Using reflect, is there a way to discover the type of a map key and value?

[dco...@google.com]

I am trying to write a bit of code that will take serialized data, and stuff it into an (arbitrary-ish) struct. Think taking the text output of a database query.

I know what struct the data is supposed to fit into, and I assume for this exercise that all of the data is parseable.

For Example, given:

type FRQ struct {

                Row   int

                GroupBy map[string]string

                Points []struct {

                        Timedate time.Time

                        Count    float64

                }

        }

        Rows := make([]FRQ, result.Len)

        for i := range Rows {

                Rows[i].GroupBy = make(map[string]string)

                err := result.Decode(i, &Rows[i])

                fmt.Printf("Got %v\n", Rows[i])

                if err != nil {

                        log.Fatal(err)

                }

        }

and func Decode(val interface{}, data []string) error I want to fill in Rows[i]

with a little help from an auxiliary routine to handle the time.Time conversion, I can do most of this

by walking through the struct and using reflect to figure what conversion I need from the text input.

If I cheat by knowing that GroupBy is a map[string][string] I can perform this perfectly.

But I can't see how to discover the types of the key and value of the map based the incoming interface.

I assume I'm missing something, but what?

I attach the decoder. 

Thanks,

David.

[Jesse McNelis]

On Wed, May 2, 2012 at 3:39 AM, <dco...@google.com> wrote:
> But I can't see how to discover the types of the key and value of the map
> based the incoming interface.

reflect.Type.Key() and reflect.Type.Elem() is probably what you want.

"Key() returns a map type's key type."
"Elem() returns a type's element type."
http://golang.org/pkg/reflect/#Type

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