Variable in handler is not passing to template

Question

Learning Go and Gin from here. So I have a router like this

userRoutes.POST("/login", ensureNotLoggedIn(), performLogin)

and the handler function is like this

func performLogin(c *gin.Context) {
  username := c.PostForm("username")
  password := c.PostForm("password")
  if isUserValid(username, password) {
    token := generateSessionToken()
    c.SetCookie("token", token, 3600, "", "", false, true)
    //is_logged_in is not working in template
    c.Set("is_logged_in", true)
    render(c, gin.H{"title": "Successful Login"}, "login-successful.html")
  } else {
    c.HTML(http.StatusBadRequest, "login.html", gin.H{
        "ErrorTitle":   "Login Failed",
        "ErrorMessage": "Invalid credentials provided",
    })
  }
}

and my template is like

{{ if .is_logged_in }}
      <li><a href="/article/create">Create Article</a></li>
{{ end }}
{{ if not .is_logged_in }}
    <li><a href="/u/register">Register</a></li>
{{end}}

But in the end this variable in template seems not working, only the second section shows, the first link 'Create Article' is always hiding.

Update

I changed the handler function to something like this,

        render(c, gin.H{"title": "Successful Login", "is_logged_in": c.MustGet("is_logged_in").(bool)}, "login-successful.html")

explicitly passing the variable. Now the template element hide and show is correct. So was there anything changed in Golang or Gin to make .Set() behaving differently?

Just for the record, I've just learned that 'this is the way it's supposed to be'. See https://github.com/gin-gonic/gin/issues/1512#issuecomment-418021853 — citing @[isgj](https://github.com/isgj) on GitHub, _No, the template can see only what you pass to the `c.HTML(...)`. What you set with `c.Set(...)` can be seen only by the middleware and the handler._ — Gwyneth Llewelyn, Jun 27 '20 at 19:28
Also, since this example comes from [this most wonderful tutorial](https://chenyitian.gitbooks.io/gin-tutorials/tdd/11.html) by Chen Yi-Tian, maybe, if someone has a way to contact him, it would be nice if he could update that specific page explaining how variables are passed to templates... — Gwyneth Llewelyn, Jun 27 '20 at 19:54

score 2 · Answer 1 · edited Aug 10 '20 at 03:50

Do you load the template firstly?

func main() {
router := gin.Default()
router.LoadHTMLGlob("templates/*")
//router.LoadHTMLFiles("templates/template1.html", "templates/template2.html")
router.GET("/index", func(c *gin.Context) {
    c.HTML(http.StatusOK, "index.tmpl", gin.H{
        "title": "Main website",
    })
})
router.Run(":8080")
}

templates/index.tmpl

<html>
<h1>
    {{ .title }}
</h1>

Variable in handler is not passing to template

1 Answers1