gods/examples/customcomparator.go

package examples

import (
	"fmt"
	"github.com/emirpasic/gods/sets/treeset"
)

type User struct {
	id   int
	name string
}

// Comparator function (sort by IDs)
func byID(a, b interface{}) int {

	// Type assertion, program will panic if this is not respected
	c1 := a.(User)
	c2 := b.(User)

	switch {
	case c1.id > c2.id:
		return 1
	case c1.id < c2.id:
		return -1
	default:
		return 0
	}
}

func exampleCustomComparator() {
	set := treeset.NewWith(byID)

	set.Add(User{2, "Second"})
	set.Add(User{3, "Third"})
	set.Add(User{1, "First"})
	set.Add(User{4, "Fourth"})

	fmt.Println(set) // {1 First}, {2 Second}, {3 Third}, {4 Fourth}
}