2.Go的基本语法-指针、结构体、Map

1.指针

1.1.常规定义

func test24() {var a int = 10var b *intb = &afmt.Printf("a 的 值%d\n", a)fmt.Printf("a 的 指针地址%x\n", &a)fmt.Printf("b 的 值%d\n", *b)fmt.Printf("b 的 指针地址%x\n", b)打印var c *stringif c == nil {println("c is null")} else {println("c is not null")}
}

结果：

a 的 值10
a 的 指针地址c0001140d0
b 的 值10
b 的 指针地址c0001140d0
c is null

说明：
如果变量类型为指针，使用*b来获取值
如果类型直接是指针，使用&b获取地址

打印的时候，使用%x打印地址，使用%d打印数字，使用%s打印字符串

1.2.指针数组

func test25() {var d = [3]int{1, 2, 3}var e [3]*intfor i := 0; i < len(d); i++ {e[i] = &d[i]}for i := 0; i < len(d); i++ {fmt.Printf("d[%d] = %d\n", i, *e[i])}
}

结果：

d[0] = 1
d[1] = 2
d[2] = 3

1.3.指针的指针

func test26() {var a int = 10var b *intvar c **intb = &ac = &bfmt.Printf("b = %d\n", *b)fmt.Printf("c = %d\n", **c)
}

结果：

b = 10
c = 10

说明：
b为指针，所以获取值的时候，使用*b获取
c为指针的指针，获取值的时候，使用**c获取

1.4.指针形参

func test27() {var a = 10var b = 20c := test27V1(&a, &b)fmt.Printf("c = %d\n", c)
}func test27V1(a *int, b *int) int {return *a * *b
}

结果：

c = 200

2.结构体(实体类)

type StructA struct {param1 intparam2 stringparam3 boolparam4 StructBparam5 *intparam6 *StructB
}type StructB struct {param1 int
}func test28() {var a StructAa.param1 = 1a.param2 = "a"a.param3 = truevar b StructBb.param1 = 10a.param4 = bc := 20a.param5 = &cvar d StructBd.param1 = 30a.param6 = &dfmt.Printf("param1 value is [%d]\n", a.param1)fmt.Printf("param2 value is [%s]\n", a.param2)fmt.Printf("param3 value is [%t]\n", a.param3)fmt.Printf("param4 value is [%v, %+v, %#v]\n", a.param4, a.param4, a.param4)fmt.Printf("param5 value is [%p, %#p]\n", a.param5, a.param5)fmt.Printf("param1 value is [%d]\n", a.param6.param1)
}

结果：

param1 value is [1]
param2 value is [a]
param3 value is [true]
param4 value is [{10}, {param1:10}, main.StructB{param1:10}]
param5 value is [0xc0000a60d8, c0000a60d8]
param1 value is [30]

3.Map

3.1.Map值的获取

func test33() {m := make(map[string]int)m["key1"] = 1m["key2"] = 2m["key3"] = 3fmt.Printf("key1's value is %d\n", m["key1"])fmt.Printf("m‘s length is %d\n", len(m))key4, status := m["key4"]if status {fmt.Println("key4 value is ", key4)} else {fmt.Println("key4 is not exist.")}
}

结果：

key1's value is 1
m‘s length is 3
key4 is not exist.

说明：
直接获取map的值的时候，返回的第二个参数为：是否存在， bool类型

3.2.Map的遍历

func test33() {m := make(map[string]int)m["key1"] = 1m["key2"] = 2m["key3"] = 3for key, value := range m {fmt.Printf("1--->key is %s, value is %d\n", key, value)}n := map[string]string{"a": "value1", "b": "value2", "c": "value3"}for key, value := range n {fmt.Printf("2--->key is %s, value is %s\n", key, value)}
}

结果：

1--->key1's value is 1
1--->key is key3, value is 3
1--->key is key1, value is 1
1--->key is key2, value is 2
2--->key is c, value is value3
2--->key is a, value is value1
2--->key is b, value is value2

说明：
map 遍历的时候，顺序不是固定的

3.3.删除和清空

func test34() {n := map[string]string{"a": "value1", "b": "value2", "c": "value3"}delete(n, "a")for key, value := range n {fmt.Printf("key is %s, value is %s\n", key, value)}clear(n)fmt.Println("n map: ", n)
}

结果：

key is b, value is value2
key is c, value is value3
n map:  map[]

3.4.判断两个map是否相等

package mainimport ("fmt""maps"
)func test35() {m := map[string]string{"a": "value1", "b": "value2", "c": "value3"}n := map[string]string{"a": "value1", "b": "value2", "c": "value3"}if maps.Equal(m, n) {fmt.Println("m == n")}
}