Arrays of Structures

The inflatable structure contains an array (the name array). It’s also possible to create arrays whose elements are structures. The technique is exactly the same as for creating arrays of the fundamental types. For example, to create an array of 100 inflatable structures, you could do the following:

inflatable gifts[100];  // array of 100 inflatable structures

This makes gifts an array of inflatables. Hence each element of the array, such as gifts[0] or gifts[99], is an inflatable object and can be used with the membership operator:

cin >> gifts[0].volume;          // use volume member of first struct
cout << gifts[99].price << endl; // display price member of last struct

Keep in mind that gifts itself is an array, not a structure, so constructions such as gifts.price are not valid.

To initialize an array of structures, you combine the rule for initializing arrays (a brace-enclosed, comma-separated list of values for each element) with the rule for structures (a brace-enclosed, comma-separated list of values for each member). Because each element of the array is a structure, its value is represented by a structure initialization. Thus, you wind up with a brace-enclosed, comma-separated list of values, each of which itself is a brace-enclosed, comma-separated list of values:

inflatable guests[2] =              // initializing an array of structs
    {
        {"Bambi", 0.5, 21.99},      // first structure in array
        {"Godzilla", 2000, 565.99}  // next structure in array
    };

As usual, you can format this the way you like. For example, both initializations can be on the same line, or each separate structure member initialization can get a line of its own.

Listing 4.13 shows a short example that uses an array of structures. Note that because guests is an array of inflatable, guest[0] is type inflatable, so you can use it with the dot operator to access a member of the inflatable structure.

Listing 4.13. arrstruc.cpp

// arrstruc.cpp -- an array of structures
#include <iostream>
struct inflatable
{
    char name[20];
    float volume;
    double price;
};
int main()
{
    using namespace std;
    inflatable guests[2] =          // initializing an array of structs
    {
        {"Bambi", 0.5, 21.99},      // first structure in array
        {"Godzilla", 2000, 565.99}  // next structure in array
    };

    cout << "The guests " << guests[0].name << " and " << guests[1].name
         << " have a combined volume of "
         << guests[0].volume + guests[1].volume << " cubic feet. ";
    return 0;
}

Here is the output of the program in Listing 4.13:

The guests Bambi and Godzilla
have a combined volume of 2000.5 cubic feet.