Perl: Constructing an array of objects

Question

Partially related to this question but different, as this is about constructor calls...

I would like to create an array of a fixed number of objects.

I could do this:

my @objects;
push( @objects, new MyPackage::MyObject() );
push( @objects, new MyPackage::MyObject() );
push( @objects, new MyPackage::MyObject() );
# ...

That's several kinds of ugly. Making it a loop is only marginally better.

Isn't there a way to create an array of (constructor-initialized) objects in Perl?

Afterthought question:

These "objects" I want to create are actually SWIG-generated wrappers for C structs, i.e. data structures without "behaviour" (other than the SWIG-generated get and set functions). I just want to pass the array as a parameter to the C function, which will fill the structures for me; do I need to call constructors at all, or is there a shortcut to having the get functions for reading the struct contents afterwards? (Yes, I am awfully new to OOPerl...)

mob · Accepted Answer · 2011-09-26 15:30:39Z

9

There Is More Than One Concise Way To Do It:

my @objects = map { new MyPackage::MyObject() } 1..$N;

my @objects = ();
push @objects, new MyPackage::MyObject() for 1..$N;

answered Sep 26, 2011 at 15:30

mob

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4 Comments

Bill Ruppert Over a year ago

I just love that first answer, would never have thought of that.

Joel Berger Over a year ago

I voted up the answer, because I would use map too, but boo on the indirect object syntax MyPackage::MyObject0->new() is much much much better, the other way brings many ambiguities.

Joel Berger Over a year ago

In fact, they are talking about removing indirect object syntax in a future version readwriteweb.com/hack/2011/09/… frame 271. Also see perldoc perlobj

DevSolar Over a year ago

The first solution is pure beauty, and exactly what I hoped to find. @Joel Berger: Thanks for the hint, I'd never have thought that the so familiar-looking new ... syntax had footholes in Perl.

Blagovest Buyukliev · Accepted Answer · 2011-09-26 15:29:47Z

2

You can avoid the loop and repeating the same statement by supplying multiple arguments to push:

push(@objects, 
  new MyPackage::MyObject(), 
  new MyPackage::MyObject(), 
  new MyPackage::MyObject());

This is possible because the prototype of push is push ARRAY,LIST.

Or you can do it in a more straightforward way with an array composer (preferable):

my @objects = (
  new MyPackage::MyObject(), 
  new MyPackage::MyObject(), 
  new MyPackage::MyObject(),
);

edited Sep 26, 2011 at 15:29

answered Sep 26, 2011 at 15:24

Blagovest Buyukliev

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Comments

Jonathan M · Accepted Answer · 2011-09-26 15:28:01Z

1

You can say

@objects = (new MyPackage::MyObject(), new MyPackage::MyObject(), new MyPackage::MyObject());

answered Sep 26, 2011 at 15:28

Jonathan M

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Comments

Bill Ruppert · Accepted Answer · 2011-09-26 19:39:58Z

0

You can construct a list of objects and assign it to your array:

my @objects= (
  new MyPackage::MyObject(),
  new MyPackage::MyObject(),
  new MyPackage::MyObject(), 
  # ...
);

answered Sep 26, 2011 at 19:39

Bill Ruppert

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