cannot call pointer method on "github.com/mholt/binding".Bind(c.Request, &form)

[troyk]

Checking out your binding lib, looks nice and I think it's going to save me a bunch of time! The README docs mention the ability to call Handle with Bind in a one-liner fashion, however (Go 1.3) I get an error. I annotated the error on the commented lines below, you can see I'm using the same exact arguments with the non-commented lines which compile fine.

Thanks again, Troy

    form := LoginForm{}

    err := binding.Bind(c.Request, &form)
    if err.Handle(c.Writer) {
        return
    }
    // causes cannot call pointer method on "github.com/mholt/binding".Bind(c.Request, &form)
    //if binding.Bind(c.Request, &form).Handle(c.Writer) {
    //  return
    //}

[mark-kubacki]

That's a subtle one! Indeed, the README is not up-to-date on this. We have to go through an assignment for this to work (your non-commented code):

form := new(LoginForm)
if errs := binding.Bind(req, form); errs.Handle(resp) {
    return
}

see http://golang.org/ref/spec#Address_operators

---

1. binding/errors.go

   Line 67 in 9e459fa

   func (e *Errors) Handle(response http.ResponseWriter) bool {

2. binding/binding.go

   Line 18 in 9e459fa

   func Bind(req *http.Request, userStruct FieldMapper) Errors {

[mholt]

Nice find. And @wmark thanks for pointing out the discrepancy.

I could change the Handle method to have a value receiver, which would enable that convenient, chained one-liner, rather than having to separate the assignment into a different statement. I tried this locally and confirmed that the example in the README still works, including that one line that is currently broken.

Making the change is simple. But I'm not sure if there are other implications of changing the receiver on that method from pointer to value. Can you think of any? If there aren't any obvious implications that I'm overlooking, I'll just make the change and resolve this issue.

[mark-kubacki]

I don't see anything relevant here. Let's do it.

[mark-kubacki]

Here's Rob Pike's comment on a related matter:

https://groups.google.com/d/msg/golang-nuts/INedfATw74A/XrIPT6gkB7kJ