Go（一）：Go基础语法入门

Love The Way You Lie 2024-03-23 13:01 15阅读 0赞

#### Go基础语法入门 ####

*   *  第一个go程序
     *  变量
     *  常量
     *  数据类型
     *  字符串处理
     *  \`++\` \`--\` 运算符
     *  逻辑运算符
     *  循环 \`for ... := range ...\`
     *  \`switch\`
     *  死循环
     *  数组的CURD
     *  \`map\`的CURD
     *  函数
     *  \`defer\`
     *  \`init\`初始化函数
     *  指针
     *  \`类型定义\` 与 \`类型别名\`
     *  结构体
     *  方法
     *  接口
     *  继承
     *  构造函数

### 第一个go程序 ###

*  `go.mod`
    
        module go-app
        
        go 1.20
 *  `user/user.go`
    
        package user
        
        // Hello 首字母大写为公共方法
        func Hello() string {
              
            return "Hello"
        }
 *  `main.go`
    
        package main
        
        import (
            "fmt"
            "go-app/user"
        )
        
        func main() {
              
            str := user.Hello()
            fmt.Println(str)
        }

### 变量 ###

> 声明的变量必须使用，否则报错异常

package main
    
    import (
    	"fmt"
    )
    
    func funA() (string, int) {
        
    	// 匿名变量
    	return "Lee", 12
    }
    
    func main() {
        
    	// 变量初始化
    	var name string = "123"
    	fmt.Println(name) // 123
    
    	// 批量变量初始化
    	var (
    		realName string = "Lee"
    		age      int    = 24
    		sex      string = "难～"
    	)
    	fmt.Printf("%v ---> %v ---> %v \n", realName, age, sex) // Lee ---> 24 ---> 难～
    
    	// 类型推断
    	var say = "Hello"
    	fmt.Println(say) // Hello
    
    	// 批量初始化
    	var a, b, c = 1, 2, 3
    	fmt.Printf("%v ---> %v ---> %v \n", a, b, c) // 1 ---> 2 ---> 3
    
    	// （短变量声明）只能应用于函数内部
    	x := 4
    	y := 5
    	z := 6
    	fmt.Printf("%v ---> %v ---> %v \n", x, y, z) // 4 ---> 5 ---> 6
    
    	// 匿名变量
    	str, num := funA()
    	fmt.Println(str, num) // Lee 12
    }

### 常量 ###

*  `基本常量`
    
        const HELLO = "Hello Lee!!!"
 *  `iota` 从0开始，每次调用自动加1
    
        const (
            count1 = iota
            count2 = iota
            count3 = iota
        )
        fmt.Println(count1, count2, count3) // 0 1 2
 *  `_` 跳过
    
        const (
            count1 = iota
            _
            count3 = iota
        )
        fmt.Println(count1, count3) // 0 2
 *  `中间插值` 等价于跳过
    
        const (
            count1 = iota
            count2 = 100
            count3 = iota
        )
        fmt.Println(count1, count2, count3) // 0 100 2

### 数据类型 ###

package main
    
    import "fmt"
    
    func i() string {
        
    	return "I"
    }
    
    func main() {
        
    	var a = "Lee"
    	var b = 18
    	var c = true // 注意：不允许用0或1来表示false或true
    	var d = 12.5
    	var e = &d                                                                                                    // 取d的地址（指针类型）
    	var f = [...]int{
        1, 2, 3}                                                                                     // [...] 省略长度
    	var g = []int{
        1, 2, 3}                                                                                        // 动态数组
    	var h = [4]int{
        1, 2, 3}                                                                                       // 固定长度数组
    	var j = `
    		<html>
    			<body>
    				Hello Lee
    			</body>
    		</html>
    		` // 字符串字面量，可换行
    
    	fmt.Printf("%T \n", a)   // string
    	fmt.Printf("%T \n", b)   // int
    	fmt.Printf("%T \n", c)   // bool
    	fmt.Printf("%T \n", d)   // float64
    	fmt.Printf("%T \n", e)   // *float64
    	fmt.Printf("%T \n", f)   // [3]int
    	fmt.Printf("%T \n", g)   // []int
    	fmt.Printf("%T \n", h)   // [4]int
    	fmt.Printf("%T \n", i)   // func() string
    	fmt.Printf("%T \n", nil) // <nil>
    	fmt.Printf("%v \n", j)   // 字符串...
    
