Run a function on data in a go html/template - templates

Question

I want to add hyphens (-) to a string in a go template when someone tries to save it. I'm using some modified code from the go wiki tutorial here: https://golang.org/doc/articles/wiki/
Code:
<h1>Editing {{.Title}}</h1>
<form action="/save/{{.Title}}" method="POST">
<div><input name="title" type="text" placeholder="title"></div>
<div><textarea name="body" rows="20" cols="80">{{printf "%s" .Body}}</textarea></div>
<div><input type="submit" value="Save"></div>
</form>
The line with
<form action="/save/{{.Title}}" method="POST">
is the relevant line. I need to transform .Title which might be something like "the quick brown fox" to "the-quick-brown-fox".
As you can see in the code above, you can add a function like println, but I'm not sure how I would do this for my case.

Answer 1

You can pass a template.FuncMap to the template and then you can do something like:
{{ .Title | title }}
https://play.golang.org/p/KWy_KRttD_
func Sluggify(s string) string {
return strings.ToLower(s) //for example
}
func main() {
funcMap := template.FuncMap {
"title": Sluggify,
}
tpl := template.Must(template.New("main").Funcs(funcMap).Parse(`{{define "T"}}Hello {{.Title | title }} Content: {{.Content}}{{end}}`))
tplVars := map[string]string {
"Title": "Hello world",
"Content": "Hi there",
}
tpl.ExecuteTemplate(os.Stdout, "T", tplVars)
}

Answer 2

All of your *Page structs are created by the loadPage function. So it would seem to be easiest to just create your hyphenated title then and store it in your page struct:
type Page struct {
Title string
HyphenTitle string
Body []byte
}
func loadPage(title string) (*Page, error) {
filename := title + ".txt"
body, err := ioutil.ReadFile(filename)
if err != nil {
return nil, err
}
return &Page{Title: title, Body: body, HyphenTitle: hyphenate(title)}, nil
}
func hyphenate (s string) string {
return strings.Replace(s," ","-",-1)
}
Then just use {{.HyphenTitle}} where you want it.