inheritance

问题 Say I have a multiple inheritance scenario: class A(object): # code for A here class B(object): # code for B here class C(A, B): def __init__(self): # What's the right code to write here to ensure # A.__init__ and B.__init__ get called? There's two typical approaches to writing C 's __init__ : (old-style) ParentClass.__init__(self) (newer-style) super(DerivedClass, self).__init__() However, in either case, if the parent classes ( A and B ) don't follow the same convention, then the code will

问题 I know : indicates inheritance in C#; but what does it mean when the same identifier is on either side? Eg class GameObject : GameObject { 回答1: It does not work, because Visual Studio will throw a 'cyclic dependency' error, because, when you think about it, GameObject inherits from GameObject which inherits from GameObject which inherits from... In other words, this is impossible, and so means nothing (except, like Neil mentioned in the comments, a compiler error). 回答2: Or this is Unicode

问题 I received homework to make program without casting using constructors so this is my code, I have two classes: class Base { protected: int var; public: Base(int var = 0); Base(const Base&); Base& operator=(const Base&); virtual ~Base(){}; virtual void foo(); void foo() const; operator int(); }; class Derived: public Base { public: Derived(int var): Base(var){}; Derived(const Base&); Derived& Derived::operator=(const Base& base); ~Derived(){}; virtual void foo(); }; here two of my functions of

问题 I am new to COM and c# and I would like to add functionality to a COM object that is exposed by a third-party program. Initially my intention was to inherit from the COM object class, but I found out it was not so straight forward (for example here). Presently, I have two interfaces (namely IComAuto and ComAuto ) and an associated class ( ComAutoClass ). To add my custom methods to ComAuto objects, I have created a class ComObjectWrapper that inherits from this interface and implements it by

问题 I am trying to Iterate directories in Perl, getting introspectable objects as result, mostly so I can print fields like mtime when I'm using Dumper on the returns from IO::All . I have discovered, that it can be done, if in the module IO::All::File (for me, /usr/local/share/perl/5.10.1/IO/All/File.pm ), I add the line field mtimef => undef; , and then modify its sub file so it runs $self->mtimef($self->mtime); (note, this field cannot have the same name ( mtime ) as the corresponding method

问题 This is an example from "Effective Python", that I am clearly missing something on. I added a few print's to help convince myself, but I'm still a little unclear. I understand that when you attempt to access an inherited private variable, it fails because in the instance dictionary of the child, the name has been mangled (last line below, attempting to access a.__value rightfully fails because the instance dict contains the mangled version _ApiClass__value ). Where I'm getting tripped up is

问题 This is an example from "Effective Python", that I am clearly missing something on. I added a few print's to help convince myself, but I'm still a little unclear. I understand that when you attempt to access an inherited private variable, it fails because in the instance dictionary of the child, the name has been mangled (last line below, attempting to access a.__value rightfully fails because the instance dict contains the mangled version _ApiClass__value ). Where I'm getting tripped up is

问题 I am using a parent class in my app to provide some basic functionality to its children. It looks roughly like this: class Base { constructor(stream) { stream.subscribe(this.onData) } onData(data) { throw new Error('"onData" method must be implemented') } } class Child extends Base { onData(data) { // do stuff... } } That works fine and when I instantiate the Child , Base passes Child.onData to the stream The only problem is scope. In Child.onData I make a heavy use of other methods defined

问题 dir/ | |___ __init__.py | |___ Base_class.py | |___ Subclass.py __init__.py is empty(as mentioned here) /* Base_class.py class Employee: numOfEmployees = 0 # Pure class member, no need to override raiseAmount = 1.04 # Could not be pure class member, so, can it be overidden by object? # Yes. make sense # This is why we use self.raiseAmount in methods def __init__(self, firstName, lastName, pay): self.firstName = firstName self.lastName = lastName self.pay = pay self.email = firstName + '.' +

问题 class parents{ public $a; function __construct(){ echo $this->a; } } class child extends parents{ function __construct(){ $this->a = 1; parent::__construct(); } } $new = new child();//print 1 This code above print 1,which means whenever we create an instance of a child class,and assign value to properties inherited from its parent,the property in its parent class also has been assigned.But the code below shows different: class parents{ public $a; function test(){ $child = new child(); echo