    }

### 字符串处理 ###

package main
    
    import (
    	"bytes"
    	"fmt"
    	"strings"
    )
    
    func main() {
        
    
    	// 字符串拼接
    	a := "Hello"
    	b := "Lee"
    	msg1 := fmt.Sprintf("%s %s!!!", a, b)
    	fmt.Println(msg1) // Hello Lee!!!
    
    	msg2 := strings.Join([]string{
        a, b}, "-")
    	fmt.Println(msg2) // Hello-Lee
    
    	var buffer bytes.Buffer
    	buffer.WriteString("Hello ")
    	buffer.WriteString("Lee")
    	fmt.Println(buffer.String()) // Hello Lee
    
    	// 字符串切片
    	msg3 := "Hello Lee, My name is WangDeFa!!!"
    	fmt.Println(msg3[1])   // 101 获取字符串索引为1的原始字节
    	fmt.Println(msg3[2:7]) // llo L
    	fmt.Println(msg3[3:])  // lo Lee, My name is WangDeFa!!!
    	fmt.Println(msg3[:4])  // Hell
    
    	// 字符串分割
    	msg4 := "Hello Lee, My name is WangDeFa!!!"
    	fmt.Println(strings.Split(msg4, "e")) // [H llo L  , My nam  is WangD Fa!!!]
    
    	// 是否包含某个字符串
    	msg5 := "Hello Lee!!!"
    	fmt.Println(strings.Contains(msg5, "ee"))  // true
    	fmt.Println(strings.Contains(msg5, "ele")) // false
    
    	// 转换为大小写
    	msg6 := "Hello Lee!!!"
    	fmt.Println(strings.ToUpper(msg6)) // HELLO LEE!!!
    	fmt.Println(strings.ToLower(msg6)) // hello lee!!!
    
    	// 判断开头或结尾是否有指定字符串
    	msg7 := "Hello Lee!!!"
    	fmt.Println(strings.HasPrefix(msg7, "Hello"))  // true
    	fmt.Println(strings.HasSuffix(msg7, "Lee"))    // false
    	fmt.Println(strings.HasSuffix(msg7, "Lee!!!")) // true
    
    	// 查询字符串索引值
    	msg8 := "Hello Lee!!!"
    	fmt.Println(strings.Index(msg8, "ee")) // 7
    	fmt.Println(strings.Index(msg8, "e"))  // 1
    }

### `++` `--` 运算符 ###

> `++` `--` 是单独的运算符，不能添加到表达式中

package main
    
    import "fmt"
    
    func main() {
        
    	a := 123
    
    	a++
    	fmt.Println(a) // 124
    
    	a--
    	fmt.Println(a) // 123
    }

***`错误形式`***

a := 123
    ++a // Error: '++' unexpected
    --a // Error: '--' unexpected
    123 + a++ // Error: Cannot assign to 123 +

### 逻辑运算符 ###

> `||` `&&` `!` 只能应用于`bool`值之间

### 循环 `for ... := range ...` ###

package main
    
    import "fmt"
    
    func main() {
        
    	list := [...]any{
        "Lee", 25, "☹️"}
    	for i, d := range list {
        
    		fmt.Println(i, d) // 0 Lee   1 25   2 ☹️
    	}
    }

### `switch` ###

> 和其他语言不同，不需要添加`break`

package main
    
    import "fmt"
    
    func main() {
        
    	var num int
    	fmt.Scan(&num)
    	switch num {
        
    	case 1:
    		fmt.Println(num)
    	case 2:
    		fmt.Println(num)
    	case 3:
    		fmt.Println(num)
    	case 4, 5, 6:
    		fmt.Println(num)
    	default:
    		fmt.Println("空")
    	}
    }

***`case`表达式***

package main
    
    import "fmt"
    
    func main() {
        
    	var score int
    	fmt.Scan(&score)
    	switch {
        
    	case score >= 90 && score <= 120:
    		fmt.Println("优秀")
    	case score > 120:
    		fmt.Println("作弊")
    	default:
    		fmt.Println("一般")
    	}
    }

