How do I declare an array of objects whose class has no default constructor?

Question

If a class has only one constructor with one parameter, how to declare an array? I know that vector is recommended in this case. For example, if I have a class

Answer 1

Another option might be to use an array of boost::optional:

boost::optional foos[10]; // No construction takes place
                               // (similar to vector::reserve)

foos[i] = Foo(3); // Actual construction

One caveat is that you'll have to access the elements with pointer syntax:

bar(*foos[2]); // "bar" is a function taking a "Foo"

std::cout << foos[3]->baz(); // "baz" is a member of "Foo"

You must also be careful not to access an unitialized element.

Another caveat is that this not a true replacement for an array of Foo, as you won't be able to pass it to a function that expects the latter.