Go 指南学习笔记六

1.map

map在使用之前必须使用make来创建，值为nil的map是空的，并且不能对它赋值

package main

import (
  "fmt"
)

type Vertex struct{
  Lat, Long float64
}

var m map[string]Vertex

func main() {
  m = make(map[string]Vertex)
  m["Bell Labs"] = Vertex{40.68433, -74.39967}
  fmt.Println(m["Bell Labs"])// {40.68433 -74.39967}
}

2.和结构体语法类似

var n = map[string]Vertex {
  "Bell Labs": Vertex{40.68433, -74.39967,},
  "Google":Vertex{37.42202, -122.08408,},
}
fmt.Println(n) //map[Bell Labs:{40.68433 -74.39967} Google:{37.42202 -122.08408}]

如果map的value值只是一个类型，可以在{}中将类型省略

var k = map[string]Vertex{
  "Bell Labs": {40.68433, -74.39967},
  "Google": {37.42202, -122.08408},
}

3.修改map

• 插入或者修改元素: m[key] = elem
• 获得元素: elem = m[key]
• 删除元素: delete(m,key)
• 检测是否存在: elem, ok = m[key]