sortingbyfunctions.go

//
// gobyexample.com
// sortingbyfunctions.go
//
package main

import (
	"fmt"
	"sort"
)

//
// In order to sort by a custom function in Go,
// we need a corresponding type.
//
// Here we’ve created a byLength type that is just an
// alias for the builtin []string type.
//
type byLength []string

// We implement sort.Interface - Len, Less, and Swap - on our type
// so we can use the sort package’s generic Sort function.
//
// Len and Swap will usually be similar across types and Less will
// hold the actual custom sorting logic. In our case we want to sort
//  in order of increasing string length, so we use len(s[i]) and len(s[j]) here.
func (s byLength) Len() int {
	return len(s)
}
func (s byLength) Swap(i, j int) {
	s[i], s[j] = s[j], s[i]
}
func (s byLength) Less(i, j int) bool {
	return len(s[i]) < len(s[j])
}

// With all of this in place,
// we can now implement our custom
// sort by converting the original fruits slice to byLength,
// and then use sort.Sort on that typed slice.
func main() {
	fruits := []string{"peach", "kiwi"}
	sort.Sort(byLength(fruits))
	fmt.Println(fruits)
}