C++ Create class that inherits a Vector

Question

I would like to know if I can create a class that inherits a vector that contains vectors (2d) and can write my own methods.

using matrix = vector<vector<float>>;

class MyClass: public matrix;

...

MyClass m;

m = {{1,2,3}, {4,5,6}, {7,8,9}}

m.randomize(); // my method
m.pop_back() //class vector method

The std:: collections are not designed to be inherited from. — Richard Critten
– Richard Critten, Commented Jul 11, 2021 at 20:29
Does this answer your question? Thou shalt not inherit from std::vector — Richard Critten
– Richard Critten, Commented Jul 11, 2021 at 20:32
@RichardCritten "The std:: collections are not designed to be inherited from" That's not exactly true. They don't have virtual destructors which means they can't be deleted polymorphically from a base pointer; but there is nothing that prohibits them being inherited from. Even the answers on the linked question indicate the same. I'm not suggesting inheriting is good advice in this case; just that stating they are "not designed to be inherited from" is factually incorrect. — Bitwize
– Bitwize, Commented Jul 11, 2021 at 20:38

Ted Lyngmo · Accepted Answer · 2021-07-11 20:33:02Z

4

I would like to know if I can create a class that inherits a vector that contains vectors (2d) and can write my own methods

Yes, nothing prohibits this although it's generally recommended to use composition instead. One reason why it's not recommended is that the standard containers destructor is not virtual so deleting objects though base class pointers doesn't work.

answered Jul 11, 2021 at 20:33

Ted Lyngmo

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Sneftel · Accepted Answer · 2021-07-11 20:34:20Z

3

Sure, but that’s not what you want. Why should MyClass have a push_back method which can be used to make the matrix non-square? Why should its resize method set the number of rows but not the number of columns? Inheriting from a non-abstract class is almost never a good idea, compared to either composition or refactoring.

answered Jul 11, 2021 at 20:34

Sneftel

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