英文:
Need type assertion on functions
问题
我正在尝试学习类型断言和类型转换，对我来说有点复杂。
我有这个例子：（我正在使用gin框架）
type Env struct {db *sql.DB}func main() {r := gin.Default()// 初始化会话管理（基于cookie）store := sessions.NewCookieStore([]byte("secret"))r.Use(sessions.Sessions("mysession", store))db, _ := sql.Open("sqlite3", "./libreread.db")defer db.Close()env := &Env{db: db}r.GET("/", env.GetHomePage)}func (e *Env) _GetUserId(email string) int64 {rows, err := e.db.Query("SELECT `id` FROM `user` WHERE `email` = ?", email)CheckError(err)var userId int64if rows.Next() {err := rows.Scan(&userId)CheckError(err)}rows.Close()return userId}func (e *Env) GetHomePage(c *gin.Context) {session := sessions.Default(c)email := session.Get("email")if email != nil {name := c.Param("bookname")userId := e._GetUserId(email) // 我在这里卡住了。}}
所以，在上面的代码中...我正在设置db Env类型并将其传递给路由函数。从那里，我需要调用另一个函数。如何做到这一点？
当我调用e._GetUserId(email)时，它显示：
无法将email（类型为interface {}）转换为Env类型：需要类型断言
如何解决这个问题？我需要在Env类型中使用interface{}而不是struct吗？
英文:
I'm trying to learn type assertion and conversion. It's kinda complicated for me.
I have this example: (I'm using gin framework)
type Env struct {db *sql.DB}func main() {r := gin.Default()// Initiate session management (cookie-based)store := sessions.NewCookieStore([]byte("secret"))r.Use(sessions.Sessions("mysession", store))db, _ := sql.Open("sqlite3", "./libreread.db")defer db.Close()env := &Env{db: db}r.GET("/", env.GetHomePage)}func (e *Env) _GetUserId(email string) int64 {rows, err := e.db.Query("SELECT `id` FROM `user` WHERE `email` = ?", email)CheckError(err)var userId int64if rows.Next() {err := rows.Scan(&userId)CheckError(err)}rows.Close()return userId}func (e *Env) GetHomePage(c *gin.Context) {session := sessions.Default(c)email := session.Get("email")if email != nil {name := c.Param("bookname")userId := e._GetUserId(email) // I'm stuck here.}
So, in the above code.. I'm setting db Env type and passing it to router functions. From there, I need to call another function. How to do that?
When I call e._GetUserId(email), it says
cannot convert email (type interface {}) to type Env: need type assertion
How to solve this problem?. Do I need to use inferface{} instead of struct for Env type?
答案1
得分: 7
根据我评论中的对话起草答案。
方法 session.Get("email") 返回 interface{} 类型。
而方法 e._GetUserId() 接受字符串参数，所以你需要进行类型断言，如下所示 -
e._GetUserId(email.(string))
英文:
Drafting answer based on conversation from my comments.
Method session.Get("email") returns interface{} type.
And method e._GetUserId() accepts string parameter, so you need to do type assertion as string like -
e._GetUserId(email.(string))
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