***实现类似其他语言不添加`break`的效果(`fallthrough`)***

package main
    
    import "fmt"
    
    func main() {
        
    	var num int
    	fmt.Scan(&num) // 1 --> 一 二 三   2 --> 二 三
    	switch num {
        
    	case 1:
    		fmt.Println("一")
    		fallthrough
    	case 2:
    		fmt.Println("二")
    		fallthrough
    	case 3:
    		fmt.Println("三")
    	case 4, 5, 6:
    		fmt.Println("四五六")
    	default:
    		fmt.Println("空")
    	}
    }

### 死循环 ###

package main
    
    import "fmt"
    
    func main() {
        
    	count := 0
    	for {
        
    		count++
    		fmt.Println(count) // ...
    	}
    }

***跳出循环***

package main
    
    import "fmt"
    
    func main() {
        
    	count := 0
    	for {
        
    		count++
    		fmt.Println(count) // 1 - 100
    		if count > 99 {
        
    			break
    		}
    	}
    }

package main
    
    import "fmt"
    
    func main() {
        
    	count := 0
    	for {
        
    		count++
    		fmt.Println(count) // 1 - 11
    		if count > 10 {
        
    			goto endPrint
    		}
    	}
    
    endPrint: // 标签
    	fmt.Println("结束")
    }

### 数组的CURD ###

package main
    
    import "fmt"
    
    func main() {
        
    	list := []any{
        1, true, "Lee"}
    
    	// 增
    	res1 := append(list, "啥？")
    	fmt.Println(list) // [1 true Lee]
    	fmt.Println(res1) // [1 true Lee 啥？]
    	res2 := append(list, res1...)
    	fmt.Println(list) // [1 true Lee]
    	fmt.Println(res2) // [1 true Lee 1 true Lee 啥？]
    
    	// 改
    	list[1] = "假"
    	fmt.Println(list) // [1 假 Lee]
    
    	// 查
    	fmt.Println(list[2])  // Lee
    	fmt.Println(list[1:]) // [假 Lee]
    
    	// 浅拷贝
    	res3 := list
    	res3[0] = 123
    	fmt.Println(list) // [123 假 Lee]
    	fmt.Println(res3) // [123 假 Lee]
    
    	// 深克隆
    	res4 := make([]any, len(list))
    	copy(res4, list)
    	res4[1] = 456
    	fmt.Println(list) // [123 假 Lee]
    	fmt.Println(res4) // [123 456 Lee]
    
    	// 删 - 删除索引1
    	list = append(list[:1], list[2])
    	fmt.Println(list) // [123 Lee]
    }

### `map`的CURD ###

***CURD***

package main
    
    import "fmt"
    
    func main() {
        
    	//data := make(map[string]any)
    	//data["name"] = "Lee"
    	data := map[string]any{
        
    		"name": "Lee",
    	}
    	// 改
    	data["name"] = "Tom"
    	// 增
    	data["age"] = 18
    	data["height"] = 171
    	// 删
    	delete(data, "height")
    	// 查
    	fmt.Printf("%v ---> %v ---> %v", data["name"], data["age"], data["height"]) // Tom ---> 18 ---> <nil>
    }

***拷贝***

package main
    
    import "fmt"
    
    func main() {
        
    	data1 := map[string]any{
        
    		"name":   "Lee",
    		"age":    18,
    		"height": 171,
    	}
    
    	// 浅拷贝
    	data2 := data1
    	data2["name"] = "Tom"
    	fmt.Printf("%v ---> %v ---> %v\n", data1["name"], data1["age"], data1["height"]) // Tom ---> 18 ---> 171
    	fmt.Printf("%v ---> %v ---> %v\n", data2["name"], data2["age"], data2["height"]) // Tom ---> 18 ---> 171
    
    	// 深克隆
    	data3 := make(map[string]any)
    	for key, value := range data1 {
        
    		data3[key] = value
    	}
    	data3["name"] = "Lucy"
    	fmt.Printf("%v ---> %v ---> %v\n", data1["name"], data1["age"], data1["height"]) // Tom ---> 18 ---> 171
    	fmt.Printf("%v ---> %v ---> %v\n", data3["name"], data3["age"], data3["height"]) // Lucy ---> 18 ---> 171
    
