Questions tagged [base-class]
In Object Oriented Programming, a base class is one from which other classes inherit. For example, a child-class `Male` and another child-class `Female` may both inherit from the base-class `Human`.
base-class
688
questions
1715
votes
42
answers
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views
What is the best way of implementing singleton in Python
This question is not for the discussion of whether or not the singleton design pattern is desirable, is an anti-pattern, or for any religious wars, but to discuss how this pattern is best implemented ...
- 21.6k
839
votes
38
answers
201k
views
Interface vs Base class
When should I use an interface and when should I use a base class?
Should it always be an interface if I don't want to actually define a base implementation of the methods?
If I have a Dog and Cat ...
169
votes
11
answers
283k
views
Does delete on a pointer to a subclass call the base class destructor?
I have an class A which uses a heap memory allocation for one of its fields. Class A is instantiated and stored as a pointer field in another class (class B.
When I'm done with an object of class B, ...
- 39.1k
138
votes
8
answers
63k
views
C# Class naming convention: Is it BaseClass or ClassBase or AbstractClass
What is the recommended approach to naming base classes? Is it prefixing the type name with "Base" or "Abstract" or would we just suffix it with "Base"?
Consider the following:
type: ViewModel e.g. ...
- 18.8k
137
votes
7
answers
98k
views
Will the base class constructor be automatically called?
class Person
{
public int age;
public Person()
{
age = 1;
}
}
class Customer : Person
{
public Customer()
{
age += 1;
}
}
Customer customer = new Customer(...
- 1,900
119
votes
33
answers
163k
views
Is it possible to assign a base class object to a derived class reference with an explicit typecast?
Is it possible to assign a base class object to a derived class reference with an explicit typecast in C#?.
I have tried it and it creates a run-time error.
- 6,747
90
votes
6
answers
13k
views
Why is there no universal base class in C++?
From a design point of view, why is that, in C++, there is no mother-of-all base-class, what's usually object in other languages?
- 76k
79
votes
10
answers
127k
views
How to hide an inherited property in a class without modifying the inherited class (base class)?
If i have the following code example:
public class ClassBase
{
public int ID { get; set; }
public string Name { get; set; }
}
public class ClassA : ClassBase
{
public int JustNumber { ...
- 6,066
64
votes
9
answers
71k
views
Cast base class to derived class python (or more pythonic way of extending classes)
I need to extend the Networkx python package and add a few methods to the Graph class for my particular need
The way I thought about doing this is simplying deriving a new class say NewGraph, and ...
- 9,136
60
votes
7
answers
56k
views
how to get derived class name from base class
I have a base class Person and derived classes Manager and Employee. Now, what I would like to know is the object created is Manager or the Employee.
The person is given as belows:
from Project....
- 5,102
37
votes
5
answers
8k
views
GCC issue: using a member of a base class that depends on a template argument
The following code doesn't compile with gcc, but does with Visual Studio:
template <typename T> class A {
public:
T foo;
};
template <typename T> class B: public A <T> {
public:
...
- 33.7k
36
votes
3
answers
81k
views
How to resolve "pure virtual method called"
I understand why this is happening, but I'm stuck trying to resolve it...here is what my code is doing when the error is generated (thus, leading to a crash) when my program exits...
pure virtual ...
- 819
36
votes
2
answers
20k
views
How to avoid error "Constructor on type 'MyType' not found" when inheriting a base class
I have a Visual Studio 2010 Windows Forms app which includes a Form base class that other classes will inherit. The base class' constructor takes a parameter that the child classes will pass to the ...
- 10.8k
34
votes
1
answer
42k
views
conversion to inaccessible base class is not allowed [duplicate]
I define a class B1 and a derived class D1 at first. Then I want to define a reference to B1 and initialize that to the D1 object I just defined. Here comes the error, saying that "conversion to ...
- 459
34
votes
9
answers
34k
views
.NET: Unable to cast object to interface it implements
I have a class (TabControlH60) that both inherits from a base class (UserControl) and implements an interface (IFrameworkClient). I instantiate the object using the .NET Activator class. With the ...
- 361
34
votes
8
answers
22k
views
How to call an explicitly implemented interface-method on the base class
I have a situation, where two classes (one deriving from the other) both implement the same interface explicitly:
interface I
{
int M();
}
class A : I
{
int I.M() { return 1; }
}
class B : A, I
...
