Golang 教程1
注意，该文档只适合有编程基础的同学，这里的go教程只给出有区别的知识点
go教程\]('[Go基础 · Go语言中文文档 (topgoer.com)](https://www.topgoer.com/go%E5%9F%BA%E7%A1%80/)') ### 一、基础 tip: **下划线_ 可以起到忽略的作用** 运行以下命令来初始化一个新的 Go 模块： ```go // 如你的项目在 gocode/testproject01/unit2/demo01 中 （从src后开始， 用'/'隔开）。 go mod init gocode/testproject01/unit2/demo01 //1、go mod init：这是 Go 的模块初始化命令，用于创建一个新的 go.mod 文件，它是 Go 模块的元数据文件，用于记录模块的基本信息和依赖关系。 //2、gocode/testproject01/unit2/demo01：这是你指定的模块名称。这个名称将成为你的模块在 Go 生态系统中的唯一标识符。 //输入操作 _, err := fmt.Scanf("%v", &name) //录入数据的时候，类型一定要匹配。 // _：这是一个空白标识符，在 Go 语言中用来忽略赋给它的值。 //1、 fmt.Scanln 函数返回两个值：第一个是扫描的元素数量，第二个是错误（如果有）。因为我们只关心错误（第二个返回值），所以我们使用 _ 来忽略第一个返回值。 //2、 err：这是用来存储 fmt.Scanln 函数返回的错误值。如果函数执行成功，则 err 将为 nil；如果发生错误，则 err 将包含具体的错误信息。 //3、 :=：这是一个短声明语法，用于声明并初始化一个变量。在这里，我们声明了一个名为 err 的变量，并将其初始化为 fmt.Scanln(&a) 函数的第二个返回值。 //4、 fmt.Scanln(&a)：这是 fmt.Scanln 函数调用，它从标准输入读取数据，并尝试将读取的数据转换成变量 a 的类型（这里是整型 int）。它需要一个变量的引用作为参数，这里使用了 &a。 ``` #### 1、 自动缩进 ```go gofmt -w xxx.go ``` ##### 2、 **关于赋值, 支持这种声明** ```go sex := "man" var n4, name, n5 = 10, "jack", 7.8 n6, height := 6.9, 100.6 ``` ##### 3、**全局赋值， 省时省力** ```go var ( n9 = 100 n10 = "dasda" ) //导入包也可以如此操作, 如 import ( "fmt" "strconv" ) ``` ##### 4、**字符串一旦定义好，值不可变** ```go name = "黎明" name[0] = "牛" //会报错 ``` ##### 5、 **如果字符串需要赋值特殊的字符（关键字、\<、= ...），用反单引号包裹** ```go str := ` var a string = 1 string a < 1231 ` ``` ##### 6、**类型转换 T() 显示转化, T为你想要转换的类型** ```````````````````````````````````````````````````````````````````````````````````````````````````go a := 100 b := float32(a) fmt.Println(a, b) //注意，类型大的转化至类型小的变量，高位部分会被截断 var n1 int64 = 888888888 var n2 = int8(n1) fmt.Println(n2) fmt.Printf("%T", n2c) `````````````````````````````````````````````````````````````````````````````````````````````````` (base) PS E:\Goproject\src\gocode\testproject01\unit2\demo01> go run .\main.go 56 int8 `````````````````````````````````````````````````````````````````````````````````````````````````` var n3 int32 = 12 //会报错， var n4 int64 = int64(n3) + 30 var n4 int8 = n3 + 30 fmt.Println(n3) fmt.Println(n4) `````````````````````````````````````````````````````````````````````````````````````````````````` (base) PS E:\Goproject\src\gocode\testproject01\unit2\demo01> go run .\main.go # command-line-arguments .\main.go:5:16: cannot use n3 + 30 (value of type int32) as int8 value in variable declaration `````````````````````````````````````````````````````````````````````````````````````````````````` ``````````````````````````````````````````````````````````````````````````````````````````````````` ##### 7、 **string类型转化，strconv.parseInt等函数返回的是2个值（value， err）所以应有2个变量承接** ```````````````````````````````````````````````````````````````````````````````````````````````````go func main() { str := "123" i, err := strconv.Atoi(str) if err != nil { fmt.Println(err) } else { fmt.Println(i) } } `````````````````````````````````````````````````````````````````````````````````````````````````` (base) PS E:\Goproject\src\gocode\testproject01\unit2\demo01> go run .