Re: questions about pointers in container

"Daniel T." <>
Wed, 06 Aug 2008 20:09:21 -0400
<> wrote:

"Daniel T." <> wrote: wrote:

"Daniel T." <> wrote: wrote:

as this example,


If my purpose is initialize data from xml files and store them in the
vector, so they can be used in class B by other member functions, do
you think functionP is a viable function(will a could go away after
out of the function)?
If not, is there a better solution than using functionPt?

I read that it is not a good design to have container for pointers(C++
FAQs), but I cannot see how I can get around it in my situation.

Newbie questions, thanks for the help


class A{
? ?....

class B{

void functionPt(){
? A* aPt ;

aPt has not been initialized. Copying it into a vector is technically
undefined behavior.

? vPt.push_back(aPt);


void functionP(){
? ...
? A a;
? ?v.push_back(a);

? ?vector<A*> vPt;
? ?vector<A> ?v;


Thanks. My fault. My intention is A* aPt = new A;

Now you have a leak.

not really. my ~B will iterate the vector and call delete.

That's not in the code you posted though... You have to add it to the
code, also what about the copy constructor and the assignment operator?

Once you take all of the above into account, and then compare the volume
of code you have to write in order to correctly implement the vector<A*>
solution, to how little you have to write to implement the vector<A>
solution, It is easy to see which is better.

Let's look at the two with all these issues covered:

class A { };

class B1 {
   vector< A > vec;
   void func() {
      vec.push_back( A() );


   // I may have missed some bits, but I think this is generally correct.
class B2 {
   vector< A* > vec;
   B2( const B2& o ) : vec( o.vec.size() ) {
      try {
         vector< A* >::iterator o_it = o.vec.begin();
         for ( vector< A* >::iterator it = vec.begin();
               it != vec.end();
               ++it ) {
            *it = new A( *o_it );
      catch ( ... ) {
         for ( vector< A* >::iterator it = vec.begin();
               it != vec.end();
               ++it )
            delete *it;

   ~B2() {
      for ( vector< A* >::iterator it = vec.begin();
            it != vec.end();
            ++it )
         delete *it;

   void operator=( const B2& o ) {
      B2 tmp( o );
      swap( tmp.vec, vec );

   void func() {
      vec.push_back( new A );

Why would you implement B2 if you didn't absolutely have to?

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