resizing string members in constructor

I've to make sure the string members are of fixed size during construction. However they can increase their size after construction is done and later in the program, user chooses to add more text to it.

class A {
    std::string name;
    std::string desc;
    int num;

  public:
    A(int, std::string, std::string);
    .....
}

Now if I do this -

A(int n, std::string name, std::string d) : 
    num(n),
    name(name),
    desc(d) 
{
    ....
}

I'll have to call resize() inside the constructor body. This means there exists full string lengths at some time during the construction. Let's say I want the initial size to be 5, and user passes 20 chars string, during the construction and before resize(), the string would contain 20 chars, right?

Now I was thinking along the lines of doing this -

A(int n, std::string name, std::string d) : 
    num(n)
{
    name = name;
    desc = d;
    name.resize(5);
    desc.resize(5);
    ....
}

But this would be same right?

Should I instead call resize() on passed parameters itself? Or is there any better way..