我有以下代码:
接口(interface)&功能定义:
package helper
import "gopkg.in/mgo.v2/bson"
// Defines an interface for identifiable objects
type Identifiable interface {
GetIdentifier() bson.ObjectId
}
// Checks if a slice contains a given object with a given bson.ObjectId
func IsInSlice(id bson.ObjectId, objects []Identifiable) bool {
for _, single := range objects {
if single.GetIdentifier() == id {
return true
}
}
return false
}
满足'Identifiable'的用户结构定义:
package models
import (
"github.com/my/project/services"
"gopkg.in/mgo.v2/bson"
)
type User struct {
Id bson.ObjectId `json:"_id,omitempty" bson:"_id,omitempty"`
Username string `json:"username" bson:"username"`
Email string `json:"email" bson:"email"`
Password string `json:"password" bson:"password"`
Albums []bson.ObjectId `json:"albums,omitempty" bson:"albums,omitempty"`
Friends []bson.ObjectId `json:"friends,omitempty" bson:"friends,omitempty"`
}
func GetUserById(id string) (err error, user *User) {
dbConnection, dbCollection := services.GetDbConnection("users")
defer dbConnection.Close()
err = dbCollection.Find(bson.M{"_id": bson.ObjectIdHex(id)}).One(&user)
return err, user
}
func (u *User) GetIdentifier() bson.ObjectId {
return u.Id
}
检查 slice 内对象是否存在的测试:
package controllers
import (
"github.com/my/project/helper"
"gopkg.in/mgo.v2/bson"
)
var testerId = bson.NewObjectId()
var users = []models.Users{}
/* Some code to get users from db */
if !helper.IsInSlice(testerId, users) {
t.Fatalf("User is not saved in the database")
}
当我尝试编译测试时,出现错误:undefined helper.IsInSlice
。当我重写 IsInSlice
方法以不采用 []Identifiable
而采用 []models.User
时,它工作正常。
有什么想法吗?
最佳答案
您的问题是您试图将 []models.Users{}
类型的值用作 []Identifiable
类型的值。虽然 models.Users
实现了 Identifiable
,但 Go 的类型系统的设计使得实现接口(interface)的值 slice 不能用作(或转换为)接口(interface)类型的 slice 。
请参阅 Go 规范的 section on conversions了解更多详情。
关于interface - 去编译错误 "undefined function",我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/27755954/