Basic declaration

A basic struct is declared as follows:

// User describes a user
type User struct {
	FirstName, LastName string
	Email               string
	Age                 int
	userID              int
}

// FullName returns full name of a user
func (u *User) FullName() string {
	return fmt.Sprintf("%s %s", u.FirstName, u.LastName)
}

func main() {
	// zero value of struct
	var u User
	fmt.Printf("u: %#v\n\n", u)

	// pu is *User i.e. a pointer to User struct
	pu := new(User)
	pu.Age = 33
	fmt.Printf("*pu: %#v\n", *pu)

	// &User{} is the same as new(User)
	pu = &User{}
	pu.Age = 18
	fmt.Printf("*pu: %#v\n", *pu)

	pu.FirstName, pu.LastName = "Jane", "Doe"
	fmt.Printf("pu.FullName(): %s\n", pu.FullName())
}

try online

u: main.User{FirstName:"", LastName:"", Email:"", Age:0, userID:0}

*pu: main.User{FirstName:"", LastName:"", Email:"", Age:33, userID:0}
*pu: main.User{FirstName:"", LastName:"", Email:"", Age:18, userID:0}
pu.FullName(): Jane Doe

Each value is called a field.

Fields are usually written one per line, with the field’s name preceeding its type.

Consecutive fields of the same type may be combined, as FirstName and LastName in the above example.

Field names that start with upper case (FirstName, Email) are public i.e. accesible by all code.

Field names that start with lower case (userID) are private and only accessible by code in the same package.

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