I've the below that is working fine playground
package main
import (
"html/template"
"os"
)
func main() {
tmpl := `
{{ $slice := mkSlice "a" 5 "b" }}
{{ range $slice }}
{{ . }}
{{ end }}
`
funcMap := map[string]interface{}{"mkSlice": mkSlice}
t := template.New("").Funcs(template.FuncMap(funcMap))
template.Must(t.Parse(tmpl))
t.Execute(os.Stdout, nil)
}
func mkSlice(args ...interface{}) []interface{} {
return args
}
But once I tried to run in from template file, nothing had been displayed, and no error had been recieved!
func mkSlice(args ...interface{}) []interface{} { // to ceate the array in the template
return args
}
funcMap := map[string]interface{}{"mkSlice": mkSlice}
tmpl := template.New("").Funcs(template.FuncMap(funcMap))
template.Must(tmpl.ParseFiles("index.html"))
tmpl.Execute(w, nil)
And index.html is:
{{ $slice := mkSlice "a" 5 "b" }}
{{ range $slice }}
<span> {{ . }} </span>
{{ end }}
any thought?
You don't see any errors because you don't check the error returned by tmpl.Execute(w, nil). When do check it:
if err := t.Execute(os.Stdout, nil); err != nil {
panic(err)
}
You'll see an output like:
panic: template: "" is an incomplete or empty template
The difference is that in the first case you used Template.Parse() method which:
... parses text as a template body for t.
Note that the template text you parse will be used for t itself!
In the second case you used Template.ParseFiles() which:
... parses the named files and associates the resulting templates with t. If an error occurs, parsing stops and the returned template is nil; otherwise it is t. There must be at least one file. Since the templates created by ParseFiles are named by the base names of the argument files, t should usually have the name of one of the (base) names of the files.
So in your first example t contains a single template, and that single template will be executed by Template.Execute().
In your second example t contains multiple associated templates, t itself being an empty template, and another, associated template named index.html. You may execute that template using Template.ExecuteTemplate():
if err := t.ExecuteTemplate(os.Stdout, "index.html", nil); err != nil {
panic(err)
}
For more information, see: