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sort.Sort() interface in GoLang

原文：https://medium.com/@kdnotes/sort-sort-interface-in-golang-1d263d96956d

package main
import (
 "fmt"
 "sort"
 //"unicode/utf8"
)
type P struct {
 name string
 age  int
}
type nameSortedPs []P
func (a nameSortedPs) Len() int {
 return len(a)
}
func (a nameSortedPs) Less(i, j int) bool {
 //iRune, _ := utf8.DecodeRuneInString(a[i].name)
 //jRune, _ := utf8.DecodeRuneInString(a[j].name)
 //return int32(iRune) < int32(jRune)
  return a[i].age > a[j].age
}
func (a nameSortedPs) Swap(i, j int) {
 a[i], a[j] = a[j], a[i]
}
func main() {
 groupA := []P{
  {"gold", 14}, {"dave", 18}, {"kane", 12}, {"rain", 34},
 }
 sort.Sort(nameSortedPs(groupA))
fmt.Println(groupA)
}

------------------------------

Sorting is one of those tasks that comes up from time to time in software project, it important to get just the right algorithm. With the sort package from Go, the Sort interface provides an abstraction on top of commonly used sorting algorithm. That makes it very efficient and for most arbitrary sorting task.

This article briefly explores some sorting methods then explores the GoLang Sort interface in details.

Sorting in Go

sort.Ints
sort.Float64s
sort.Strings

These simple methods can be used to sot a slice of ints, float64 or strings

names := []string{“jane”, “dave”, “mike”, “kane”, “rain”}
 sort.Strings(names)
 fmt.Println(names)

We can also sort using a common comparative using the sort.Slice method, using the less (i,j) comparative function.

group := []struct {
 name string
 age int
 }{
 {“Gold”, 14}, {“dave”, 18}, {“kane”, 12}, {“rain”, 34},
 }sort.Slice(group, func(i, j int) bool {
 return group[i].age < group[j].age
 })fmt.Println(group)

The Sort interface

type Interface interface{
     Len() int
     Less (i , j) bool
     Swap(i , j int)
}

Any collection that implements this interface can be easily sorted. Len returns the length of the collection, Less receives two integers that will serve as indices from the collection, Swap implements the needed change after the Less method is called.

import (
 "fmt"
 "sort"
 "unicode/utf8"
)type P struct {
 name string
 age  int
}type nameSortedPs []Pfunc (a nameSortedPs) Len() int {
 return len(a)
}func (a nameSortedPs) Less(i, j int) bool {
 iRune, _ := utf8.DecodeRuneInString(a[i].name)
 jRune, _ := utf8.DecodeRuneInString(a[j].name)
 return int32(iRune) < int32(jRune)
}func (a nameSortedPs) Swap(i, j int) {
 a[i], a[j] = a[j], a[i]
}func main() {
 groupA := []P{
  {"gold", 14}, {"dave", 18}, {"kane", 12}, {"rain", 34},
 }
 sort.Sort(nameSortedPs(groupA))fmt.Println(groupA)
}

The user can implement any logic they wish in regards to what the sort will use to sort on.

By offering the underlying algorithm and defining the sort.Interface the programming language helps us build powerful sorting programs without enforcing a single opinion on what the algorithm should do but rather how to do it.