golang - how to split string in template

Question

I try to use template.FuncMap but there are panic error

panic: runtime error: invalid memory address or nil pointer dereference

code:

type Article struct{
    Id int
    Title string
    Tags  string
}

var (
    tplFuncMap template.FuncMap 
)

func main() {
    article := &Article{Id:1, Title:"hello world", Tags:"golang,javascript"}
    tplFuncMap =  make(template.FuncMap)
    tplFuncMap["Split"] = Split
    tpl, _ := template.ParseFiles("a.html", "b.html")
    tpl = tpl.Funcs(tplFuncMap)
    tpl.Execute(os.Stdout, article)
}

func Split(s string, d string) []string {
    arr := strings.Split(s, d)
    return arr
}

a.html

//i want to split tags and range
{{$arr := Split .Tags ","}}
{{range $k, $v := $arr}}
    <a href="{{$v}}">{{$v}}</a>
{{end}}

Thanks.

Answer 1

You are ignoring the error returned by template.ParseFiles, that will probably tell you your problem. ParseFiles is probably throwing an error because the function Split isn't defined when you parse the template. Never ignore errors.

Edit

To make it work, do something like this:

tplFuncMap =  make(template.FuncMap)  
tplFuncMap["Split"] = Split  
tmpl, err = template.New("").Funcs(tplFuncMap).ParseFiles("a.html", "b.html")

The difference is that the FuncMap is defined before the templates are parsed.