment i.e. just because the overridden method took some risks (threw exceptions) doesn't mean that the overriding method should do the same; so, it may not throw any

Categories : Java

Abstract classes and Fluent Nhibernate
If you want all your cars to be persisted in the same table, you need to implement a mapping strategy called table per class hierarchy. First, map your abstract class as below: public class CarMap : ClassMap<Car> { public CarMap() { Id(x => x.Id); Map(x => x.Color); Map(x => x.Model); Map(x => x.Name); DiscriminateSubClassesOnColumn("Type"); } } The table will have a "Type" column. This is called the discriminator column. Then map all your concrete classes. Each concrete class will have a "discriminator value": public class SportCarMap : SubclassMap<Car> { public SportCarMap() { DiscriminatorValue("SportCar"); //If your Sport Car has specific properties: //Map(x => x.BrakeH

Categories : C#

Java Referencing Abstract Classes
just replace public class MyFirstQuest { name = "A quest"; id = 0; } by public class MyFirstQuest extends Quest{ public MyFirstQuest(){ name = "A quest"; id = 0; } } and there are some tips : use private variables and use getters like this public String getName(){return name;} remove the abstract of the method getPrerequisite

Categories : Java

Java abstract classes and inheritance
Uncompilable source code - CarLoan is not abstract and does not override abstract method setPrice5() in PersonalLoan Compiler error message is clear. You haven't provided implementation for setPrice5() in PersonalLoan class. Like setPrice5() method in HomeLoan class, you need to add setPrice5() method to PersonalLoan class also.

Categories : Java

Assigning abstract base classes
When your Button class has a property called i.e. ButtonImage, but your Control class doesn't have, you wont be able to access it when numerate through a control List. Though, your object will be kind of "downgraded" (not practically) when saving it as a Control.

Categories : C#

Symfony2 Payum Abstract Methods
Actually i commented PayumRequestStatusRequestInterface::getModel() function, but i'm pretty sure that this isn't the right way to fix it Nice catch! I will remove these methods (getModel and setModel) on StatusRequestInterface interface. They come from previous version and should not be there any longer. The bad thing is I can remove them only since version 0.6 as it introduce BC break.

Categories : PHP

Implement abstract methods with a def macro
Are you sure you did test with the macro compiled first and AImpl later? Using a forwarder method like your second try seems to work (with 2.10.2): // first compilation run import scala.reflect.macros.Context import language.experimental.macros trait A { def foo(): Unit } object AImplMacros { def fooImpl(c: Context)(): c.Expr[Unit] = { import c.universe._ c.Expr[Unit](reify().tree) } } // second compilation run trait AImpl extends A { def foo(): Unit = bar() def bar(): Unit = macro AImplMacros.fooImpl } // compiles and runs: scala> val a = new AnyRef with AImpl a: AImpl = $anon$1@59225446 scala> a.foo scala> a.bar

Categories : Scala

Accessing Abstract Class Methods C#,ASP.net
You would need to create an instance of Y. Since it's abstract, you would have to create some subclass of it. public class SubY : Y { } Then in your code write something like: var suby = new SubY(); int r2 = suby.M2(10, 5); //15

Categories : C#

How To Make Abstract Class And Inherit In Other Classes
Looks like you should be able to combine them this way: public interface ITarget { string LocalConfigPath { get; } string LocalVersion { get; } IDictionary<string, string> LocalFiles { get; } } public interface ISource { string AvailConfigPath { get; } string AvailVersion { get; } IDictionary<string, string> AvailFiles { get; } } internal abstract class BaseClass { public virtual string ConfigPath { get; } private XDocument document = XDocument.Load(ConfigPath); public string Version { get { return document.Root .Element("InfoConfigFile") .Attribute("version").Value; } } public IDictionary<string, string> Files { get {

Categories : C#

Abstract base classes that implement an interface
Since Item inherits from IDisplayable, anything that derives from Item must also implement IDisplayable. So explicitly adding IDisplayable to those classes is redundant. EDIT: @EricLippert makes an excellent point below about the effect of re-implementing interfaces. I'm leaving this answer to preserve the discussion in the comments.

Categories : C#

abstract classes which implements an interface uncomplete
Keep in mind that when you instantiate a subclass and refer it as super/abstract class or interface, it's still the instance of the subclass. Any method called on the object bubbles up from subclass to super class if its not available in the sub class. Thus if you have: interface GemeInterface getStartScreen() getCloseScreen() abstract class AndroidGame implement GemeInterface getCloseScreen() class MrNomGame extends AndroidGame getStartScreen() class MrPetNomGame extends AndroidGame getStartScreen() and using as //You can't instantiate AndroidGame hence the it has to be instance of a subclass AndroidGame androidGame1 = new MrNomGame (); androidGame1.getStartScreen(); //You can't instantiate AndroidGame hence the it has to be insta

Categories : Java

Do traits make abstract classes useless?
Generally traits are used for abstract functionality that might be needed by many classes that are not part of the same class hierarchy. You could use a trait to keep this functionality in a single location and apply it across a number of classes. This doesn't remove the usefulness of abstract classes, but it does potentially remove the need for static utility classes one might typically put these type of functions in.

