Arrays initialization on constructors

Question

I'm trying to convert a program to OOP. The program works with a few arrays:

int tipoBilletes[9] = { 500,300,200,100,50,20,10,1,2 };
int cantBilletes[9] = {0};

So for my conversion, I declared in the header file this:

int *tipoBilletes;
int *cantBilletes;

and in the constructor I wrote

tipoBilletes = new int[9];
cantBilletes = new int[9];

tipoBilletes[0] = 500;
tipoBilletes[1] = 300;
tipoBilletes[2] = 200;
...

It works fine.

My question is, is there any way to initialize it like in Java?

int[] tipoBilletes = new int[]{ 500,300 };

rather than having to set each element one by one?

Not until the new version of C++ comes out. But you should be using std::vector, not new[]. Also, what benefits are you gaining by changing it from a fixed-size array to a dynamic array? — GManNickG
– GManNickG, Commented Jan 20, 2011 at 23:12
I still can't comprehend how it's not possible to have something as simple as a plain local array of objects without a default constructor in old C++... Have they, like, forgotten about it when making C++03, or what? — Kos
– Kos, Commented Jan 20, 2011 at 23:17
well i used dynamic array , cuz i thought that i could do the initialization java - like — Jose De Gouveia
– Jose De Gouveia, Commented Jan 23, 2011 at 15:04
@BoundaryImposition sorry, I can't really remember what I have meant, it's been a while. — Kos
– Kos, Commented May 3, 2017 at 12:27

James McNellis · Accepted Answer · 2011-01-20 23:12:24Z

4

No, but you don't necessarily nead to write out each assignment independently. Another option would be:

const int TIPO_BILLETES_COUNT = 9;
const int initialData[TIPO_BILLETES_COUNT] = { 500,200,300,100,50,20,10,1,2 };
std::copy(initialData, initialData + TIPO_BILLETES_COUNT, tipoBilletes);

(Note that you should almost certainly be using a std::vector for this instead of manual dynamic allocation. The initialization is no different with a std::vector though once you've resized it.)

answered Jan 20, 2011 at 23:12

James McNellis

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2 Comments

Fred Larson Over a year ago

Actually, for the std::vector option, you could initialize the vector using its constructor that takes a pair of iterators instead of std::copy.

James McNellis Over a year ago

@Fred: Yep, you could do that too!

J. Calleja · Accepted Answer · 2011-01-20 23:43:46Z

2

If you use std::vector you can use boost::assign:

#include <vector>
#include <boost/assign/std/vector.hpp>  
//... 
using namespace boost::assign;
std::vector<int> tipoBilletes;
tipoBilletes += 500, 300, 200, 100, 50, 20, 10, 1, 2;

On the other hand, you should consider using the fixed-size array if it is small and constant size.

answered Jan 20, 2011 at 23:43

J. Calleja

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Comments

Richard · Accepted Answer · 2022-05-28 13:56:31Z

1

My question is, is there any way to initialize it like in Java?

Yes, starting from C++11 there is a way to do this as shown below. Note that this was proposed in p1009r2.

int *tipoBilletes = new int[] { 500,300,200,100,50,20,10,1,2 };

From new expression documentation the above creates an array of type int[9].

Working demo

Note that you could just use std::vector that will do the memory management for you so that you don't have to worry about memory leaks. But the question was not about how to use std::vector.

edited May 28, 2022 at 13:56

answered May 19, 2022 at 7:10

Richard

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