How to pass just a variable (not a struct member) into text/html template. Golang

Asked 15/1, 2015 at 19:16 Answered 23/8, 2015 at 12:39

is there any way to pass just a variable (string, int, bool) into template. For example (something similar):

import (
    "html/template"
)

func main() {
    ....
    tmpl := template.Must(template.ParseFiles("templates/index.html"))
    mux.HandleFunc("/", func(rw http.ResponseWriter, req *http.Request) {
        varmap := map[string]interface{}{
            "var1": "value",
            "var2": 100,
        }
        tmpl.ExecuteTemplate(rw, "index", varmap)
    })

    // content of index.html
    {{define "index"}}
    {{var1}} is equal to {{var2}}
    {{end}}
}

Marrowfat answered 15/1, 2015 at 19:16 Comment(0)

Yes just use the dot in front of it:

http://play.golang.org/p/7NXu9SDiik

package main

import (
    "html/template"
    "log"
    "os"
)

var tmplString = `    // content of index.html
    {{define "index"}}
    {{.var1}} is equal to {{.var2}}
    {{end}}
`

func main() {
    tmpl, err := template.New("test").Parse(tmplString)
    if err != nil {
        log.Fatal(err)
    }
    varmap := map[string]interface{}{
        "var1": "value",
        "var2": 100,
    }
    tmpl.ExecuteTemplate(os.Stdout, "index", varmap)

}

Cufic answered 15/1, 2015 at 19:25 Comment(0)

It is possible to pass just a simple value of any type. If you do so, you can refer to it in the template as {{.}}.

Here is an example (try it on the Go Playgound):

s := "<html><body>Value passed: {{.}}</body></html>\n"

tmpl := template.Must(template.New("test").Parse(s))

tmpl.Execute(os.Stdout, false)
tmpl.Execute(os.Stdout, 1)
tmpl.Execute(os.Stdout, "me")

Output:

<html><body>Value passed: false</body></html>
<html><body>Value passed: 1</body></html>
<html><body>Value passed: me</body></html>

Castera answered 15/1, 2015 at 19:24 Comment(7)

But what if I want also to pass a struct with some variables? Is it possible? – Marrowfat 15/1, 2015 at 19:27

@TimurFayzrakhmanov Then you should add the extra value to your struct, or create a new wrapper struct or add both the struct and the extra value to a map. You can only specify one value, but that one value can be a wrapper of arbitrary many other values. – Castera 15/1, 2015 at 19:29

What about this? varmap := map[string]interface{}{ "var1": "value", "var2": 100, "var3": Struct }, Then call the struct members by .var3.StructMember ? – Marrowfat 15/1, 2015 at 19:34

@TimurFayzrakhmanov Yes, in that case you could refer to it by .var3.StructMember. – Castera 15/1, 2015 at 19:35

@TimurFayzrakhmanov Just so you know this "serial upvoting" is referred to as voting fraud and is not allowed on Stack Overflow. And it is automatically detected and undone. – Castera 16/1, 2015 at 3:40

sad (...I thought as much, but still it's quite logical behavior. – Marrowfat 16/1, 2015 at 7:26

@TimurFayzrakhmanov your comment was helpful in terms of bundling an existing struct, and some extra values for populating input fields. – Narthex 27/3, 2018 at 23:30

Try fasttemplate [1]. It accepts a map of placeholders' substitution values. And it works faster than html/template on simple templates.

[1] http://github.com/valyala/fasttemplate

Paluas answered 23/8, 2015 at 12:39 Comment(0)

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