Categories : PHP

What is the best way to call methods from all the subclasses of an abstract class?
You want to call a method on each instances of subclasses of an abstract class. There is no automatic way to find all the instances of a class anyway, so you need to manage the list of all instances yourself. You have to do one of the following: manage the list manually, that is add instances to the list when you create them make that more automated, by adding the instance to a static list in the constructor of your base class ApiService. But it makes the base class aware of the list of its instances, and it seems to me a bit of a code smell. There is another alternative, when you know the number of instances in your application in advance: use an Enum instead of an abstract class. Each Enum value is an instance of the class, and it can implement interfaces and methods, and each inst

Categories : Java

Non-virtual methods in abstract base class
Welcome to C++: referencing uninitialized values causes undefined behavior. biT is not initialized before being referenced. One possible way to do so would be to tell the object what color you want it to be at creation. Also, you're eventually going to want to delete that object you created with new, but doing so will also invoke undefined behavior since you haven't defined a virtual destructor in the base class. class Dad { public: Dad(bool b) : biT(b) {} virtual ~Dad() {} virtual void Void() =0; bool biT; bool getBit(){return biT;} }; class Kid: public Dad { public: Kid(bool b) : Dad(b) {} void Void(){} }; int main() { Dad* dP = new Kid(false); cout<<dP->getBit(); delete dP; }

Categories : Misc

Implement abstract methods from inherited class
You can do it with some method-by-method boilerplate. class A { public: virtual int methodA() = 0; virtual int methodB() = 0; virtual int methodC() = 0; }; class B { //B implements A.A() and A.B() public: int methodA() { return 0; }; int methodB() { return 0; }; }; class C : public A, public B { public: int methodA() { return B::methodA(); } int methodB() { return B::methodB(); } int methodC() { return 0; }; //C implements A.C() }; Demo: http://ideone.com/XDKDW9

Categories : C++

How to abstract parts of a method into "sub-methods" (Python)
My opinion is that you don't need to repeat (parts of) the class name in its methods, because when possible you will no be able to employ duck typing. So you will want to create methods of EmployeeDB without the "Employee"-prefix: find(), fetch() and returnInstance() Using closures is good only when you really need to expand the scope of the function, and when that function will not be used by other methods. I find closures handy when I want to return function. I think that you will find that using closures generally decreases code reuse("Don't repeat yourself").

Categories : Python

Serializable on abstract base classes intended for JSF/CDI beans
If you do this, each class should have its own serialVersionUID (because it's private, it only belongs to that class). The rest of the question is really a coding standard question. My personal opinion is that serializable, as well as most other marker interfaces are just like any other interface. they handle polymorphism fine and you shouldn't need to redeclare the use of the interface. Understand that all you're doing is making them serializable. you're not enforcing any CDI scopes by doing this.

Categories : Java

Making abstract classes invisible; or: hiding my BananaHuman
You can use the EditorBrowsableAttribute and apply it to your class. This will make you class disappear from Intellisense if people are using your .dll. If you have your project referenced instead of the dll it will still be visible. Use like: [EditorBrowsable(EditorBrowsableState.Never)] public class BananaHuman { //.... } So if you would give me your .dll I wouldn't see BananaHuman pop up in Intellisense. But if I would inspect the Banana or Human class I would still see it inherited from BananaHuman because that IS the case. The EditorBrowsable attribute just makes it disappear from Intellisense, what is what you want.

Categories : C#

Abstract Base Classes versus Duck Typing
To me the mixins seem to be a main part of this module. Also in most cases, yes simple is the main goal to make perfect code, to me at least(not that I ever manage it). The fact that the ABC module's functions seem to be pretty clear about what they do, helps for sharing and skimming code. Finally, I may be wrong about this, so don't count on it, though I think some of ABC's functions can check for multiple attributes in one function.

Categories : Python

Memory allocation for override properties of abstract classes
A property does not (necessarily) imply storage is allocated. Properties are just syntactic sugar around get and set methods. Unless you also have a field to store the data, they are just pairs of methods. Example: If your base class has properties like this: public virtual int SomeProperty { get { return 0; } { set { } } Then no storage is allocated. But if you use an auto-property: public virtual int SomeProperty { get; set; } Then there is an automatic backing field generated, for which storage is allocated.

Categories : C#

should we always define interface and abstract classes, even when there will only be only 1 class extending them?
Abstract classes and interfaces are meant if you will use multiple of them. If you are only planning on one class, you don't need either. If at a later point you need two subclasses you could always convert your original class to an interface. One thing to keep in mind is that it is safe to write interfaces and abstract classes. If the functionality is already known and a skeleton has already been made, it is easier to test your classes and it will prevent errors.

Categories : Java

Java 8: virtual extension methods vs abstract class
abstract classes cannot be root classes of lambda expressions, while interfaces with virtual extension methods can be. also abstract classes can have constructors and member variables, while interfaces cannot. i believe its the execution of a possible constructor, and the possible throwing of a checked exception that prohibits abstract classes from being the root of a lambda expression. so if you want to write an API that allows the user to use lambda expressions, you should use interfaces instead.

Categories : Java

Can I use virtual abstract methods to inherit an interfaced object?
You can indeed do this. A virtual method, abstract or otherwise, can be used to meet an interface contract. You cannot declare the interface methods to be virtual or abstract. That makes little sense anyway because virtual and abstract are properties of implementation rather than interface. Finally, you don't need to declare the property again in the implementing object. Since I expect you'll only be referring to these objects via the interface, it makes little point repeating the property declaration. Here's a simple program to prove the point: {$APPTYPE CONSOLE} type IMyInterface = interface procedure Foo; end; TMyObject = class(TInterfacedObject, IMyInterface) private procedure Foo; virtual; abstract; end; TMyOtherObject = class(TMyObject) private proced

Categories : Delphi



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