This article was done using my notes from:
Alexander Shvets (2019), Dive into Design Patterns, Refactoring.Guru
Iterator
Iterator allows sequential traversal through a complex data structure without exposing its internal details.
Structure
Code
package main
import "fmt"
type Collection interface {
createIterator() Iterator
}
type UserCollection struct {
users []*User
}
func (u *UserCollection) createIterator() Iterator {
return &UserIterator{
users: u.users,
}
}
type Iterator interface {
hasNext() bool
getNext() *User
}
type UserIterator struct {
index int
users []*User
}
func (u *UserIterator) hasNext() bool {
if u.index < len(u.users) {
return true
}
return false
}
func (u *UserIterator) getNext() *User {
if u.hasNext() {
user := u.users[u.index]
u.index++
return user
}
return nil
}
type User struct {
name string
age int
}
func main() {
user1 := &User{
name: "a",
age: 30,
}
user2 := &User{
name: "b",
age: 20,
}
userCollection := &UserCollection{
users: []*User{user1, user2},
}
iterator := userCollection.createIterator()
for iterator.hasNext() {
user := iterator.getNext()
fmt.Printf("User is %+v\n", user)
}
}