Declare and initialise an array of struct/class at the same time

Question

1.

I know that it is possible to initialise an array of structures in the declaration. For example:

struct BusStruct
{
    string registration_number;
    string route;
};

struct BusStruct BusDepot[] =
{
    { "ED3280",    "70" },
    { "ED3536",    "73" },
    { "FP6583",    "74A" },
};

If the structure is changed into a class, like this:

class BusClass
{
protected:
    string m_registration_number;
    string m_route;
public:
    // maybe some public functions to help initialisation
};

Is it possible to do the same as for the structure (i.e. declare and initialise an array of classes at the same time)?

2. Am I correct to think that it is not possible to declare and initialise vector<BusStruct> or vector<BusClass> at the same time?

Answer 1

1. No, you would not be able to initialize classes the way you can with structures. But you can write the class constructor inside the array declaration.
2. C++ has no built in way of initializing vectors, unless you want to load the vector from an array that you have initialized.

Answer 2

Is it possible to do the same as for the structure (i.e. declare and initialise an array of classes at the same time)?

Not unless you create a suitable constructor:

class BusClass
{
protected:
    string m_registration_number;
    string m_route;
public:
    // maybe some public functions to help initialisation
    // Indeed:
    BusClass(string const& registration_number, 
             string const& route)
    :m_registration_number(registration_number),
     m_route(route) { }
};

Or you make all members public and omit the constructor, in which case you can use the same initialization syntax as for the struct. But i think that's not what you intended.

Am I correct to think that it is not possible to declare and initialise vector<BusStruct> or vector<BusClass> at the same time?

No it's not possible with current C++. You can however use libraries that make this possible. I recommend Boost.Assign for that. For that, however, your class has to have a constructor, and likewise your struct too - Or you need to create some kind of factory function

BusStruct make_bus(string const& registration_number, 
                   string const& route) { ... }

If you want to keep the struct initializable with the brace enclosed initializer list in other cases.

Answer 3

C++ natively supports two forms of vector initialization and neither is what you are looking for.

1: Every element the same as in:

vector<int> ints(4,1000); //creates a vector of 4 ints, each value is 1000.

2: Copy from an existing vector as in:

vector<int> original(3,1000); //original vector has 3 values, all equal 1000.
vector<int> otherVector(original.begin(),original.end()); //otherVector has 3 values, copied from original vector