C++ Array Declaration in Header

Question

I want to create a class but I am not sure if I am declaring an array correctly in a class.

my header file

#ifndef SOMECLASS_H
#define SOMECLASS_H
#include <string>    
class MyClass {
    public:
       MyClass();
       ~MyClass();
    private:
       std:string myStringArray[];
       int myIntegerArray[];
};    
#endif SOMECLASS_H

my class file

#include "someClass.h"

MyClass::MyClass() {
    std::string myStringArray[] = {"Option1","Option2",
                                   "Option3","Option4"};
    int myIntegerArray[] = {1,2,3,4};
}

But that doesn't seem to work... I want to initialize the array when the class is created. Can someone please explain to me what I am doing wrong. Thank you.

Unless you know at compile-time (which you seem to do) you might want a std::vector. Otherwise read about std::array. You also want to read about member initializer lists. — Some programmer dude
– Some programmer dude, Commented Nov 10, 2013 at 18:36

Ken P · Accepted Answer · 2013-11-10 18:42:52Z

2

Unlike Java, C++ requires the size of the array be known (and declared) at compile-time. If you want to use an array-type variable where the size is NOT known at compile-time, you should use a std::vector.

answered Nov 10, 2013 at 18:42

Ken P

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Manu343726 · Accepted Answer · 2013-11-10 18:44:20Z

1

You should specify the size of an array, or initialize it at its declaration letting the compiler to infer its size.

If you don't know the size of the array at the point of its declaration, a raw array is not the good data structure for your problem. Use std::vector if the size is known at runtime. In the future, if the size of the container is known at runtime but will not be changed,std::dynarray (Which was discarded from C++14 :( ) would be a good alternative.

Also consider to use C++11 std::array instead of C arrays, it has a lot of improvements (A interface/syntax fully compatible/shared with other STL algortihms and containers) compared to a naked C array.

edited Nov 10, 2013 at 18:44

answered Nov 10, 2013 at 18:37

Manu343726

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