- 96k
28
votes
4
answers
24k
views
Why use base class pointers for derived classes
class base{
.....
virtual void function1();
virtual void function2();
};
class derived::public base{
int function1();
int function2();
};
int main()
{
derived d;
base *b =...
- 349
28
votes
3
answers
10k
views
ExecuteCore() in base class not fired in MVC 4 beta
I have a base controller class:
And all my other controller inherits this BaseClass like this
All this works great in MVC3 (test again today, it really works) but it seems that the ExecuteCore in ...
- 458
28
votes
5
answers
12k
views
In .NET, can you use reflection to get all non-inherited methods of a class?
Because of this issue here, I'm trying to write a custom JsonConverter that handles cases where you subclass a list or a collection, then add extra properties to it. As such, one approach would be to ...
- 29.8k
27
votes
10
answers
18k
views
What are good candidates for base controller class in ASP.NET MVC?
I've seen a lot of people talk about using base controllers in their ASP.NET MVC projects. The typical examples I've seen do this for logging or maybe CRUD scaffolding. What are some other good uses ...
- 29k
27
votes
2
answers
7k
views
Non-testable base class extending PHPUnit_Framework_TestCase
Summary
How can I create a base class that extends PHPUnit_Framework_TestCase and use that for subclassing actual test cases, without having the base class itself tested by PHPUnit?
Further ...
- 1,635
27
votes
3
answers
15k
views
Can you extend the default JsonConverter used in JSON.NET for collections?
I'm trying to write a custom JsonConverter for cases where a person subclasses a list or collection, but then adds extra properties to the subclass (see here). The current implementation of JSON.NET ...
- 29.8k
26
votes
2
answers
38k
views
How do derived class constructors work in python?
I have the following base class:
class NeuralNetworkBase:
def __init__(self, numberOfInputs, numberOfHiddenNeurons, numberOfOutputs):
self.inputLayer = numpy.zeros(shape = (numberOfInputs)...
- 104k
26
votes
2
answers
26k
views
How can I polymorphic deserialization Json String using Java and Jackson Library?
I've some classes A, B, C they all inherit from class BaseClass.
I've a String json that contains the json representation of the A, B, C or BaseClass.
I want to have some way to deserialize this ...
- 7,180
25
votes
2
answers
13k
views
Android: Call super() at the beginning or end of onStart(), onStop(), onDestroy() in activity?
Where in onStart(), onStop(), onDestroy() of an activity do I call super.onStart(), super.onStop(), super.onDestroy() ?
- 4,631
24
votes
2
answers
52k
views
Abstract base class in Dart
I have been programming in Java for nearly two years but I am now more shifting to web programming and thus to Javascript, or in my case to Dart. For a project I'm working on I would like to have ...
- 1,208
24
votes
2
answers
54k
views
How do I call a derived class method from the base class?
I have read several similar questions about this but none seem to solve the problem I am facing. The typical answer is to cast as the derived class but I cannot since I do not know the derived class ...
- 1,406
21
votes
2
answers
4k
views
Why is a base class in C# allowed to implement an interface contract without inheriting from it?
I've stumbled upon this "feature" of C# - the base class that implements interface methods does not have to derive from it.
Example:
public interface IContract
{
void Func();
}
// Note that ...
- 329
20
votes
2
answers
621
views
Name lookup differences between g++ and MSVS
Consider this code:
#include <iostream>
namespace N {
class A {};
void f(A a) { std::cout << "N::f\n"; }
}
void f(int i) { std::cout << "::f\n"; }
template <typename T&...
- 5,744
20
votes
5
answers
9k
views
Do you have a common base class for Hibernate entities?
Do you have a common base class for Hibernate entities, i.e. a MappedSuperclass with id, version and other common properties? Are there any drawbacks?
Example:
@MappedSuperclass()
public class ...
- 20.1k
19
votes
5
answers
26k
views
Calling a constructor of the base class from a subclass' constructor body
I was under impression that it's impossible, see for example:
Calling the constructor of the base class after some other instructions in C++
But the following program runs and produces two lines of "...
- 1,884
18
votes
7
answers
52k
views
How to Get Base Class Instance from a Derived Class
I don't know if this is possible, but I am trying to get the Base Class instance from a Derived Class. In C#, I can use the base keyword to access properties and methods of the Base Class (of course), ...
- 529
18
votes
4
answers
14k
views
C# private (hidden) base class
Is it possible to make a C# base class accessible only within the library assembly it's compiled into, while making other subclasses that inherit from it public?
For example:
using System.IO;
class ...
