overriding

Why not override instead of using abstract class?

由 ▼魔方 西西 提交于 2019-12-04 01:36:47
问题 This might be a simple question for many but has confused me. I am picking an example from Kathy Sierra that shows the utility of Abstract Classes but I am unable to understand the overall importance of abstract classes. Example We have an abstract class Car with abstract methods - power() & topSpeed() . These methods are implemented in sub classes BMW , Volkswagen and Audi . My question is - why do we need to have the abstract class Car in the first place to customize methods for each car

Scala : Why can't we do super.val?

由 巧了我就是萌 提交于 2019-12-04 01:24:34
问题 I am practicing this code from JavaTpoint for learning inheritance in Scala. But I cannot access the member Bike from the class Vehicle who's value is initialized to zero. I tried by super type reference but it still shows the overridden value. Why does it not allow to access the super class field and directs to the overridden sub class field (speed) . here is the code and the output. Thanking in advance. class Vehicle { val speed = 0 println("In vehicle constructor " +speed) def run() {

Ruby Class Methods vs. Methods in Eigenclasses

由 自古美人都是妖i 提交于 2019-12-04 01:23:37
Are class methods and methods in the eigenclass (or metaclass) of that class just two ways to define one thing? Otherwise, what are the differences? class X # class method def self.a "a" end # eigenclass method class << self def b "b" end end end Do X.a and X.b behave differently in any way? I recognize that I can overwrite or alias class methods by opening the eigenclass: irb(main):031:0> class X; def self.a; "a"; end; end => nil irb(main):032:0> class X; class << self; alias_method :b, :a; end; end => #<Class:X> irb(main):033:0> X.a => "a" irb(main):034:0> X.b => "a" irb(main):035:0> class X

Why do not call overridable methods in constructors?

由 时光总嘲笑我的痴心妄想 提交于 2019-12-04 00:34:34
问题 This is an oversimplified example, but I have some real-life code that conceptually does the same thing (trying to validate values "set" accessor methods of derivative classes), and the Analyzer gives me "Do not call overridable methods in constructors." I'm trying to figure out if I should change my code, or ignore the warning. I can't think of any reason I should heed the warning. public abstract class SimpleUrl { protected string _url; public abstract string Url { get; set; } public

jquery override event

由 折月煮酒 提交于 2019-12-03 23:55:25
问题 I have an anchor like this <a href='#' onclick='return showform(this)'>click me</a> But I want to be able to override the onclick function, how to do this in jquery? because it seems when I add $('a').click( function() { alert('hi there!'); } ); the new click handler is not overriding the old one 回答1: Have you tried something like this: $("a").removeAttr("onclick"); 回答2: In your case the onCick event is overriding the jQuery one. What you might be able to do is: $('a').unbind('click').click

PHP - override function with different number of parameters

由 感情迁移 提交于 2019-12-03 23:43:18
问题 I'm extending a class, but in some scenarios I'm overriding a method. Sometimes in 2 parameters, sometimes in 3, sometimes without parameters. Unfortunately I'm getting a PHP warning. My minimum verifiable example: http://pastebin.com/6MqUX9Ui <?php class first { public function something($param1) { return 'first-'.$param1; } } class second extends first { public function something($param1, $param2) { return 'second params=('.$param1.','.$param2.')'; } } // Strict standards: Declaration of

C# Can a base class property be invoked from derived class

由 假如想象 提交于 2019-12-03 22:58:17
I have a base class with a property which has a setter method. Is there a way to invoke the setter in the base class from a derived class and add some more functionality to it just like we do with overriden methods using the base keyword. Sorry I should have added an example. Here is an example. Hope I get it right: public class A { public abstract void AProperty { set { // doing something here } } } public class B : A { public override void AProperty { set { // how to invoke the base class setter here // then add some more stuff here } } } EDIT : the revised example should demostrate the

overriding methods without subclassing in Java

由 别说谁变了你拦得住时间么 提交于 2019-12-03 19:56:27
问题 I started on a new project recently and saw the usage of overriding like below for the first time. public class SomeClass { public void myMethod() { XStream xstream = new XStream() { @Override protected MapperWrapper wrapMapper(MapperWrapper next) { return new MapperWrapper(next) { // the rest ommitted Basically, it's overriding the wrapMapper() method of the XStream class in the thoughtworks xstream api but without having SomeClass to extend the XStream class. I've worked with Java for a

Equivalent of Java interfaces in C++? [duplicate]

由 不羁的心 提交于 2019-12-03 19:48:02
问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: How do you declare an interface in C++? Interface as in java in c++? I am a Java programmer learning C++, and I was wondering if there is something like Java interfaces in C++, i.e. classes that another class can implement/extend more than one of. Thanks. p.s. New here so tell me if I did anything wrong. 回答1: In C++ a class containing only pure virtual methods denotes an interface. Example: // Define the

Why can final constants in Java be overridden?

由 若如初见. 提交于 2019-12-03 18:57:15
问题 Consider the following interface in Java: public interface I { public final String KEY = "a"; } And the following class: public class A implements I { public String KEY = "b"; public String getKey() { return KEY; } } Why is it possible for class A to come along and override interface I's final constant? Try for yourself: A a = new A(); String s = a.getKey(); // returns "b"!!! 回答1: Despite the fact that you are shadowing the variable it's quite interesting to know that you can change final
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