I need to have a class constructor in PHP call its parent’s parent’s (grandparent?) constructor without calling the parent constructor. // main class that everything inherits class Grandpa { public function __construct() { } } class Papa extends Grandpa { public function __construct() { // call Grandpa’s constructor parent::__construct(); } } class Kiddo extends Papa … Read more
This question already has answers here: A Base Class pointer can point to a derived class object. Why is the vice-versa not true? (13 answers) Closed 7 years ago. I’m a newbie to Java programming, trying to get the hang of OOP. So I built this abstract class: public abstract class Vehicle{….} and 2 subclasses: … Read more
One of the major advantages with Javascript is said to be that it is a prototype based language. But what does it mean that Javascript is prototype based, and why is that an advantage? 8 Answers 8
This question already has answers here: Is it possible to make abstract classes in Python? (13 answers) Closed 3 years ago. I am having trouble in using inheritance with Python. While the concept seems too easy for me in Java yet up till now I have been unable to understand in Python which is surprising … Read more
This is an interview question. Does subclasses inherit private fields? I answered “No”, because we can’t access them using the “normal OOP way”. But the interviewer thinks that they are inherited, because we can access such fields indirectly or using reflection and they still exist in the object. After I came back, I found the … Read more
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__() … Read more
Data classes seem to be the replacement to the old-fashioned POJOs in Java. It is quite expectable that these classes would allow for inheritance, but I can see no convenient way to extend a data class. What I need is something like this: open data class Resource (var id: Long = 0, var location: String … Read more
Why does this code: class A { public: explicit A(int x) {} }; class B: public A { }; int main(void) { B *b = new B(5); delete b; } Result in these errors: main.cpp: In function ‘int main()’: main.cpp:13: error: no matching function for call to ‘B::B(int)’ main.cpp:8: note: candidates are: B::B() main.cpp:8: note: … Read more
I’m trying to define my own exception class the easiest way, and this is what I’m getting: public class MyException extends Exception {} public class Foo { public bar() throws MyException { throw new MyException(“try again please”); } } This is what Java compiler says: cannot find symbol: constructor MyException(java.lang.String) I had a feeling that … Read more
So I finally stopped dragging my feet all these years and decided to learn JavaScript “properly”. One of the most head-scratching elements of the languages design is its implementation of inheritance. Having experience in Ruby, I was really happy to see closures and dynamic typing; but for the life of me can’t figure out what … Read more
