how to pass vectors

[density]

lets say i have a function that calls a function that fills a vector (declared in the header file) like this:

void
class::foo()
{
bar( pointer)
}
void
class::bar( pointer )
{
int vec(array, array + sizeof array / sizeof array[0]) ; 
}

and i want to use that vector in many other functions in the class like this:

string 
class::foobar_str() const
{
need to read vector here and return const string
}

i tried a few things but nothing worked. Any help will be greatly appreciated. Thanks.

[ne555]

> i tried a few things but nothing worked
maybe you should try to write in c++

I don't understand your description, and your code makes no sense.

class foo{
   std::vector<int> v;
public:
   void fill(){
      int n;
      while(std::cin>>n)
         v.push_back(n);
   }
   std::string bar() const{
      return v.empty()? "hello": "world";
   }
};

[density]

obviously its not real code. its meant to describe what i am trying to do. let me ask this? if i a fill a vector in one function, and that vector is declared in the header file, will that filled vector be able to be read by other member functions? i don't want to have to return it, or pass it in parameter. i want to set it once, the computation is to expensive to keep doing and returning.

[ne555]

¿how is the vector declared?
If it is a member variable, all member functions may access it
If it is a static member variable, all member functions from all the objects of that class may access it
If it is global, all can access it.

[MikeyBoy]

A vector is just an object like any other. Its persistence will depend on how you declare it, just as ne555 says, just like any other object.

[density]

hey thanks. the vector is declared in the private section of the header file.

class child : public parent
{
public:
   //functions declared here
protected:
  //functions declared here
private:
  //functions declared here

  //vector declared here
}

so once the vector is filled, all the other functions can read the contents of that vector?

[MikeyBoy]

The vector will keep its state for the lifetime of the object of which it is a member. Just like any other data member.

[density]

Thanks. And because it is declared in the header, it is available to every other function without being passed as parameter or returned???

[MikeyBoy]

It's declared as a private member - as is usually correct for class data members - so it is visible only to other methods of the class.

If any code outside the class needs to access the contents of the vector, you'll need to pass it via a public method. When doing so, you'll need to consider whether you're passing a copy of the vector, or a reference/pointer to the actual data member, considering issues such as separation of interface and implementation, ownership of data, and the lifetime of the class and the validity of those pointers/references.

[density]

Thanks!

[MikeyBoy]

You're welcome :)