overriding

When NOT to call super() method when overriding?

由 此生再无相见时 提交于 2019-11-26 23:54:53
问题 When I make my own Android custom class, I extend its native class. Then when I want to override the base method, I always call super() method, just like I always do in onCreate , onStop , etc. And I thought this is it, as from the very beginning Android team advised us to always call super on every method override. But, in many books I can see that developers, more experienced than myself, often omit calling super and I really doubt they do it as a lack of knowledge. For example, look at

Can I override and overload static methods in Java?

由 半城伤御伤魂 提交于 2019-11-26 23:38:30
I'd like to know: Why can't static methods be overridden in Java? Can static methods be overloaded in Java? opensas Static methods can not be overridden in the exact sense of the word, but they can hide parent static methods In practice it means that tue compiler will decide which method to execute at compile time, and not at runtime, as it does with overridden instance methods. For a neat example have a look here . And this is java documentation explaining the difference between overriding instance methods and hiding class (static) methods. Overriding: Overriding in Java simply means that the

Java abstract class fields override

由 ☆樱花仙子☆ 提交于 2019-11-26 23:21:08
问题 I have an abstract class that should implement a public field, this field is an interface or another abstract classe. something like this: public abstract class GenericContainer { public GenericChild child; } public abstract class GenericChild { public int prop1=1; } public abstract class SpecialChild extend GenericChild { public int prop1=2; } Now i have another specialized class Container: public abstract class SpecialContainer extends GenericContainer { public SpecialChild child=new

Android - onBackPressed() not working

由 与世无争的帅哥 提交于 2019-11-26 23:02:25
I have an application building against Android 2.1 and I want to override the back button. I have followed the example here: http://android-developers.blogspot.com/2009_12_01_archive.html And my code is as follows: @Override public boolean onKeyDown(int keyCode, KeyEvent event) { if (Integer.parseInt(android.os.Build.VERSION.SDK) < 5 && keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) { Log.d("CDA", "onKeyDown Called"); onBackPressed(); } return true; } @Override public void onBackPressed() { Log.d("CDA", "onBackPressed Called"); Intent setIntent = new Intent(Intent.ACTION_MAIN

How can I define a custom equality operation that will be used by immutable Set comparison methods

由 别来无恙 提交于 2019-11-26 22:52:29
问题 I have an immutable Set of a class, Set[MyClass], and I want to use the Set methods intersect and diff, but I want them to test for equality using my custom equals method, rather than default object equality test I have tried overriding the == operator, but it isn't being used. Thanks in advance. Edit: The intersect method is a concrete value member of GenSetLike spec: http://www.scala-lang.org/api/current/scala/collection/GenSetLike.html src: https://lampsvn.epfl.ch/trac/scala/browser/scala

Rails: Overriding ActiveRecord association method

由 我只是一个虾纸丫 提交于 2019-11-26 22:45:27
问题 Is there a way to override one of the methods provided by an ActiveRecord association? Say for example I have the following typical polymorphic has_many :through association: class Story < ActiveRecord::Base has_many :taggings, :as => :taggable has_many :tags, :through => :taggings, :order => :name end class Tag < ActiveRecord::Base has_many :taggings, :dependent => :destroy has_many :stories, :through => :taggings, :source => :taggable, :source_type => "Story" end As you probably know this

Force a class to override the .equals method

由 …衆ロ難τιáo~ 提交于 2019-11-26 22:42:46
问题 I have a bunch of class who implement a common interface : Command. And this bunch of class goes to a Map. To get the Map working correctly, I need to each class who implements Command to override the Object.equals(Object other) method. it's fine. But i whould like to force the overriding of equals. => Have a compilation error when something who implement command dont override equals. It's that possible ? Edit : BTW , i will also need to forcing the override of hashcode... 回答1: No, you can't.

Inheritance and method overloading

由 不打扰是莪最后的温柔 提交于 2019-11-26 22:41:14
Why C++ compiler gives this error? Why i can access lol() from B, but can not access rofl() [without parameters]. Where is the catch? class A { public: void lol(void) {} void rofl(void) { return rofl(0);} virtual void rofl(int x) {} }; class B : public A { public: virtual void rofl(int x) {} }; int _tmain(int argc, _TCHAR* argv[]) { A a; a.lol(); a.rofl(1); a.rofl(); B b; b.lol(); b.rofl(1); b.rofl(); //ERROR -> B::rofl function does not take 0 arguments return 0; } The B::rofl(int) 'hides' the A::rofl() . In order to have A 's rofl overloads, you should declare B to be using A::rofl; . class

Override function (e.g. “alert”) and call the original function?

由 删除回忆录丶 提交于 2019-11-26 22:40:29
I would like to override a Javascript built-in function with a new version that calls the original (similarly to overriding a method on a class with a version that calls super in many languages). How can I do this? For example... window.alert = function(str) { //do something additional if(console) console.log(str); //super.alert(str) // How do I do this bit? } Store a reference to the original function in a variable: (function() { var _alert = window.alert; // <-- Reference window.alert = function(str) { // do something additional if(console) console.log(str); //return _alert.apply(this,

Overriding vs Virtual

由 点点圈 提交于 2019-11-26 22:39:28
问题 What is the purpose of using the reserved word virtual in front of functions? If I want a child class to override a parent function, I just declare the same function such as void draw(){} . class Parent { public: void say() { std::cout << "1"; } }; class Child : public Parent { public: void say() { std::cout << "2"; } }; int main() { Child* a = new Child(); a->say(); return 0; } The output is 2. So again, why would the reserved word virtual be necessary in the header of say() ? Thanks a bunch
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