Re: array of objects of parametrized constructor

From:

"Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Wed, 04 May 2011 11:11:43 +0200

Message-ID:

<ipr4j8$r2v$1@dont-email.me>

* Ian Collins, on 04.05.2011 00:18:

On 05/ 4/11 07:29 AM, Alf P. Steinbach /Usenet wrote:

* asit, on 03.05.2011 20:32:

consider this class

class A
{
    int a;
public:
    A(int x):a(x)
    {
        cout<<"Parametrized constructor"<<endl;
    }
};

How can I create array of objects ??

I can't add the default constructor and overload the parametrized
constructor.

The simplest solution is to use std::vector, from the<vector> header.

E.g.

      std::vector<A> myArray;

      myArray.push_back( A( 1 ) );
      //...

And that's what you should be doing anyway, as a beginner. Don't mess around
with raw arrays. For that matter, don't add assembly language stubs either. ;-)

In this case, using a temporary array as a helper would be fine:

A tmp[] = { 1,2,3,4 };
std::vector<A> a(tmp, tmp+(sizeof(tmp)/sizeof(A)) );

I disagree.

Even an experienced programmer like yourself gets it, well not technically wrong
but pretty imperfect. :-(

If done, it would better look like this:

int const tmp[] = { 1,2,3,4 };
std::vector<A> a(tmp, tmp+(sizeof(tmp)/sizeof(*tmp)) );

But since it's so easy to get wrong, and since it creates an association where
use of raw arrays seems to be OK in general, I recommend not doing it.

Cheers,

- Alf

--
blog at <url: http://alfps.wordpress.com>