Declaring readonly variables on a C++ class or struct

Question

I\'m coming to C++ from C# and const-correctness is still new to me. In C# I could declare a property like this:

class Type 
{
    public readonly int x;
            


        

Answer 1

Rather than a collection of constants, you could have a constant collection. The property of being constant seems to pertain to your use case, not the data model itself. Like so:

struct extent { int width; int height; };

const extent e { 20, 30 };

It's possible to have specifically constant data members of a class, but then you need to write a constructor to initialize it:

struct Foo
{
    const int x;
    int & y;
    int z;

    Foo(int a, int & b) : x(a + b), y(b), z(b - a) {  }
};

(The example also shows another type of data member that needs to be initialized: references.)

Of course, structs and classes are the same thing.