overriding

问题 I know that I can use the sealed in order to prevent other classes to inherit a certain class, but is it possible to allow inheritance but prevent overriding of some virtual methods? 回答1: Only virtual methods can be overridden. Just leave out virtual , and your method will not be overridable. 回答2: you can also use sealed modifier to prevent a derived class from further overriding the method. check this out: Sealed methods 回答3: Yes. The sealed keyword can also be used on methods, to indicate

问题 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

问题 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

问题 I have a annoying problem with @Override annotations in Eclipse. Often when i import working projects on a new PC, Eclipse marks some of the @Override annotations as wrong. If i remove the annotations everything is fine and Eclipse also indicates that the methods are overriding the parents methods but adding the Override annotation causes the error again. I am currently working on an Android project so it might be a problem with Android and not with Eclipse.. 回答1: This is most likely because

问题 Consider the following code: public interface A { public A another(); } public interface B { public B another(); } public interface AB extends A,B { public AB another(); } This leads to a compile error on AB : types B and A are incompatible; both define another(), but with unrelated return types I've seen this SO question, and follow the incompatibility example in the the accepted answer - i.e. public interface C { public void doSomething(); } public interface D { public boolean doSomething()

问题 Yesterday I posted a question about the new/virtual/override keywords, and i learned a lot from your answers. But still i remain with some doubts. In between all the "boxes", i lost touch with what's really happening to the type's method tables. For instance: interface I1 { void Draw(); } interface I2 { void Draw(); } class A : I1, I2 { public void Minstance() { Console.WriteLine("A::MInstance"); } public virtual void Draw() { Console.WriteLine("A::Draw"); } void I2.Draw() { Console.WriteLine

问题 After having read Ian Boyd's constructor series questions (1, 2, 3, 4), I realize I don't quite grasp the literal meaning on what's being hidden. I know (correct me if I'm wrong) override 's sole purpose is to be able to have polymorphic behavior, so that run-time can resolve a method depending on the actual type of an instance - as opposed to the declared type. Consider the following code: type TBase = class procedure Proc1; virtual; procedure Proc2; virtual; end; TChild = class(TBase)

问题 I want to specifically set a field when a user is created. I have class RegistrationsController < Devise::RegistrationsController def create super @user.tag_list = params[:tags] end end I have check boxes that pass the tags parameter and I have verified in the server logs that the tags parameter is being passed. However, when I call @user.tag_list in the console I just get a blank response [] . I feel that the problem lies in my manipulating of the create method of devise. I have not

问题 Is there a reason one can change the access modifier of an overridden method? For instance, abstract class Foo{ void start(){...} } And then change the package-private access modifier to public , final class Bar extends Foo{ @Override public void start(){...} } I'm just asking this question out of curiosity. 回答1: Java doesn't let you make the access modifier more restrictive , because that would violate the rule that a subclass instance should be useable in place of a superclass instance. But

问题 I have rewritten and stand-alone tested the behaviour of an inner function invoked by one of the Emacs functions bundled with Emacs 24. What is the preferred way of incorporating - e.g. in my init.el - my function's behaviour overriding the bundled function? I have followed various threads of advice vs fset etc. and am confused. 回答1: @iainH You tend to get to a useful answer faster by describing what goal you're trying to accomplish, then what you have so far. I asked for code to try to help