十七、iterator 迭代器模式

https://refactoringguru.cn/design-patterns/iterator

为了集合数据的安全性, 或方便迭代, 可以用迭代器接口. 屏蔽复杂的内部逻辑, 外部只能使用迭代器遍历

17.1 user_slice

├── collection.go
├── collection_test.go
├── iterator.go
├── readme.md
└── user.go

17.1.1 collection_test.go

package _71user_sliceimport ("fmt""testing"
)/*
=== RUN   TestCollection
1 Tom
2 Jack
--- PASS: TestCollection (0.00s)
PASS
*/
func TestCollection(t *testing.T) {c := UserCollection{users: []*User{&User{"1", "Tom"}, {"2", "Jack"}}}iter := c.createIterator()for iter.hasNext() {v := iter.getNext()fmt.Println(v.ID, v.Name)}
}

17.1.2 collection.go

package _71user_slicetype Collection interface {createIterator() Iterator
}type UserCollection struct {users []*User
}func (uc *UserCollection) createIterator() Iterator {return &userIterator{users: uc.users,}
}

17.1.3 iterator.go

package _71user_slicetype Iterator interface {hasNext() boolgetNext() *User
}type userIterator struct {index intusers []*User
}func (ui *userIterator) hasNext() bool {return ui.index < len(ui.users)
}func (ui *userIterator) getNext() *User {if ui.hasNext() {v := ui.users[ui.index]ui.index++return v}return nil
}

17.1.4 user.go

package _71user_slicetype User struct {ID   stringName string
}