我只是有一个问题，我有一个数组的结构体，例如。
package main
import "log"
type Planet struct {
Name string `json:"name"`
Aphelion float64 `json:"aphelion"` // in million km
Perihelion float64 `json:"perihelion"` // in million km
Axis int64 `json:"Axis"` // in km
Radius float64 `json:"radius"`
}
func main() {
var mars = new(Planet)
mars.Name = "Mars"
mars.Aphelion = 249.2
mars.Perihelion = 206.7
mars.Axis = 227939100
mars.Radius = 3389.5
var earth = new(Planet)
earth.Name = "Earth"
earth.Aphelion = 151.930
earth.Perihelion = 147.095
earth.Axis = 149598261
earth.Radius = 6371.0
var venus = new(Planet)
venus.Name = "Venus"
venus.Aphelion = 108.939
venus.Perihelion = 107.477
venus.Axis = 108208000
venus.Radius = 6051.8
planets := [...]Planet{*mars, *venus, *earth}
log.Println(planets)
}
假设你想按Axis排序。你是怎么做到的?
(注:我已经看到http://golang.org/pkg/sort/，它似乎工作，但我必须添加大约20行，只是为了通过一个非常简单的键进行简单的排序。我有一个python背景，它就像排序一样简单(行星，键=lambda n: n. axis) -在Go中有类似的简单吗?)
这里还有另一种方法来减少一些锅炉板。免责声明，它使用反射和损失类型安全。
这里是一个演示
所有神奇的事情都发生在Prop函数中。它接受要排序的struct属性和排序顺序(升序、降序)，并返回执行比较的函数。
package main
import (
"log"
"reflect"
"sort"
)
func test(planets []Planet) {
log.Println("Sort Name")
By(Prop("Name", true)).Sort(planets)
log.Println(planets)
log.Println("Sort Aphelion")
By(Prop("Aphelion", true)).Sort(planets)
log.Println(planets)
log.Println("Sort Perihelion")
By(Prop("Perihelion", true)).Sort(planets)
log.Println(planets)
log.Println("Sort Axis")
By(Prop("Axis", true)).Sort(planets)
log.Println(planets)
log.Println("Sort Radius")
By(Prop("Radius", true)).Sort(planets)
log.Println(planets)
}
func Prop(field string, asc bool) func(p1, p2 *Planet) bool {
return func(p1, p2 *Planet) bool {
v1 := reflect.Indirect(reflect.ValueOf(p1)).FieldByName(field)
v2 := reflect.Indirect(reflect.ValueOf(p2)).FieldByName(field)
ret := false
switch v1.Kind() {
case reflect.Int64:
ret = int64(v1.Int()) < int64(v2.Int())
case reflect.Float64:
ret = float64(v1.Float()) < float64(v2.Float())
case reflect.String:
ret = string(v1.String()) < string(v2.String())
}
if asc {
return ret
}
return !ret
}
}
type Planet struct {
Name string `json:"name"`
Aphelion float64 `json:"aphelion"` // in million km
Perihelion float64 `json:"perihelion"` // in million km
Axis int64 `json:"Axis"` // in km
Radius float64 `json:"radius"`
}
type By func(p1, p2 *Planet) bool
func (by By) Sort(planets []Planet) {
ps := &planetSorter{
planets: planets,
by: by, // The Sort method's receiver is the function (closure) that defines the sort order.
}
sort.Sort(ps)
}
type planetSorter struct {
planets []Planet
by func(p1, p2 *Planet) bool // Closure used in the Less method.
}
// Len is part of sort.Interface.
func (s *planetSorter) Len() int { return len(s.planets) }
// Swap is part of sort.Interface.
func (s *planetSorter) Swap(i, j int) {
s.planets[i], s.planets[j] = s.planets[j], s.planets[i]
}
// Less is part of sort.Interface. It is implemented by calling the "by" closure in the sorter.
