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Source file src/sort/example_interface_test.go

Documentation: sort

  // Copyright 2011 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package sort_test
  
  import (
  	"fmt"
  	"sort"
  )
  
  type Person struct {
  	Name string
  	Age  int
  }
  
  func (p Person) String() string {
  	return fmt.Sprintf("%s: %d", p.Name, p.Age)
  }
  
  // ByAge implements sort.Interface for []Person based on
  // the Age field.
  type ByAge []Person
  
  func (a ByAge) Len() int           { return len(a) }
  func (a ByAge) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
  func (a ByAge) Less(i, j int) bool { return a[i].Age < a[j].Age }
  
  func Example() {
  	people := []Person{
  		{"Bob", 31},
  		{"John", 42},
  		{"Michael", 17},
  		{"Jenny", 26},
  	}
  
  	fmt.Println(people)
  	// There are two ways to sort a slice. First, one can define
  	// a set of methods for the slice type, as with ByAge, and
  	// call sort.Sort. In this first example we use that technique.
  	sort.Sort(ByAge(people))
  	fmt.Println(people)
  
  	// The other way is to use sort.Slice with a custom Less
  	// function, which can be provided as a closure. In this
  	// case no methods are needed. (And if they exist, they
  	// are ignored.) Here we re-sort in reverse order: compare
  	// the closure with ByAge.Less.
  	sort.Slice(people, func(i, j int) bool {
  		return people[i].Age > people[j].Age
  	})
  	fmt.Println(people)
  
  	// Output:
  	// [Bob: 31 John: 42 Michael: 17 Jenny: 26]
  	// [Michael: 17 Jenny: 26 Bob: 31 John: 42]
  	// [John: 42 Bob: 31 Jenny: 26 Michael: 17]
  }
  

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