编程语言13、GO语言没有类-GOLANG
xiugo语言不支持类和对象，也不支持继承，但是通过go提供的结构和方法可以实现面向对象设计的概念
绑定方法到结构
DMS格式，度，分，秒表示坐标，每60秒为一分，每60分为一度，编写一个decimal()方法实现将坐标转换为十进制单位为度
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| package main
import "fmt"
type coordinate struct {
d, m, s float64
h rune
}
func (c coordinate) decimal() float64 {
sign := 1.0
switch c.h {
case 'S', 'W', 's', 'w':
sign = -1
}
return sign * (c.d + c.m/60 + c.s/3600)
}
func main() {
lat := coordinate{4, 35, 22.2, 'S'}
long := coordinate{137, 26, 30.12, 'E'}
fmt.Println("纬度:", lat.decimal(), "经度:", long.decimal())
}
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构造函数
初始化结构的同时将经纬度转换为更友好的十进制单位
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| package main
import "fmt"
type coordinate struct {
d, m, s float64
h rune
}
type location struct {
lat, long float64
}
func (c coordinate) decimal() float64 {
sign := 1.0
switch c.h {
case 'S', 'W', 's', 'w':
sign = -1
}
return sign * (c.d + c.m/60 + c.s/3600)
}
func main() {
lat1 := coordinate{4, 35, 22.2, 'S'}
long1 := coordinate{137, 26, 30.12, 'E'}
curiosity := location{lat1.decimal(), long1.decimal()}
fmt.Println(curiosity)
}
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go语言没有提供专用的构造方法，但是在约定俗成的函数名称以New，new关键字开头的函数一般是初始化某个类型的构造函数
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| package main
import "fmt"
type coordinate struct {
d, m, s float64
h rune
}
type location struct {
lat, long float64
}
func (c coordinate) decimal() float64 {
sign := 1.0
switch c.h {
case 'S', 'W', 's', 'w':
sign = -1
}
return sign * (c.d + c.m/60 + c.s/3600)
}
func newLocation(lat, long coordinate) location {
return location{lat.decimal(), long.decimal()}
}
func main() {
curiosity := newLocation(coordinate{4, 35, 22.2, 'S'}, coordinate{137, 26, 30.12, 'E'})
fmt.Println(curiosity)
}
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类的替代品
go语言通过结构和方法来满足传统编程语言的类的需求
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| package main
import (
"fmt"
"math"
)
type location struct {
lat, long float64
}
type world struct {
radius float64
}
func (w world) distance(p1, p2 location) float64 {
s1, c1 := math.Sincos(rad(p1.lat))
s2, c2 := math.Sincos(rad(p2.lat))
clong := math.Cos(rad(p1.long - p2.long))
return w.radius * math.Acos(s1*s2+c1*c2*clong)
}
func rad(deg float64) float64 {
return deg * math.Pi / 180
}
func main() {
var mars = world{radius: 3389.5}
spirit := location{-14.5684, 175.472636}
opportunity := location{-1.9462, 354.4734}
dist := mars.distance(spirit, opportunity)
fmt.Printf("%f km\n", dist)
}
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