[non-pointer struct].<Method with pointer receiver> cannot be invoked
directly in a template.
package main
import (
"fmt"
"bytes"
"html/template"
)
type Wrapper struct {
raw []int
}
func (w *Wrapper) IsZero() bool {
if len(w.raw) == 0{
return true
}
return false
}
var tmplText = `
{{.IsZero}}
`
var tmpl = template.Must(template.New("test").Parse(tmplText))
func main() {
wrapped := Wrapper{}
fmt.Println(wrapped.IsZero())
buff := &bytes.Buffer{}
if err := tmpl.Execute(buff, wrapped); err != nil {
panic(err)
}
fmt.Println(buff.String())
}
Will produce:
panic: template: test:2:3: executing "test" at <.IsZero>: can't evaluate field
IsZero in type main.Wrapper
goroutine 1 [running]:
main.main()
/tmp/sandbox009718456/prog.go:33 +0x200
However, changing wrapped from Wrapper to a *Wrapper will work.
https://play.golang.org/p/lviUVF770c2
Again this might be expected, but I found it a surprised (because I can
clearly call the method outside the template). In my real life case, this
was layers deep in a structs I had to unpack and experiment with to find
the cause.
The error wasn't clear as to why this was happening, I could not find
documentation within template to hint at a limitation (maybe I missed it or
I did not interpret the meaning of something correctly).
What I'm looking from this post:
- Are my assumptions correct or is the proof above invalid
- If the proof is valid, is this expected behavior?
- If expected, is there documentation for this?
- and, can we see a way to have better error output, I know this is
probably difficult due to trying to reflect on what is a field vs a method
when something can't be found
Also, trying to document the error here so it gets picked up in Google when
looking for this error condition, as I was unable to find anything similar.
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