go语言设计模式之proxy

package proxy

import (
	//"errors"
	"fmt"
)

type UserFinder interface {
	FindUser(id int32) (User, error)
}

type User struct {
	ID int32
}

type UserList []User

func (t *UserList) FindUser(id int32) (User, error) {
	for i := 0; i < len(*t); i++ {
		if (*t)[i].ID == id {
			return (*t)[i], nil
		}
	}
	return User{}, fmt.Errorf("User %d could not be found\n", id)
}

type UserListProxy struct {
	SomeDatabase           UserList
	StackCache             UserList
	StackCapacity          int
	DidLastSearchUsedCache bool
}

func (u *UserListProxy) FindUser(id int32) (User, error) {
	user, err := u.StackCache.FindUser(id)
	if err == nil {
		fmt.Println("Returning user from cache")
		u.DidLastSearchUsedCache = true

		return user, nil
	} else {
		user, err = u.SomeDatabase.FindUser(id)
		if err != nil {
			return User{}, err
		}
		fmt.Println("Returning  from database")
		u.addUserToStack(user)
		u.DidLastSearchUsedCache = false
		return user, nil
	}
}

func (t *UserList) addUser(newUser User) {
	*t = append(*t, newUser)
}

func (u *UserListProxy) addUserToStack(user User) {
	if len(u.StackCache) >= u.StackCapacity {
		u.StackCache = append(u.StackCache[1:], user)
	} else {
		u.StackCache.addUser(user)
	}
}
packag