inheritance

问题 I have a class.I have extended Fragment to this class because I used fragments when developing Navigation Drawer. The code is below public class aboutSLFragment extends Fragment { public aboutSLFragment() { // Required empty public constructor } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // Inflate the layout for this fragment return inflater.inflate(R.layout.fragment_about_sl, container, false); } @Override public void

问题 I have one IIFE content which looks like this: var A = (function() { var method1 = function() { alert("PARENT METHOD"); } var method2 = function() { method1(); } return { method1: method1, method2: method2 } })(); I want to override this method1 in another javascript object in a way when this method2 executes then it will call the overriden method1, not this original method1. Thanks in advance. 回答1: You are going to need to use prototype in order to accomplish this the way you would like.

问题 Javascript lacks a class construct, however you can still achieve inheritance many different ways. You can mimic classes by utilizing prototypes to create constructor functions and thus implementing inheritance via delegation. The most common way to do this is with the new keyword, but you can also implement object.create() . Alternatively, you can take a concatenative approach and copy behavior that you want your object to inherit directly into the object itself, rather than by pointing its

问题 Chapter 16.4 Parameterized Virtuality in the C++ Templates - The Complete Guide , by David Vandevoorde and Nicolai M. Josuttis, says: C++ allows us to parameterize directly three kinds of entities through templates: types, constants ("nontypes"), and templates. However, indirectly, it also allows us to parameterize other attributes such as the virtuality of a member function. The following code was illustrated in that chapter: #include <iostream> struct NotVirtual {}; struct IsVirtual {

问题 Chapter 16.4 Parameterized Virtuality in the C++ Templates - The Complete Guide , by David Vandevoorde and Nicolai M. Josuttis, says: C++ allows us to parameterize directly three kinds of entities through templates: types, constants ("nontypes"), and templates. However, indirectly, it also allows us to parameterize other attributes such as the virtuality of a member function. The following code was illustrated in that chapter: #include <iostream> struct NotVirtual {}; struct IsVirtual {

问题 I have the following python code: class Meta(type): def __call__(cls, *args, **kwargs): obj = type.__call__(cls, *args, **kwargs) # Only do checks for subclasses if cls.__name__ == 'Parent': return obj required_attrs = ['x'] for ra in required_attrs: if ra not in dir(obj): fmt = 'Subclasses of Parent must define the %s attribute' raise NotImplementedError(fmt % ra) return obj class Parent(metaclass=Meta): pass class Child(Parent): def __init__(self): self.x = True Meta is used only to require

问题 I have the following python code: class Meta(type): def __call__(cls, *args, **kwargs): obj = type.__call__(cls, *args, **kwargs) # Only do checks for subclasses if cls.__name__ == 'Parent': return obj required_attrs = ['x'] for ra in required_attrs: if ra not in dir(obj): fmt = 'Subclasses of Parent must define the %s attribute' raise NotImplementedError(fmt % ra) return obj class Parent(metaclass=Meta): pass class Child(Parent): def __init__(self): self.x = True Meta is used only to require

问题 I have created a custom abstract class, which in turn of course derived classes were also created. public abstract class AbstractBaseClass ... public class ChildClass1 : AbstractBaseClass ... Now, whenever I declare for example AbstractBaseClass baseClass = null , and wherever null checks follow after this initialization, it always fails. if (baseClass == null) { // this block is never reached - condition always evaluates to false // let's say AbstractBaseClass baseClass = null is at line 10

问题 Help, I have this class var jMath = { pi2: Math.PI, foo: function() { return this.pi2; } } I want to make the pi2 constant and i want jMath to inherit from Math object. How do I do that? 回答1: Oh amusing, scratch all that, this is the correct version: function JMath() { this.foo = function() { return this.PI; } } JMath.prototype = Math; var jMath = new JMath(); alert(jMath.foo()); (which matches what the other answer is here) (I originally tried to set the prototype using "JMath.prototype =

问题 So, I'm trying to figure out the best (most elegant with the least amount of code) way to allow overriding specific functions of a property (e.g., just the getter, just the setter, etc.) in python. I'm a fan of the following way of doing properties, due to the fact that all of their methods are encapsulated in the same indented block of code (it's easier to see where the functions dealing with one property stop and the functions dealing with the next begin): @apply def foo(): """A foobar"""