    }

***判断字段是否存在***

package main
    
    import "fmt"
    
    func main() {
        
    	data := map[string]any{
        
    		"name":   "Lee",
    		"age":    18,
    		"height": 171,
    	}
    
    	height, hasHeight := data["height"]
    	fmt.Println(height, hasHeight) // 171 true
    
    	like, hasLike := data["like"]
    	fmt.Println(like, hasLike) // <nil> false
    }

### 函数 ###

***基本函数***

package main
    
    import "fmt"
    
    func sum1(a int, b int) (res int) {
        
    	res = a + b
    	return res
    }
    
    func sum2(a int, b int) int {
        
    	res := a + b
    	return res
    }
    
    func sum3(a int, b int) (int, int, int) {
        
    	res := a + b
    	return a, b, res
    }
    
    func sum4(a int, b int, c ...int) int {
        
    	res := a + b
    	for _, v := range c {
        
    		res += v
    	}
    	return res
    }
    
    func main() {
        
    	fmt.Println(sum1(1, 1)) // 2
    
    	fmt.Println(sum2(1, 1)) // 2
    
    	fmt.Println(sum3(1, 1)) // 1 1 2
    
    	a, b, c := sum3(1, 1)
    	fmt.Println(a, b, c) // 1 1 2
    
    	fmt.Println(sum4(1, 2, 3, 4, 5)) // 15
    }

***函数类型***

package main
    
    import "fmt"
    
    type demo func(int, int) int
    
    func sum(a int, b int) int {
        
    	return a + b
    }
    
    func max(a int, b int) int {
        
    	if a > b {
        
    		return a
    	} else {
        
    		return b
    	}
    }
    
    func main() {
        
    	var d demo
    
    	d = sum
    	s := d(1, 2)
    	fmt.Println(s) // 3
    
    	d = max
    	m := d(1, 2)
    	fmt.Println(m) // 2
    }

***回调函数***

package main
    
    import "fmt"
    
    func sayHello(name string, callback func(string)) {
        
    	fmt.Printf("%v: Hello!\n", name)
    	name = "Tom"
    	if callback != nil {
        
    		callback(name)
    	}
    }
    
    func sayHi(name string) {
        
    	fmt.Printf("%v: Hi!\n", name)
    }
    
    func main() {
        
    	sayHello("Lee", sayHi) // Lee: Hello!   Tom: Hi!
    }

***匿名函数***

package main
    
    import "fmt"
    
    func sayHello(name string, callback func(string)) {
        
    	fmt.Printf("%v: Hello!\n", name)
    	name = "Tom"
    	if callback != nil {
        
    		callback(name)
    	}
    }
    
    func main() {
        
    	sayHello("Lee", func(name string) {
        
    		fmt.Printf("%v: Hi!\n", name)
    	}) // Lee: Hello!   Tom: Hi!
    }

***立即执行函数***

package main
    
    import "fmt"
    
    func main() {
        
    	name := func(name string) string {
        
    		return name
    	}("Lee")
    
    	fmt.Println(name) // Lee
    }

***闭包***

package main
    
    import "fmt"
    
    func say() func(string) string {
        
    	msg := "Hi, "
    	return func(s string) string {
        
    		msg += s
    		return msg
    	}
    }
    
    func main() {
        
    	str := say()
    	fmt.Println(str("Lee"))   // Hi, Lee
    	fmt.Println(str("-Tom.")) // Hi, Lee-Tom.
    }

***递归***

package main
    
    import "fmt"
    
    func fun(n int) int {
        
    	if n == 0 {
        
    		return 1
    	}
    	return n * fun(n-1)
    }
    
    func main() {
        
    	fmt.Println(fun(3)) // 6
    }

### `defer` ###

> 先定义的后输出

package main
    
    import "fmt"
    
    func main() {
        
    	fmt.Println(1)
    	fmt.Println(2)
    	fmt.Println(3)
    	defer fmt.Println(4)
    	defer fmt.Println(5)
    	defer fmt.Println(6)
    	defer fmt.Println(7)
    	fmt.Println(8)
    	fmt.Println(9)
    	fmt.Println(0)
    
