example_interface_test.go

Documentation: sort

		 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
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