07 指针和map

一、指针

&：取地址
*：根据地址取值

1.new

//申请一个内存地址
var p *int
var p1 = new(int)

fmt.Println(p)  //<nil>
fmt.Println(p1) //0xc000128058

2.make

//区别于new，只用于slice、map、channel内存创建，返回类型而不是指针
var a = make([]int, 3, 5)
var b = make(map[string]int, 10)

二、map

1.定义

//方法1
var a = make(map[string]int, 1)

//方法2
var b map[string]int
b = make(map[string]int, 10)

2.判断键是否存在

var b = make(map[string]int, 10)
b["hello"] = 1
b["world"] = 2

value, ok := b["hello"]

fmt.Println(value, ok) //1 true

3.遍历

var b = make(map[string]int, 10)
b["hello"] = 1
b["world"] = 2

for key, value := range b {
	fmt.Println(key, value) //1 true
}

4.删除元素

delete(b, "hello")