    	// 结果：123 890 7654
    }

### `init`初始化函数 ###

> 执行顺序 `变量函数 ---> init函数(按从上到下) ---> main函数`

package main
    
    import "fmt"
    
    func init() {
        
    	fmt.Println("init1")
    }
    
    var data = func() any {
        
    	fmt.Println("num")
    	return nil
    }()
    
    func init() {
        
    	fmt.Println("init2")
    }
    
    func main() {
        
    	fmt.Println("main")
    }
    
    func init() {
        
    	fmt.Println("init3")
    }
    
    // 结果： num init1 init2 init3 main

### 指针 ###

package main
    
    import "fmt"
    
    func main() {
        
    	var a = 123
    	var b *int // int类型的指针变量
    
    	// 打印变量值
    	fmt.Println(b) // <nil>
    
    	// 打印变量地址
    	fmt.Println(&a) // 0xc0000ac008
    	fmt.Println(&b) // 0xc0000a6018
    
    	b = &a
    	// 打印变量地址
    	fmt.Println(b) // 0xc0000ac008
    	// 打印变量值
    	fmt.Println(*b) // 123
    }

***指向数组的指针***

package main
    
    import "fmt"
    
    func main() {
        
    	var a = []int{
        1, 2, 3}
    	var b [3]*int
    
    	// 打印变量值
    	fmt.Println(b) // [<nil> <nil> <nil>]
    
    	// 打印变量地址
    	fmt.Println(&a)                  // &[1 2 3]
    	fmt.Println(&a[0], &a[1], &a[2]) // 0xc00001e0d8 0xc00001e0e0 0xc00001e0e8
    	fmt.Println(&b)                  // &[<nil> <nil> <nil>]
    	fmt.Println(&b[0], &b[1], &b[2]) // 0xc000010048 0xc000010050 0xc000010058
    
    	for i := range a {
        
    		b[i] = &a[i]
    		fmt.Println(b[i])  // 0xc00001e0d8 0xc00001e0e0 0xc00001e0e8
    		fmt.Println(*b[i]) // 1 2 3
    	}
    }

### `类型定义` 与 `类型别名` ###

package main
    
    import "fmt"
    
    // NewInt 自定义类型
    type NewInt int
    
    // NewBool 类型别名
    type NewBool = bool
    
    func main() {
        
    	var a NewInt
    	fmt.Println(a) // 0
    	var b NewBool
    	fmt.Println(b) // false
    }

### 结构体 ###

package main
    
    import "fmt"
    
    type UserInfo struct {
        
    	name   string
    	age    int
    	height float64
    }
    
    func main() {
        
    	var info UserInfo
    	info.name = "Lee"
    	info.age = 18
    	info.height = 171
    	fmt.Println(info) // {Lee 18 171}
    }

***匿名结构体***

package main
    
    import "fmt"
    
    func main() {
        
    	var info struct {
        
    		name   string
    		age    int
    		height float64
    	}
    	info.name = "Lee"
    	info.age = 18
    	info.height = 171
    	fmt.Println(info) // {Lee 18 171}
    }

***结构体赋值***

package main
    
    import "fmt"
    
    type UserInfo struct {
        
    	name        string
    	age, height int
    }
    
    func main() {
        
    	
    	var info UserInfo
    
    	// 方式1
    	info.name = "Lee"
    	info.age = 18
    	info.height = 171
    
    	// 方式2
    	info = UserInfo{
        
    		"Lee", 18, 171,
    	}
    
    	// 方式3
    	info = UserInfo{
        
    		name:   "Lee",
    		height: 171,
    	}
    
    	fmt.Println(info) // {Lee 18 171}
    }

***结构体的指针***

package main
    
    import "fmt"
    
    type UserInfo struct {
        
    	name        string
    	age, height int
    }
    
    func main() {
        
    	var lee *UserInfo
    
    	fmt.Println(lee)  // <nil>
    	fmt.Println(&lee) // 0xc000012028
    
    	var tom = UserInfo{
        
    		name:   "Lee",
    		age:    18,
    		height: 171,
    	}
    
    	lee = &tom
    	fmt.Println(lee)  // &{Lee 18 171}
    	fmt.Println(&lee) // 0xc000012028
    	fmt.Println(*lee) // {Lee 18 171}
    }

