map介绍
map是key-value数据结构,又称为字段或者关联数组,类似其他编程语言的集合,在编程中经常使用到。
基本语法
var map(变量名称)map[keytype]valuetype
golang中的map的key可以是很多类型,比如bool,数字,string,指针,channel,还可以是只包含前面几个类型的接口,结构体,数组
通常为int,string
注意:
slice,map还有function不可以,因为这几个没法用==来判断
注意:map声明是不会分配内存的,初始化需要make,分配内存后才能赋值和使用
func main() {
var a map[string]string
a = make(map[string]string,10)
a["name1"] = "宋江"
a["name2"] = "张飞"
fmt.Println(a)
cites := make(map[string]string)
cites["name1"] = "北京"
cites["name2"] = "天津"
cites["name3"] = "上海"
fmt.Println(cites)
heroes := map[string]string{
"hero1" : "吴用",
"hero2" : "宋江",
}
fmt.Println(heroes)
}
实例:存放三个学生信息,每个学生有name和sex信息
student := make(map[string]map[string]string)
student["stu1"] = make(map[string]string,2)
student["stu1"]["name"] = "tom"
student["stu1"]["sex"] = "男"
student["stu2"] = make(map[string]string,2)
student["stu2"]["name"] = "tony"
student["stu2"]["sex"] = "男"
student["stu3"] = make(map[string]string,2)
student["stu3"]["name"] = "mary"
student["stu3"]["sex"] = "女"
fmt.Println(student)
delete(a,"name1")
fmt.Println(a)
val,ok := a["name2"]
if ok{
fmt.Printf("有,值为%v\n",val)
}else {
fmt.Printf("没有\n")
}
for k,v := range cites{
fmt.Printf("k = %v v = %v\n",k,v)
}
//切片的使用
monsters := make([]map[string]string,2)
if monsters[0] == nil{
monsters[0] = make(map[string]string,2)
monsters[0]["name"] = "牛魔王"
monsters[0]["age"] = "500"
}
if monsters[1] == nil{
monsters[1] = make(map[string]string,2)
monsters[1]["name"] = "白骨精"
monsters[1]["age"] = "1000"
}
//使用切片的append函数,可以动态的增加monster
newmonsters := map[string]string{
"name" : "玉兔精",
"age" : "600",
}
monsters = append(monsters,newmonsters)
fmt.Println(monsters)
type stu struct {
Name string
Age int
Address string
}
func main() {
students := make(map[string]stu,10)
stu1 := stu{"a",18,"西安"}
stu2 := stu{"b",19,"天津"}
students["num1"] = stu1
students["num2"] = stu2
fmt.Println(students)
}
面向对象
type Cat struct {
Name string
Age string
Color string
}
type Person struct{
Name string
Age string
arr *int
slice []int
map1 map[string]string
}
func main() {
var a Person
//在使用slice之前,一定要用make
a.slice = make([]int,10)
a.slice[0] = 100
//在使用map之前,一定要用make
a.map1 = make(map[string]string)
a.map1["数学"] = "120"
fmt.Println(a)
var b *Person = new(Person)
//因为b是一个指针,因此标准的给字段赋值的方式如下
b.Name = "smith"
b.Age = 30
fmt.Println(b)
var cat1 Cat
cat1.Name = "小白"
cat1.Age = "10"
cat1.Color = "白色"
fmt.Println(cat1)
}
type Monster struct {
Name string `json:"name"`
Age int `json:"age"`
Skill string `json:"skill"`
}
func main() {
monster := Monster{"牛魔王",2000,"芭蕉扇"}
//将monster变量序列化为json格式字符串
jsonmonster,_:= json.Marshal(monster)
fmt.Println(string(jsonmonster))
}