9.3 Nested Structs and Arrays of Structs

A struct can contain another struct. This is composition, and it lets you split complex data into clearer smaller pieces.

typedef struct {
    int year;
    int month;
    int day;
} Date;

typedef struct {
    char name[32];
    Date birthday;
    int score;
} Student;

Access nested members by continuing to use .:

Student s = {"Ada", {1815, 12, 10}, 96};
printf("%d\n", s.birthday.year);   // 1815

Put many records into an array of structs to process them like a table:

Student class[3] = {
    {"Ada", {1815, 12, 10}, 96},
    {"Bob", {2000, 1, 1}, 88},
    {"Cher", {1999, 5, 9}, 73}
};

for (int i = 0; i < 3; i++) {
    printf("%s %d\n", class[i].name, class[i].score);
}

A struct such as Date can also be reused inside several other structs, which keeps relationships between types clearer.

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