C++ vectors of classes with constructors

Question

//Using g++ and ubuntu.
#include 
using namespace std;

Define a class:

class foo(){
(...)
foo(int arg1, double arg2);         


        

Answer 1

vector bar(10); //error: no matching function for call to 'foo::foo()'

This is failing because the std::vector constructor you're calling is

explicit vector ( size_type n, const T& value= T(), const Allocator& = Allocator() );

As you can see, it is trying to fill the vector with 10 calls to the default constructor of foo which does not exist.

Also, all your examples featuring new will fail because the vector is expecting an object of type foo, not foo *. Furthermore, changing to vector will fail too unless you manually delete every member before clearing the vector. If you really want to go the dynamic memory allocation route create a vector< shared_ptr< foo > >. shared_ptr is available in the Boost libraries or if your compiler includes TR1 libraries it'll be present in the header within the std::tr1 namespace or if your compiler has C++0x libraries it'll be available in the std namespace itself.

What you should probably do is the following:

vector bar;
bar.reserve(10);
bar.push_back( foo( 1, 2 ) );
...
...
bar.push_back( foo( 10, 20 ) ); //10 times