1 // Copyright 2011 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package sort_test 6 7 import ( 8 "fmt" 9 "sort" 10 ) 11 12 type Person struct { 13 Name string 14 Age int 15 } 16 17 func (p Person) String() string { 18 return fmt.Sprintf("%s: %d", p.Name, p.Age) 19 } 20 21 // ByAge implements sort.Interface for []Person based on 22 // the Age field. 23 type ByAge []Person 24 25 func (a ByAge) Len() int { return len(a) } 26 func (a ByAge) Swap(i, j int) { a[i], a[j] = a[j], a[i] } 27 func (a ByAge) Less(i, j int) bool { return a[i].Age < a[j].Age } 28 29 func Example() { 30 people := []Person{ 31 {"Bob", 31}, 32 {"John", 42}, 33 {"Michael", 17}, 34 {"Jenny", 26}, 35 } 36 37 fmt.Println(people) 38 // There are two ways to sort a slice. First, one can define 39 // a set of methods for the slice type, as with ByAge, and 40 // call sort.Sort. In this first example we use that technique. 41 sort.Sort(ByAge(people)) 42 fmt.Println(people) 43 44 // The other way is to use sort.Slice with a custom Less 45 // function, which can be provided as a closure. In this 46 // case no methods are needed. (And if they exist, they 47 // are ignored.) Here we re-sort in reverse order: compare 48 // the closure with ByAge.Less. 49 sort.Slice(people, func(i, j int) bool { 50 return people[i].Age > people[j].Age 51 }) 52 fmt.Println(people) 53 54 // Output: 55 // [Bob: 31 John: 42 Michael: 17 Jenny: 26] 56 // [Michael: 17 Jenny: 26 Bob: 31 John: 42] 57 // [John: 42 Bob: 31 Jenny: 26 Michael: 17] 58 } 59