package main
    
    import "fmt"
    
    type UserInfo struct {
        
    	name        string
    	age, height int
    }
    
    func main() {
        
    	// 初始化结构体的指针
    	var lee = new(UserInfo)
    
    	fmt.Println(lee)  // &{ 0 0}
    	fmt.Println(&lee) // 0xc000012028
    
    	var tom = UserInfo{
        
    		name:   "Lee",
    		age:    18,
    		height: 171,
    	}
    
    	lee = &tom
    	fmt.Println(lee)  // &{Lee 18 171}
    	fmt.Println(&lee) // 0xc000012028
    	fmt.Println(*lee) // {Lee 18 171}
    }

***结构体的嵌套***

package main
    
    import "fmt"
    
    type UserInfo struct {
        
    	name        string
    	age, height int
    }
    
    type Person struct {
        
    	userInfo UserInfo
    	msg      string
    }
    
    func main() {
        
    	var tom = Person{
        
    		userInfo: UserInfo{
        
    			name:   "Lee",
    			age:    18,
    			height: 171,
    		},
    		msg: "Hi",
    	}
    	fmt.Println(tom) // {
        {Lee 18 171} Hi}
    }

***结构体作为参数***

package main
    
    import "fmt"
    
    type UserInfo struct {
        
      name        string
      age, height int
    }
    
    type Person struct {
        
      userInfo UserInfo
      msg      string
    }
    
    func say1(person Person) {
        
      person.msg = "Hello"
      person.userInfo.name = "Tom"
      fmt.Println(person.msg, person.userInfo.name)
    }
    
    func say2(person *Person) {
        
      person.msg = "Hello"
      person.userInfo.name = "Tom"
      fmt.Println(person.msg, person.userInfo.name)
    }
    
    func main() {
        
      var person1 = Person{
        
        userInfo: UserInfo{
        
          name:   "Lee",
          age:    18,
          height: 171,
        },
        msg: "Hi",
      }
      say1(person1)                      // Hello Tom
      fmt.Println(person1.msg)           // Hi
      fmt.Println(person1.userInfo.name) // Lee
    
      var person2 = Person{
        
        userInfo: UserInfo{
        
          name:   "Lee",
          age:    18,
          height: 171,
        },
        msg: "Hi",
      }
      say2(&person2)                     // Hello Tom
      fmt.Println(person2.msg)           // Hello
      fmt.Println(person2.userInfo.name) // Tom
    }

### 方法 ###

> 方法的接收者是结构体，包含值类型和引用类型时，那么值类型被复制，引用类型不被复制而是引用

package main
    
    import "fmt"
    
    type UserInfo struct {
        
      name        string
      age, height int
      likes       []string
    }
    
    // info为接收者用于接收
    func (info UserInfo) say() {
        
      info.age = 20
      info.likes[2] = "play"
      fmt.Println(info)
    }
    
    func main() {
        
      var userInfo = UserInfo{
        
        name:   "Lee",
        age:    18,
        height: 171,
        likes:  []string{
        "吃", "喝", "玩", "乐"},
      }
      userInfo.say()        // {Lee 20 171 [吃 喝 play 乐]} 注意值类型和引用类型的区别
      fmt.Println(userInfo) // {Lee 18 171 [吃 喝 play 乐]} 注意值类型和引用类型的区别
    }

> 方法的接收者是指针类型结构体时，那么不被复制而是引用

package main
    
    import "fmt"
    
    type UserInfo struct {
        
    	name        string
    	age, height int
    	likes       []string
    }
    
    // info为接收者用于接收
    func (info *UserInfo) say() {
        
    	info.age = 20
    	info.likes[2] = "play"
    	fmt.Println(*info)
    }
    
    func main() {
        
    	var userInfo = UserInfo{
        
    		name:   "Lee",
    		age:    18,
    		height: 171,
    		likes:  []string{
        "吃", "喝", "玩", "乐"},
    	}
    	userInfo.say()        // {Lee 20 171 [吃 喝 play 乐]} 注意值类型和引用类型的区别
    	fmt.Println(userInfo) // {Lee 20 171 [吃 喝 play 乐]} 注意值类型和引用类型的区别
    }