func (s *planetSorter) Less(i, j int) bool {
return s.by(&s.planets[i], &s.planets[j])
}
func main() {
test(dataSet())
}
func dataSet() []Planet {
var mars = new(Planet)
mars.Name = "Mars"
mars.Aphelion = 249.2
mars.Perihelion = 206.7
mars.Axis = 227939100
mars.Radius = 3389.5
var earth = new(Planet)
earth.Name = "Earth"
earth.Aphelion = 151.930
earth.Perihelion = 147.095
earth.Axis = 149598261
earth.Radius = 6371.0
var venus = new(Planet)
venus.Name = "Venus"
venus.Aphelion = 108.939
venus.Perihelion = 107.477
venus.Axis = 108208000
venus.Radius = 6051.8
return []Planet{*mars, *venus, *earth}
}
这里还有另一种方法来减少一些锅炉板。免责声明，它使用反射和损失类型安全。
这里是一个演示
所有神奇的事情都发生在Prop函数中。它接受要排序的struct属性和排序顺序(升序、降序)，并返回执行比较的函数。
package main
import (
"log"
"reflect"
"sort"
)
func test(planets []Planet) {
log.Println("Sort Name")
By(Prop("Name", true)).Sort(planets)
log.Println(planets)
log.Println("Sort Aphelion")
By(Prop("Aphelion", true)).Sort(planets)
log.Println(planets)
log.Println("Sort Perihelion")
By(Prop("Perihelion", true)).Sort(planets)
log.Println(planets)
log.Println("Sort Axis")
By(Prop("Axis", true)).Sort(planets)
log.Println(planets)
log.Println("Sort Radius")
By(Prop("Radius", true)).Sort(planets)
log.Println(planets)
}
func Prop(field string, asc bool) func(p1, p2 *Planet) bool {
return func(p1, p2 *Planet) bool {
v1 := reflect.Indirect(reflect.ValueOf(p1)).FieldByName(field)
v2 := reflect.Indirect(reflect.ValueOf(p2)).FieldByName(field)
ret := false
switch v1.Kind() {
case reflect.Int64:
ret = int64(v1.Int()) < int64(v2.Int())
case reflect.Float64:
ret = float64(v1.Float()) < float64(v2.Float())
case reflect.String:
ret = string(v1.String()) < string(v2.String())
}
if asc {
return ret
}
return !ret
}
}
type Planet struct {
Name string `json:"name"`
Aphelion float64 `json:"aphelion"` // in million km
Perihelion float64 `json:"perihelion"` // in million km
Axis int64 `json:"Axis"` // in km
Radius float64 `json:"radius"`
}
type By func(p1, p2 *Planet) bool
func (by By) Sort(planets []Planet) {
ps := &planetSorter{
planets: planets,
by: by, // The Sort method's receiver is the function (closure) that defines the sort order.
}
sort.Sort(ps)
}
type planetSorter struct {
planets []Planet
by func(p1, p2 *Planet) bool // Closure used in the Less method.
}
// Len is part of sort.Interface.
func (s *planetSorter) Len() int { return len(s.planets) }
// Swap is part of sort.Interface.
func (s *planetSorter) Swap(i, j int) {
s.planets[i], s.planets[j] = s.planets[j], s.planets[i]
}
// Less is part of sort.Interface. It is implemented by calling the "by" closure in the sorter.
func (s *planetSorter) Less(i, j int) bool {
return s.by(&s.planets[i], &s.planets[j])
}
func main() {
test(dataSet())
}
func dataSet() []Planet {
var mars = new(Planet)
mars.Name = "Mars"
mars.Aphelion = 249.2
mars.Perihelion = 206.7
mars.Axis = 227939100
mars.Radius = 3389.5
var earth = new(Planet)
earth.Name = "Earth"
earth.Aphelion = 151.930
earth.Perihelion = 147.095
earth.Axis = 149598261
earth.Radius = 6371.0
var venus = new(Planet)
venus.Name = "Venus"
venus.Aphelion = 108.939
venus.Perihelion = 107.477
venus.Axis = 108208000
venus.Radius = 6051.8
return []Planet{*mars, *venus, *earth}
}
至于Go 1.8， @AndreKR的答案是更好的解决方案。
您可以实现一个实现排序接口的集合类型。
下面是两个这样的类型的例子，它们允许你通过Axis或Name进行排序:
package main
import "log"
import "sort"
// AxisSorter sorts planets by axis.
