Questions tagged [virtual-functions]
The virtual-functions tag has no usage guidance.
22
questions
2
votes
3
answers
316
views
Why do we need factories in the first place?
I went through various blogs but nowhere I can find the reason of having virtual constructors in C++.
Why is virtual constructor needed and lets say if we go through the wrong way of creating virtual ...
- 31
2
votes
3
answers
324
views
Object Oriented Programming - what is the best way to add new parameters?
I have a doubt about what would be the right OOP approach for implementing classes that do similar stuff with different parameters.
To provide a simple example, I would use two polynomial classes, ...
- 138
-1
votes
1
answer
76
views
What do you call a function that properly remains undefined?
Backstory:
I have subclasses that are supposed to override and define various functions, but not neccessarily all of them. They can't remain purely virtual though for obvious reasons, and so I am ...
- 3,593
3
votes
3
answers
2k
views
True cost of virtual dispatch in C++ - when stop using it?
What I've learned so far as a programmer has lead me to think that the easiest way to write large scale software is to use a lot of interfaces - this makes things very easy to isolate and test. In ...
- 207
0
votes
1
answer
90
views
How to define values dependant on the derived type?
My base class must provide an interface to get a value that is dependent solely on the type of the derived class. I can think of two ways of implementing this:
Solution A, virtual functions:
class ...
- 111
23
votes
4
answers
6k
views
Never make public members virtual/abstract - really?
Back in the 2000s a colleague of mine told me that it is an anti-pattern to make public methods virtual or abstract.
For example, he considered a class like this not well designed:
public abstract ...
- 389
7
votes
2
answers
3k
views
C++ : What is the order of function pointers inside vtable?
In this answer to "In C++ why and how are virtual functions slower?",
the author mentions below point:
"Get the right function address from the vtable into a register (the index where the correct ...
1
vote
1
answer
256
views
Differences between branching and virtual methods
I was trying to find more info on the matter but could only find this:
In C++ why and how are virtual functions slower?
The answer says that the virtual call "Get[s] the right function address from ...
- 121
3
votes
3
answers
3k
views
Do any compilers do this optimization for virtual calls?
This just came to mind, and not really sure how to search for this.
Let's say you have the following classes
class A
{
public:
virtual void Foo() = 0;
virtual void ManyFoo(int N)
{
...
- 769
2
votes
4
answers
1k
views
Should a base class implement a virtual method for the most common type or derived class?
Is it okay to implement a virtual method in a base class because I know that the majority of derived classes will use that particular implementation?
Suppose I have the following class hierarchy (in ...
- 39
5
votes
4
answers
14k
views
Is overriding a pure virtual function with default arguments good or bad?
Is overriding a pure virtual function with default arguments good or bad?
class Base {
public:
virtual int func(int i, int j = 10) = 0;
};
class Derived : public Base {
public:
int func(int ...
- 287
-9
votes
1
answer
942
views
Why runtime ploymorphism is required? [closed]
Why runtime ploymorphism is required ? give a real example that "why it came into existence when we have compile time polymorphism??" As mainting the runtime polymorphism requires lot of overhead of ...
- 13
3
votes
1
answer
117
views
How is correct function method called at run-time?
Suppose we have a base class Aand derived class B.
A implements a virtual method foo() which is overloaded in B.
If we have an object test of type B, then the object would surely contain both ...
- 237
2
votes
1
answer
3k
views
What are the consequences of no virtual destructor for this base class?
I found this same code here:
https://stackoverflow.com/a/5854862/257299
struct Base { virtual Base& operator+=(int) = 0; };
struct X : Base
{
X(int n) : n_(n) { }
X& operator+=(int n)...
- 253
2
votes
4
answers
1k
views
Why do I need to declare virtual functions as such?
Example:
We have a base class Base and three subclasses which all implement their own version of doSomething().
In an intermediate function f(Base b), we want to call the relevant version of ...
- 237
3
votes
3
answers
4k
views
When to mark a function as virtual?
I'm trying to understand the idiomatic way to code. I'm using gmock to unit test the components I write. Gmock requires methods to be virtual to be able to mock but the class I'm trying to mock has a ...
- 139
0
votes
1
answer
122
views
Is it possible to detect misuse of passing self type argument in compile time?
I just hit the very basic problem in OOP and I cannot see any working solution except postponing appropriate check until run time.
It is pretty clear notion of an action "do something with value of ...
- 1,496
5
votes
1
answer
18k
views
How does the base class non-virtual function get called when derived class object is assigned to base class?
#include <iostream>
class Base {
private:
int b_value;
public:
void my_func() {std::cout << "This is Base's non-virutal my_func()" << std::endl; }
virtual void ...
- 369
1
vote
1
answer
120
views
Pass data into a constructor or instead create virtual methods?
In an object oriented module describing a database, should I pass DB description data structures to the constructor in the constructors of derived classes, or should I instead create ("virtual" that ...
- 752
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1
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75
views
Virtual method returning a unique collection - how to ensure and hint?
I have a virtual method that returns a collection of items that must be unique. I want to make sure that it will be obvious when overriding the method. What is the best way to do this?
Here is an ...
- 4,827
64
votes
8
answers
65k
views
When NOT to use virtual destructors?
I believed I searched many times about virtual destructors, most mention the purpose of virtual destructors, and why you need virtual destructors. Also I think in most cases destructors need to be ...
- 5,725
33
votes
1
answer
7k
views
Why does C++ not have a "pure" keyword for virtual functions?
I have always wondered why we code
virtual void MyFunction() = 0;
and not
pure virtual void MyFunction();
Is there a reference for the basis of this decision?
