gorilla 网络工具包 : len(session. Flashes()) 为 0

Question

我有一个注册表单，我想用简单的逻辑放在一起，我在服务器端用简单的 ifs 检查表单验证，例如

if username == "" || < 5 {
    session.AddFlash("Username is too short")
    session.Save(r, w)
}

那在我做的验证结束时工作正常(出于调试目的)

fmt.Println(len(session.Flashes())) which returns 3

然后我检查是否有像这样的表单错误

if len(session.Flashes()) != 0 {
    // Perform Redirect and show flashes
} else {
    // Set proper session variables and log user in
}

那么 if 3 > 0 为什么触发 else 语句而不是 if 语句的第一部分？我只是不确定为什么会这样。谢谢，如果您需要更多信息，请告诉我，实际代码片段:

if username == "" || len(username) < 4 {
    session.AddFlash("Username is too short")
    session.Save(r, w)
}
if email == "" || len(email) < 5 {
    session.AddFlash("Email is too short")
    session.Save(r, w)
}
if firstname == "" || len(firstname) < 3 {
    session.AddFlash("Firstname is too short")
    session.Save(r, w)
}
if lastname == "" || len(lastname) < 3 {
    session.AddFlash("Lastname is too short")
    session.Save(r, w)
}

fmt.Println(len(session.Flashes()) > 0) // true

if len(session.Flashes()) != 0 {
    fmt.Println("Why am I here also")
    type Page struct {
        Title    string
        Username interface{}
        Errors   []interface{}
    }

    session, _ := common.GetSession(r)
    data := &Page{"Register", session.Values["username"], session.Flashes()}
    session.Save(r, w)

    tmpl, err := template.ParseFiles("views/register/register.html")
    if err != nil {
        http.Error(w, "Failed to load page.", 500)
    }
    tmpl.ExecuteTemplate(w, "register", data)
} else {
    fmt.Println("Why am I here")
    _, err := db.Query("// Perform DB Query")
    if err != nil {
        http.Error(w, "Sorry we had trouble saving your account to the database, try again in a bit.", 500)
    }

    session.Values["username"] = r.FormValue("username")
    session.Values["authenticated"] = true

    session.Save(r, w)

    http.Redirect(w, r, "/", 303)
}

Answer 1

它没有很好的记录，但显然 Flashes 从 session 中删除 flashes 并返回它们:

func (s *Session) Flashes(vars ...string) []interface{} {
    var flashes []interface{}
    key := flashesKey
    if len(vars) > 0 {
        key = vars[0]
    }
    if v, ok := s.Values[key]; ok {
        // Drop the flashes and return it.
        delete(s.Values, key)
        flashes = v.([]interface{})
    }
    return flashes
}

源代码here .

这里的解决方案是使用一个单独的变量来保存验证状态:

valid := true
if username == "" || len(username) < 4 {
    valid = false
    session.AddFlash("Username is too short")
    session.Save(r, w)
}
// ...
if !valid {
    // ...
} else {
    // ...
}

编辑另一种获取闪光而不删除它们的方法是直接从 Values 获取它们:

flashes := session.Values["_flash"].([]interface{})