将一个模板渲染到另一个模板中，而无需每次都对其进行解析

Question

I have three templates like this:

base.html:

<h1>Base.html rendered here</h1>
{{template "content" .}}

view.html:

{{define "content"}}
...
{{end}}

edit.html:

{{define "content"}}
...
{{end}}

I store them in folder "templates".

What i want is to dynamically change template which will be rendered in {{template "content" .}} place, without parsing every time. So what i DO NOT want is this :

func main() {
   http.HandleFunc("/edit", handlerEdit)
   http.HandleFunc("/view", handlerView)
   http.ListenAndServe(":8080", nil)
}
func handlerView(w http.ResponseWriter, req *http.Request) {
   renderTemplate(w, req, "view")
}

func handlerEdit(w http.ResponseWriter, req *http.Request) {
   renderTemplate(w, req, "edit")
}

func renderTemplate(w http.ResponseWriter, req *http.Request, tmpl    string) {
   templates, err := template.ParseFiles("templates/base.html",  "templates/"+tmpl+".html")
   if err != nil {
       fmt.Println("Something goes wrong ", err)
       return
   }
   someData := &Page{Title: "QWE", Body: []byte("sample body")}
   templates.Execute(w, someData)
}

I was looking at the template.ParseGlobe(), in order to do something like this

var templates = template.Must(template.ParseGlob("templates/*.html"))
... //and then somthing like this:
err := templates.ExecuteTemplate(w, tmpl+".html", p)

But ExecuteTamplate() recieves only one string as template's name. How in this case i can render two and more templates?

Answer 1

Instead of writing directly to the http.ResponseWriter on your call to ExecuteTemplate, write to a byte buffer and send that through the call to the next template by prepping it with a template.HTML call.

var b bytes.Buffer

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

err := templates.ExecuteTemplate(b, templ_1, p)
if err != nil { //handle err }
err := templates.ExecuteTemplate(w, templ_2, template.HTML(b.String()))
if err != nil { //handle err }

If you're going to use an unknown number of templates, you can capture the intermediate step with a string:

var strtmp string
err := templates.ExecuteTemplate(b, templ_1, p)
if err != nil { //handle err }

strtemp = b.String()  //store the output
b.Reset()             //prep buffer for next template's output

err := templates.ExecuteTemplate(b, templ_2, template.HTML(strtmp))
if err != nil { //handle err }

//... until all templates are applied

b.WriteTo(w)  //Send the final output to the ResponseWriter

EDIT: As @Zhuharev pointed out, if the composition of the view and edit templates are fixed, they can both reference base rather than base trying to provide a reference to either view or edit:

{{define "viewContent"}}
{{template "templates/base.html" .}}
...Current view.html template...
{{end}}

{{define "editContent"}}
{{template "templates/base.html" .}}
...Current edit.html template...
{{end}}