Re: Problem with initialization of array of class objects

James Kanze <>
Fri, 22 Feb 2008 05:26:45 -0800 (PST)
On Feb 21, 3:49 pm, "Alf P. Steinbach" <> wrote:

* yatko:

I want to define an array of objects and initialize them,
but I don't know how I could do that simply. I have searched
over net, and have found a few solutions. Does anybody has a
better, simple solution?

Suppose there is a Foo class that has const member.

class Foo
Foo(int, int);

const int ID;

double int var;


First method:

Foo objects [MAX] = {Foo(0,1),Foo(1,2),Foo(2,3)};

This method works nicely.

For his class above, yes. As he later indicates, he was holding
out on us---his actual class contains a boost::mutex, which
isn't copiable.

// This one requires copy constructor, but I have const members, so it
doesn't work for me.

It's opposite: the method below requires copy constructor,
while the one above doesn't.

No. They both require the copy constructor. To begin with,
aggregate initialization is copy initialization. And even if it
weren't, his initialization expression in both cases has the
type Foo, so the copy constructor will be called.

Of course, the presence of a const member doesn't cause any
problems for the copy constructor. His class above has a
perfectly good, compiler generated copy constructor.

Second method:

std::vector<Foo> objects;

objects[0] = * (new Foo(0,1));
objects[1] = * (new Foo(1,2));
objects[2] = * (new Foo(2,3));

//This one solves problem of const members, but I dont want to use

This doesn't work for const members.

Right, because is uses assignment, and not copy construction.

I want to initialize the array as following, but it doesn't work.

Foo objects[MAX] = {{0,1},{1,2},{2,3}};

Works OK.

Huh? Foo is not an aggregate, and so cannot be initialized
using aggregate initialization. To initialize the array, you
must provide a list of Foo, or of things which can be implicitly
converted to Foo---since Foo doesn't have a converting
constructor, there isn't anything which can be converted to Foo.

James Kanze (GABI Software)
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