Re: Problem with initialization of array of class objects

From:
"Victor Bazarov" <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Thu, 21 Feb 2008 09:54:18 -0500
Message-ID:
<fpk3ar$5td$1@news.datemas.de>
yatko wrote:

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
{
public:
Foo(int, int);
~Foo();

private:
const int ID;
double int var;


There is no such type as "double int".

};

First method:

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

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


Why is that? Does the compiler complain? (beyond 'double int', I mean)

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
vector.


No, it does not solve the "problem of const members". Putting your
objects in a vector requires the presence of the copy constructor
as well. Not to mention that you need to use 'push_back' instead of
assigning since elements objects[i] do not exist unless you give the
vector some substance (and declaring it does not give substance, not
even empty space). Not to mention a memory leak (actually three
memory leaks).

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

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


Correct. Brace-enclosed initialisers don't work for classes with
parameterized constructors like yours.

You might want to consider generating IDs from a static function;
that way you don't have to provide any and the constructor that takes
one argument could get/generate the ID automatically.

Also, please get into the habit of stating the *requirements*, not
showing non-working solutions, if you want help in class design.

V
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