- 12.1k
16
votes
2
answers
11k
views
Understanding virtual base classes and constructor calls
I'm a bit confused about how virtual base classes work. In particular, I was wondering how the constructor of the base class gets called. I wrote an example to understand it:
#include <cstdio>...
- 10.5k
16
votes
2
answers
26k
views
Python inheritance - calling base class methods inside child class?
It baffles me how I can't find a clear explanation of this anywhere.
Why and when do you need to call the method of the base class inside the same-name method of the child class?
class Child(Base):
...
- 161
14
votes
5
answers
4k
views
C++ template duck-typing vs pure virtual base class inheritance
Which are the guidelines for choosing between template duck-typing and pure virtual base class inheritance? Examples:
// templates
class duck {
void sing() { std::cout << "quack\n"; }
};
...
- 9,070
14
votes
1
answer
794
views
Scala: How can I make my immutable classes easier to subclass?
I've recently created an immutable class supporting operations like +, -, etc. that returns a new instance of that class when it is changed.
I wanted to make a subclass of that class to add a bit of ...
- 8,720
14
votes
7
answers
6k
views
Compiler warning at C++ template base class
I get a compiler warning, that I don't understand in that context. When I compile the "Child.cpp" from the following code. (Don't wonder: I stripped off my class declarations to the bare minimum, so ...
- 141
13
votes
1
answer
311
views
Why does the compiler select the base class constructor inside the template argument list?
Follow-up question to this one.
Basically, in the following code, why does the compiler think that the B inside A<B> in Cs constructor refer to the (inaccessible) constructor of the B base ...
- 131k
13
votes
3
answers
36k
views
C++: Accessing parent methods and variables
In which way should I access this parent method and parent variable?
class Base
{
public:
std::string mWords;
Base() { mWords = "blahblahblah" }
};
class Foundation
{
public:
Write( std::...
user542687
12
votes
5
answers
7k
views
Call a C++ base class method automatically
I'm trying to implement the command design pattern, but I'm stumbling accross a conceptual problem. Let's say you have a base class and a few subclasses like in the example below:
class Command : ...
- 2,223
12
votes
5
answers
11k
views
C# protected members accessed via base class variable [duplicate]
It may seems rather newbie question, but can you explain why method Der.B() cannot access protected Foo via Base class variable? This looks weird to me:
public class Base
{
protected int Foo;
}
...
- 4,581
12
votes
2
answers
18k
views
Call derived class method from base class reference
class Material
{
public:
void foo()
{
cout << "Class Material";
}
};
class Unusual_Material : public Material
{
public:
void foo()
{
cout << "Class Unusual_Material";
}
};
int ...
- 918
12
votes
5
answers
13k
views
C# "Rename" Property in Derived Class
When you read this you'll be awfully tempted to give advice like "this is a bad idea for the following reason..."
Bear with me. I know there are other ways to approach this. This question should be ...
- 9,147
11
votes
3
answers
14k
views
Order of calling base class constructor from derived class initialization list
struct B {
int b1, b2;
B(int, int);
};
struct D : B {
int d1, d2;
// which is technically better ?
D (int i, int j, int k, int l) : B(i,j), d1(k), d2(l) {} // 1st Base
// or
D (int i, ...
- 69.4k
11
votes
4
answers
16k
views
c++ casting base class to derived class mess
If I were to create a base class called base and derived classes called derived_1, derived_2 etc... I use a collection of instances of the base class, then when I retrieved an element and tried to use ...
- 3,289
10
votes
4
answers
35k
views
What is the difference between a simple base class and abstract class?
I was doing a kind of R&D and am confused with the concept of an abstract class.
What I know about an abstract class is that it may contain concrete methods, and it may contain virtual methods. ...
- 8,538
10
votes
3
answers
10k
views
Is it possible a class to inherit only some(not all) base class members?
Is there a way that a derived class could inherit only a few of all the base class members..in C#?
If such maneuver is possible, please provide some example code.
- 147
10
votes
3
answers
7k
views
Use selenium webdriver as a baseclass python
I searched for a while for this one and was surprised i couldn't find anything, maybe because it's simple. I've been programming in python for about 3 months doing automated testing with selenium ...
- 336
10
votes
1
answer
3k
views
Angular 2 Base Class Output EventEmitter doesn't get raised or handled
Very simple base class Closer
import {EventEmitter, Output} from 'angular2/core';
export class Closer {
@Output() closed: EventEmitter<any> = new EventEmitter();
constructor() {}
close(...
- 2,031