Pass different data to different html templates

So I have several html template files.

templates/
— head.html
— header.html
— home.html
— register.hml

head.html

{{define "head"}}
<!DOCTYPE html>
<html>
 <head>
  //Some meta tags and including some css/js files.
 </head>
 {{end}}

header.html Now here I'm using if/else statement. Based on the data, i'm showing login and register form, or "logged in as ..." message.

{{define "header"}}
<body>
  <header>
  //Some logo + navigation.

    {{if.}}
       //If there is data display: 
       "logged in as" {{.}}
    {{else}}
       //Else display a login/register form
    {{end}}
  </header>
{{end}}

home.html

{{define "home"}}
{{template "head" .}}
{{template "header" .}}
   //some HTML code.
</body>
</html>
{{end}}

register.html Now here I'm using if statement to check if the user have failed to register and show him what the error is.

{{define "register"}}
{{template "head" .}}
{{template "header" .}}
//Displaying register form, so the user can register in the website.
    {{if.}}
      //If there is data, display message. 
     "registrain failed, reason:" {{.}}
    {{end}}
</body>
</html>
{{end}}

The problem is that when I go to the register page and fail to register the error message is displayed, but also the header changes to "logged in as the error message that have to be shown only for the registration form"

This is my Golang code:

package main

import (
	"html/template"
	"net/http"
)

//Caching all templates.
var tpl = template.Must(template.ParseGlob("templates/*.html"))

func main() {
	//Serving static files from the assets folder like CSS and JS files.
	http.Handle("/assets/", http.StripPrefix("/assets/", http.FileServer(http.Dir("assets"))))

	//Routing and handlers
	http.HandleFunc("/", indexHandler)
	http.HandleFunc("/logout", logoutHandler)
	http.HandleFunc("/register", registerHandler)
	
	http.ListenAndServe(":8000", nil)
}
//My handler for the root
func indexHandler(w http.ResponseWriter, r *http.Request) {
    //If there is cookie I pass the value of the cookie to the template,
    //so in the website to display "logged in as: cookie value"
	cookie, err := r.Cookie("username")
	if err != nil {
		tpl.ExecuteTemplate(w, "home", nil)
	} else {
		tpl.ExecuteTemplate(w, "home", cookie.Value)
	}

}

//My handler for /register
func registerHandler(w http.ResponseWriter, r *http.Request) {

	switch r.Method {
	case "GET":
		tpl.ExecuteTemplate(w, "register", nil)

	case "POST":
		//validateUser() returns error if validation of the string fails.
		_, err := validateUser(r.FormValue("username"))
		if err != nil {
			tpl.ExecuteTemplate(w, "register", err)
			fmt.Sprintln(err)
		} else {
			//Some succes message. and redirecting to "/"
		}

	}

}

What’s the best way to handle this problem ?

You can create a struct containing all the data required for the page to render and pass that to the template. Each template can use different fields of the struct. For example:

type data struct {
    Username string
    // other fields
}
// ...
tpl.ExecuteTemplate(w, "home", data{Username: username})

And in your template:

"logged in as" {{ .Username }}

This way, each template can use just the part of the data it needs.

I also recommend to have a look at using the block template action for easier organization of your templates.

1 Like

Thanks a lot sir , you are really helping me a lot. And on my other questions. I Very much appreciate it.

1 Like

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