struct
我們可以聲明新的類(lèi)型，作為其它類(lèi)型的屬性或字段容器。
如，創(chuàng)建一個(gè)自定義類(lèi)型person代表一個(gè)人的實(shí)體。這個(gè)實(shí)體擁有屬性：姓名&年齡。這樣的類(lèi)型我們稱(chēng)之為struct。
type person struct{
name string
age int
}
var P person // P 現(xiàn)在就是 person 類(lèi)型的變量了
P.name = "Astaxie" // 賦值 "Astaxie" 給 P 的 name 屬性 .
P.age = 25 // 賦值 "25" 給變量 P 的 age 屬性
fmt.Printf("The person's name is %s", P.name) // 訪(fǎng)問(wèn) P 的 name 屬性 .
除了上面這種P的聲明使用之外，還有其他兩種聲明使用方式
1、按照順序提供初始化值
P := person{"Liuxinming", 28}
2、通過(guò)field:value的方式初始化，這樣可以任意順序
P := person{age:28, name:"Liuxinming"}
舉例：
package main
import "fmt"
//聲明一個(gè)新的類(lèi)型
type person struct {
name string
avg int
}
//比較兩個(gè)人的年齡，返回年齡大的那個(gè)人，并且返回年齡差
//struct 也是傳值的
func older(p1, p2 person) (person, int) {
if p1.avg > p2.avg { //比較p1和p2年齡
return p1, p1.avg - p2.avg
}
return p2, p2.avg - p1.avg
}
func main() {
var tom person
//賦值初始化
tom.name, tom.avg = "Tom", 18
//兩個(gè)字段都寫(xiě)清楚的初始化
bob := person{avg: 25, name: "Bob"}
//按照struct定義順序初始化
paul := person{"Paul", 43}
tb_Older, tb_diff := older(tom, bob)
tp_Older, tp_diff := older(tom, paul)
bp_Older, bp_diff := older(bob, paul)
fmt.Printf("Of %s and %s, %s is older by %d years/n",
tom.name, bob.name, tb_Older.name, tb_diff)
fmt.Printf("Of %s and %s, %s is older by %d years/n",
tom.name, paul.name, tp_Older.name, tp_diff)
fmt.Printf("Of %s and %s, %s is older by %d years/n",
bob.name, paul.name, bp_Older.name, bp_diff)
}
輸出結(jié)果如下：
Of Tom and Bob, Bob is older by 7 years
Of Tom and Paul, Paul is older by 25 years
Of Bob and Paul, Paul is older by 18 years
struct的匿名字段
我們上面介紹了如何定義一個(gè)struct,定義的時(shí)候是字段名與其類(lèi)型一一對(duì)應(yīng)，實(shí)際上Go支持只提供類(lèi)型，而不寫(xiě)字段名的方式，也就是匿名字段，也稱(chēng)為嵌入字段。
當(dāng)匿名字段是一個(gè)struct的時(shí)候，那么這個(gè)struct所擁有的全部字段都被隱式地引入了當(dāng)前定義的這個(gè)struct：
// struct2.go
package main
import (
"fmt"
)
type Human struct {
name string
age int
weight int
}
type Student struct {
Human //匿名字段，那么默認(rèn)struct就包含了Human所有字段
speciality string
}
func main() {
//初始化一個(gè)學(xué)生
mark := Student{Human{"Mark", 25, 100}, "Computer Science"}
//訪(fǎng)問(wèn)相應(yīng)的字段
fmt.Println("His name is ", mark.name)
fmt.Println("His age is ", mark.age)
fmt.Println("His weight is ", mark.weight)
fmt.Println("His speciality is ", mark.speciality)
//修改對(duì)應(yīng)的信息
mark.speciality = "AI"
fmt.Println("Mark changed his speciality")
fmt.Println("His speciality is ", mark.speciality)
// 修改他的年齡信息
fmt.Println("Mark become old")
mark.age = 46
fmt.Println("His age is", mark.age)
// 修改他的體重信息
fmt.Println("Mark is not an athlet anymore")
mark.weight += 60
fmt.Println("His weight is", mark.weight)
}
輸出結(jié)果：
His name is Mark
His age is 25
His weight is 100
His speciality is Computer Science
Mark changed his speciality
His speciality is AI
Mark become old
His age is 46
Mark is not an athlet anymore
His weight is 160