type AxisSorter []Planet
func (a AxisSorter) Len() int { return len(a) }
func (a AxisSorter) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
func (a AxisSorter) Less(i, j int) bool { return a[i].Axis < a[j].Axis }
// NameSorter sorts planets by name.
type NameSorter []Planet
func (a NameSorter) Len() int { return len(a) }
func (a NameSorter) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
func (a NameSorter) Less(i, j int) bool { return a[i].Name < a[j].Name }
type Planet struct {
Name string `json:"name"`
Aphelion float64 `json:"aphelion"` // in million km
Perihelion float64 `json:"perihelion"` // in million km
Axis int64 `json:"Axis"` // in km
Radius float64 `json:"radius"`
}
func main() {
var mars Planet
mars.Name = "Mars"
mars.Aphelion = 249.2
mars.Perihelion = 206.7
mars.Axis = 227939100
mars.Radius = 3389.5
var earth Planet
earth.Name = "Earth"
earth.Aphelion = 151.930
earth.Perihelion = 147.095
earth.Axis = 149598261
earth.Radius = 6371.0
var venus Planet
venus.Name = "Venus"
venus.Aphelion = 108.939
venus.Perihelion = 107.477
venus.Axis = 108208000
venus.Radius = 6051.8
planets := []Planet{mars, venus, earth}
log.Println("unsorted:", planets)
sort.Sort(AxisSorter(planets))
log.Println("by axis:", planets)
sort.Sort(NameSorter(planets))
log.Println("by name:", planets)
}
更新:这个答案与旧版本的go有关。对于Go 1.8和更新版本，请参阅上面AndreKR的答案。
如果您想要一些比标准库排序包更简洁的包，您可以使用第三方的github.com/bradfitz/slice包。它使用了一些技巧来生成排序切片所需的Len和Swap方法，因此您只需要提供一个Less方法。
使用这个包，你可以执行排序:
slice.Sort(planets[:], func(i, j int) bool {
return planets[i].Axis < planets[j].Axis
})
行星[:]部分是必要的，以产生一个切片覆盖你的阵列。如果你把行星做成一个切片而不是数组，你就可以跳过这个部分。
从Go 1.8开始，你就可以使用排序了。Slice对切片进行排序:
sort.Slice(planets, func(i, j int) bool {
return planets[i].Axis < planets[j].Axis
})
通常没有理由使用数组而不是切片，但在您的示例中使用的是数组，因此必须使用切片(add[:])覆盖它以使其与排序一起工作。片:
sort.Slice(planets[:], func(i, j int) bool {
return planets[i].Axis < planets[j].Axis
})
排序会改变数组，所以如果你真的想，你可以在排序后继续使用数组而不是切片。
您可以在[]Planet上实现Sort接口，而不是在包含集合和将进行比较的闭包的类型上实现Sort接口。您必须为每个属性的比较闭包提供实现。
我觉得这个方法比为结构的每个属性实现Sort类型更好。
这个答案几乎是直接从排序文档中撕下来的，所以我不能对此有太多的功劳
package main
import (
"log"
"sort"
)
type Planet struct {
Name string `json:"name"`
Aphelion float64 `json:"aphelion"` // in million km
Perihelion float64 `json:"perihelion"` // in million km
Axis int64 `json:"Axis"` // in km
Radius float64 `json:"radius"`
}
type By func(p1, p2 *Planet) bool
func (by By) Sort(planets []Planet) {
ps := &planetSorter{
planets: planets,
by: by,
}
sort.Sort(ps)
}
type planetSorter struct {
planets []Planet
by func(p1, p2 *Planet) bool
}
func (s *planetSorter) Len() int {
return len(s.planets)
}
func (s *planetSorter) Swap(i, j int) {
s.planets[i], s.planets[j] = s.planets[j], s.planets[i]
}
func (s *planetSorter) Less(i, j int) bool {
return s.by(&s.planets[i], &s.planets[j])
}
怎么称呼它呢?
func main() {
/* Same code as in the question */
planets := []Planet{*mars, *venus, *earth}
By(func(p1, p2 *Planet) bool {
return p1.Name < p2.Name
}).Sort(planets)
log.Println(planets)
By(func(p1, p2 *Planet) bool {
return p1.Axis < p2.Axis
}).Sort(planets)
log.Println(planets)
}
这里是一个演示