\main.go 123 `````````````````````````````````````````````````````````````````````````````````````````````````` ``````````````````````````````````````````````````````````````````````````````````````````````````` ##### 8、 **指针** ```````````````````````````````````````````````````````````````````````````````````````````````````go func main() { var a int = 10 var ptr *int = &a fmt.Println("Value of a is ", a) fmt.Println("Value of a is ", *ptr) fmt.Println("Address of a is ", ptr) fmt.Println("Address of a is ", &a) fmt.Println("Address of a is ", &ptr) *ptr = 20 fmt.Println("Value of a is ", a) } `````````````````````````````````````````````````````````````````````````````````````````````````` (base) PS E:\Goproject\src\gocode\testproject01\unit2\demo01> go run .\main.go Value of a is 10 Value of a is 10 Address of a is 0xc00000a0f8 Address of a is 0xc00000a0f8 Address of a is 0xc000078050 Value of a is 20 ````````````````````````````````````````````````````````````````````````````````````````````````` ``````````````````````````````````````````````````````````````````````````````````````````````````` ##### 9、**分支控制** ```go //单、多分支， 注意：条件表达式可以不写，也建议不写 if 条件表达式 { 逻辑代码 } else if 条件表达式 { 逻辑代码 } else { 逻辑代码 } // switch 不用额外加break 防止代码穿透 switch 条件表达式 { case 条件满足1： xxx case 条件满足2： xxx 。。。 default: XXX } // 如： func main() { var a int fmt.Println("请输入数字：") _, err := fmt.Scanln(&a) if err != nil { fmt.Println("输入错误:", err) return } if a == 1 { fmt.Println("a = 1") } else if a == 2 { fmt.Println("a = 2") } else { fmt.Println("a = 3") } } //可以使用 fallthrough 穿透，但只能穿透一层 ``` ##### 10、 **循环** （go里面没有while循环） ```````````````````````````````````````````````````````````````````````````````````````````````````go //跟c语言一样，条件表达式不用（）包裹 func main() { i, sum := 0, 0 for i = 0; i < 10; i++ { sum += i } fmt.Println(sum) } `````````````````````````````````````````````````````````````````````````````````````````````````` (base) PS E:\Goproject\src\gocode\testproject01\unit2\demo01> go run .\main.go 45 `````````````````````````````````````````````````````````````````````````````````````````````````` //可以跟while一样, 格式灵活 func main() { for { fmt.Println("hello Golang") } } `````````````````````````````````````````````````````````````````````````````````````````````````` (base) PS E:\Goproject\src\gocode\testproject01\unit2\demo01> go run .\main.go hello Golang hello Golang hello Golang hello Golang hello Golang 。。。 `````````````````````````````````````````````````````````````````````````````````````````````````` ``````````````````````````````````````````````````````````````````````````````````````````````````` ###### 10.1 **for range （Go 特有，可以遍历数组、切片、字符串、map以及通道，形式上有点类似于foreach）** ```go func main() { str := "hello world" for i := 0; i < len(str); i++ { fmt.Printf("%c", str[i]) } } //等效于 // 这里的 fmt.Printf("索引为 %d, 对应的值为 %c \n", i, val) 是带格式的输出， 可以类比 fmt.Println() func main() { str := "hello world" for i, val := range str { fmt.Printf("索引为 %d, 对应的值为 %c \n", i, val) } } ```