go随聊-map

定义map并初始化，根据key获取value

items := map[string]string{
    "id1": "1",
    "id2": "2",
    "id3": "3",
}

v:= items["id2"]
fmt.Println(v)

通过make进行构建 

items:=make(map[string]string,10)
items["id1"] = "1"
items["id2"] = "2"
items["id3"] = "3"

for k,v:=range items {
	fmt.Println(k,"=",v)
}

通过==进行赋值

items:=map[string]string{}
items["id1"] = "1"
items["id2"] = "2"
items["id3"] = "3"
fmt.Println(len(items))

通过delete删除

items:=map[string]string{}
items["id1"] = "1"
items["id2"] = "2"
items["id3"] = "3"
fmt.Println(len(items))

delete(items, "id2")
fmt.Println(len(items))

map的range遍历

items:=map[string]string{}
items["id1"] = "1"
items["id2"] = "2"
items["id3"] = "3"

for k,v:=range items {
	fmt.Println(k,"=",v)
}

判断key是否存在

items:=make(map[string]string,10)
items["id1"] = "1"
items["id2"] = "2"
items["id3"] = "3"

value,ok:=items["id4"]
if ok {
	fmt.Println(value)
}else{
	fmt.Println("不存在")
}
------------------------------
不存在

map不是线程安全的

var items=make(map[string]string,10)
func main() {
	items["id1"] = "1"
	items["id2"] = "2"
	items["id3"] = "3"
	go process()
	//遍历打印key-value值
	for{
		for k,v:=range items {
			fmt.Println(k,"=",v)
		}
	}
}

func process() {
	//一直对map进行插入、删除操作
	for {
		items["id1"]="1"
		delete(items,"id1")
	}
}
------------------------------------------------------------
fatal error: concurrent map iteration and map write