The deriveKeys function returns a map's keys as a slice. It is especially useful in combination with the deriveSort function, when you want to deterministically range over a map.

Given the following input:

package keys

import (
	"strconv"
)

func printMap(m map[string]int) {
	for _, k := range deriveSort(deriveKeys(m)) {
		println(k + ":" + strconv.Itoa(m[k]))
	}
}

goderive will generate the following code:

// Code generated by goderive DO NOT EDIT.

package keys

import (
	"sort"
)

// deriveSort sorts the slice inplace and also returns it.
//
// Deprecated: In favour of generics.
func deriveSort(list []string) []string {
	sort.Strings(list)
	return list
}

// deriveKeys returns the keys of the input map as a slice.
//
// Deprecated: In favour of generics.
func deriveKeys(m map[string]int) []string {
	keys := make([]string, 0, len(m))
	for key := range m {
		keys = append(keys, key)
	}
	return keys
}