Go Flat Yourself

[RCHowell]

This is a library to flat map Go structs.

Library code

Background

I was writing an API client for a service which expected query strings and returned XML. I wanted to define each type of request's input and output as Go structs and have google/go-querystring and encoding/xml handle (un)marshaling.

The encoding/xml package worked for my purposes, but the google/go-querystring did not format nested keys as the service expected. I could have sent a PR to google/go-querystring, but this was not feasible for reasons unrelated to that package -- nonetheless, it's a good package with a fair number of options for output format.

Flat mapping Go structs is a fairly straightforward exercise with Go reflection and writing fewer than 100 lines-of-code was the path of least resistance. This library is slightly more general than google/go-querystring because it will output a string map rather than query params and will accept primitives in addition to structs.

Example

type AStruct struct {
    A string
    B []string
    C CStruct
}

type CStruct struct {
    D int
    E bool
}

s := &AStruct{
    A: "hello",
    B: []string{"x", "y", "z"},
    C: CStruct{
        D: 7,
        E: true,
    },
}

o := flat.Flatten(s)

// value of `o`
//   map[string]string{
//     "A": "hello",
//     "B.0": "x",
//     "B.1": "y",
//     "B.2": "z",
//     "C.D": "7",
//     "C.E": "true",
//   }

Notes

• It will print values of pointers
• If given a primitive of type p with value v, Flatten returns {"p": "v"}