### 接口 ###

> 接口内的方法必须定义，否则报错

package main
    
    import "fmt"
    
    // Sayer 说接口
    type Sayer interface {
        
    	say(msg string)
    }
    
    // Mover 移动接口
    type Mover interface {
        
    	move(start int, end int) (name string, distance int)
    }
    
    // Animaler 动物接口
    type Animaler interface {
        
    	Sayer
    	Mover
    }
    
    // Lee 结构体，存放姓名
    type Lee struct {
        
    	name string
    }
    
    func (lee Lee) say(msg string) {
        
    	fmt.Println(msg + lee.name)
    }
    
    func (lee Lee) move(start int, end int) (name string, distance int) {
        
    	distance = end - start
    	return lee.name, distance
    }
    
    func main() {
        
        var lee Animaler
        lee = Lee{
        name: "Lee"}
    	lee.say("Hi,")
    	name, distance := lee.move(0, 10)
    	fmt.Println(name, distance)
    }

***`OCP`: “开-闭”原则***

package main
    
    import "fmt"
    
    type Animaler interface {
        
    	eat()
    	sleep()
    }
    
    type Person struct {
        
    	name string
    }
    
    func (person Person) eat() {
        
    	fmt.Println(person.name + ",吃...")
    }
    
    func (person Person) sleep() {
        
    	fmt.Println(person.name + ",睡...")
    }
    
    func funA(animal Animaler) {
        
    	animal.eat()
    	animal.sleep()
    }
    
    func (person Person) funB(animal Animaler) {
        
    	animal.eat()
    	animal.sleep()
    }
    
    func main() {
        
    	var animal Animaler = Person{
        name: "Dog"}
    	animal.eat()   // Dog,吃...
    	animal.sleep() // Dog,睡...
    	funA(animal)   // Dog,吃...  Dog,睡...
    
    	var lee Animaler = Person{
        name: "Lee"}
    	var tom Animaler = Person{
        name: "Tom"}
    	person := Person{
        }
    	person.funB(lee) // Lee,吃...  Lee,睡...
    	person.funB(tom) // Tom,吃...  Tom,睡...
    }

### 继承 ###

> 结构体嵌套来实现继承

***继承自`User`的`UserInfo`结构体***

package main
    
    import "fmt"
    
    // User 父结构体
    type User struct {
        
      say   func(msg string)
      sleep func()
    }
    
    // UserInfo 子结构体
    type UserInfo struct {
        
      name   string
      age    int
      height float64
      User
    }
    
    func main() {
        
      lee := UserInfo{
        
        name:   "Lee",
        age:    18,
        height: 171.123,
        User: User{
        
          say: func(msg string) {
        
            fmt.Println(msg)
          },
          sleep: func() {
        
            fmt.Println("sleep...")
          },
        },
      }
    
      fmt.Println(lee) // {Lee 18 171.123 {0x102f8f610 0x102f8f690}}
    
      lee.say("Hi," + lee.name)      // Hi,Lee
      lee.User.say("Hi," + lee.name) // Hi,Lee
    
      lee.User.sleep() // sleep...
      lee.sleep()      // sleep...
    }

### 构造函数 ###

package main
    
    import "fmt"
    
    type UserInfo struct {
        
    	name   string
    	age    int
    	height float64
    }
    
    // initUserInfo 构造函数
    func initUserInfo(name string, age int, height float64) *UserInfo {
        
    	return &UserInfo{
        name: name, age: age, height: height}
    }
    
    func main() {
        
    
    	info := UserInfo{
        
    		name:   "Lee",
    		age:    18,
    		height: 171.123,
    	}
    
    	person := initUserInfo(info.name, info.age, info.height)
    	fmt.Println(info)   // {Lee 18 171.123}
    	fmt.Println(person) // &{Lee 18 171.123}
    
    	person.name = "Tom"
    	fmt.Println(info)   // {Lee 18 171.123}
    	fmt.Println(person) // &{Tom 18 171.123}
    }