diff --git a/README.md b/README.md index 94da484..401f326 100644 --- a/README.md +++ b/README.md @@ -18,6 +18,7 @@ Quick Reference [C](./docs/c.md) [Docker](./docs/docker.md) [Dockerfile](./docs/dockerfile.md) +[Golang](./docs/golang.md) [JSON](./docs/json.md) [Markdown](./docs/markdown.md) [TOML](./docs/toml.md) diff --git a/docs/golang.md b/docs/golang.md new file mode 100644 index 0000000..024e85f --- /dev/null +++ b/docs/golang.md @@ -0,0 +1,966 @@ +Golang 备忘清单 +=== + +该备忘单提供了帮助您使用 [Golang](https://golang.org) 的基本语法和方法。 + +入门 +-------- + +### hello.go + +```go +package main +import "fmt" +func main() { + fmt.Println("Hello, world!") +} +``` + +直接运行 + +```shell +$ go run hello.go +Hello, world! +``` + +或者在 [Go repl](https://repl.it/languages/go) 中尝试一下 + +### 变量 + +```go +var s1 string +s1 = "Learn Go!" +// 一次声明多个变量 +var b, c int = 1, 2 +var d = true +``` + +简短声明 + +```go +s1 := "Learn Go!" // string +b, c := 1, 2 // int +d := true // bool +``` + +参见：[基本类型](#golang-基本类型) + +### 函数 + +```go +package main +import "fmt" +// 程序的入口点 +func main() { + fmt.Println("Hello world!") + say("Hello Go!") +} +func say(message string) { + fmt.Println("You said: ", message) +} +``` + +参见：[函数(Functions)](#golang-函数) + +### 注释 + +```go +// 单行注释 +/* 这是 +多行注释 */ +``` + +### 如果语句 + +```go +if true { + fmt.Println("Yes!") +} +``` + +参见：[条件控制](#golang-条件控制) + +Golang 基本类型 +-------- + +### 字符串 Strings + +```go +s1 := "Hello" + "World" +s2 := `A "raw" string literal +can include line breaks.` +// 输出：11 +fmt.Println(len(s1)) +// 输出：Hello +fmt.Println(string(s1[0:5])) +``` + +字符串的类型为 `字符串` + +### 数字 Numbers + +```go +num := 3 // int +num := 3. // float64 +num := 3 + 4i // complex128 +num := byte('a') // byte (alias: uint8) +var u uint = 7 // uint (unsigned) +var p float32 = 22.7 // 32-bit float +``` + +#### 操作符 Operators + +```go +x := 5 +x++ +fmt.Println("x + 4 =", x + 4) +fmt.Println("x * 4 =", x * 4) +``` + +参见：[更多操作符](#运算符和标点符号) + +### 布尔值 Booleans + +```go +isTrue := true +isFalse := false +``` + +#### 操作符 + +```go +fmt.Println(true && true) // true +fmt.Println(true && false) // false +fmt.Println(true || true) // true +fmt.Println(true || false) // true +fmt.Println(!true) // false +``` + +参见：[更多操作符](#运算符和标点符号) + +### 数组 Arrays + + +```go +┌────┬────┬────┬────┬─────┬─────┐ +| 2 | 3 | 5 | 7 | 11 | 13 | +└────┴────┴────┴────┴─────┴─────┘ + 0 1 2 3 4 5 +``` + +--- + +```go +primes := [...]int{2, 3, 5, 7, 11, 13} +fmt.Println(len(primes)) // => 6 +// 输出：[2 3 5 7 11 13] +fmt.Println(primes) +// 与 [:3] 相同，输出：[2 3 5] +fmt.Println(primes[0:3]) +``` + +--- + +```go +var a [2]string +a[0] = "Hello" +a[1] = "World" +fmt.Println(a[0], a[1]) //=> Hello World +fmt.Println(a) // => [Hello World] +``` + +#### 2d array + +```go +var twoDimension [2][3]int +for i := 0; i < 2; i++ { + for j := 0; j < 3; j++ { + twoDimension[i][j] = i + j + } +} +// => 2d: [[0 1 2] [1 2 3]] +fmt.Println("2d: ", twoDimension) +``` + +### 指针(Pointers) + +```go +func main () { + b := *getPointer() + fmt.Println("Value is", b) +} + +func getPointer () (myPointer *int) { + a := 234 + return &a +} + +a := new(int) +*a = 234 +``` + +参见：[指针(Pointers)](https://tour.golang.org/moretypes/1) + +### 切片(Slices) + +```go +s := make([]string, 3) +s[0] = "a" +s[1] = "b" +s = append(s, "d") +s = append(s, "e", "f") +fmt.Println(s) +fmt.Println(s[1]) +fmt.Println(len(s)) +fmt.Println(s[1:3]) +slice := []int{2, 3, 4} +``` + +另见：[切片示例](https://gobyexample.com/slices) + +### 常量(Constants) + +```go +const s string = "constant" +const Phi = 1.618 +const n = 500000000 +const d = 3e20 / n +fmt.Println(d) +``` + +### 类型转换 + +```go +i := 90 +f := float64(i) +u := uint(i) +// 将等于字符Z +s := string(i) +``` + +#### 如何获取int字符串？ + +```go +i := 90 +// 需要导入“strconv” +s := strconv.Itoa(i) +fmt.Println(s) // Outputs: 90 +``` + + +Golang 字符串 +-------- + +### 字符串函数 + +```go +package main +import ( + "fmt" + s "strings" +) +func main() { + /* 需要将字符串导入为 s */ + fmt.Println(s.Contains("test", "e")) + /* 内置 */ + fmt.Println(len("hello")) // => 5 + // 输出: 101 + fmt.Println("hello"[1]) + // 输出: e + fmt.Println(string("hello"[1])) +} +``` + +### fmt.Printf + + +```go +package main +import ( + "fmt" + "os" +) +type point struct { + x, y int +} +func main() { + p := point{1, 2} + fmt.Printf("%v\n", p) // => {1 2} + fmt.Printf("%+v\n", p) // => {x:1 y:2} + fmt.Printf("%#v\n", p) // => main.point{x:1, y:2} + fmt.Printf("%T\n", p) // => main.point + fmt.Printf("%t\n", true) // => TRUE + fmt.Printf("%d\n", 123) // => 123 + fmt.Printf("%b\n", 14) // => 1110 + fmt.Printf("%c\n", 33) // => ! + fmt.Printf("%x\n", 456) // => 1c8 + fmt.Printf("%f\n", 78.9) // => 78.9 + fmt.Printf("%e\n", 123400000.0) // => 1.23E+08 + fmt.Printf("%E\n", 123400000.0) // => 1.23E+08 + fmt.Printf("%s\n", "\"string\"") // => "string" + fmt.Printf("%q\n", "\"string\"") // => "\"string\"" + fmt.Printf("%x\n", "hex this") // => 6.86578E+15 + fmt.Printf("%p\n", &p) // => 0xc00002c040 + fmt.Printf("|%6d|%6d|\n", 12, 345) // => | 12| 345| + fmt.Printf("|%6.2f|%6.2f|\n", 1.2, 3.45) // => | 1.20| 3.45| + fmt.Printf("|%-6.2f|%-6.2f|\n", 1.2, 3.45) // => |1.20 |3.45 | + fmt.Printf("|%6s|%6s|\n", "foo", "b") // => | foo| b| + fmt.Printf("|%-6s|%-6s|\n", "foo", "b") // => |foo |b | + s := fmt.Sprintf("a %s", "string") + fmt.Println(s) + fmt.Fprintf(os.Stderr, "an %s\n", "error") +} +``` + +另见：[fmt](https://golang.org/pkg/fmt/) + +### 函数实例 + +| 实例 | Result | +|-------------------------------|-------------| +| Contains("test", "es") | true | +| Count("test", "t") | 2 | +| HasPrefix("test", "te") | true | +| HasSuffix("test", "st") | true | +| Index("test", "e") | 1 | +| Join([]string{"a", "b"}, "-") | a-b | +| Repeat("a", 5) | aaaaa | +| Replace("foo", "o", "0", -1) | f00 | +| Replace("foo", "o", "0", 1) | f0o | +| Split("a-b-c-d-e", "-") | [a b c d e] | +| ToLower("TEST") | test | +| ToUpper("test") | TEST | + +Golang 条件控制 +-------- + +### 有条件的 + +```go +a := 10 +if a > 20 { + fmt.Println(">") +} else if a < 20 { + fmt.Println("<") +} else { + fmt.Println("=") +} +``` + +### if 中的语句 + +```go +x := "hello go!" +if count := len(x); count > 0 { + fmt.Println("Yes") +} +``` + +--- + +```go +if _, err := doThing(); err != nil { + fmt.Println("Uh oh") +} +``` + +### Switch + +```go +x := 42.0 +switch x { + case 0: + case 1, 2: + fmt.Println("Multiple matches") + case 42: // Don't "fall through". + fmt.Println("reached") + case 43: + fmt.Println("Unreached") + default: + fmt.Println("Optional") +} +``` + +参见：[Switch](https://github.com/golang/go/wiki/Switch) + +### For loop + +```go +for i := 0; i <= 10; i++ { + fmt.Println("i: ", i) +} +``` + +### 对于 Range 循环 + +```go +nums := []int{2, 3, 4} +sum := 0 +for _, num := range nums { + sum += num +} +fmt.Println("sum:", sum) +``` + +### While 循环 + +```go +i := 1 +for i <= 3 { + fmt.Println(i) + i++ +} +``` + +### Continue 关键字 + +```go +for i := 0; i <= 5; i++ { + if i % 2 == 0 { + continue + } + fmt.Println(i) +} +``` + +### Break 关键字 + +```go +for { + fmt.Println("loop") + break +} +``` + +Golang 结构和映射 +-------- + +### 定义 + + +```go +package main +import ( + "fmt" +) +type Vertex struct { + X int + Y int +} +func main() { + v := Vertex{1, 2} + v.X = 4 + fmt.Println(v.X, v.Y) // => 4 2 +} +``` + +参见：[结构(Structs)](https://tour.golang.org/moretypes/2) + +### 字面量 + +```go +v := Vertex{X: 1, Y: 2} +// Field names can be omitted +v := Vertex{1, 2} +// Y is implicit +v := Vertex{X: 1} +``` + +您还可以输入字段名 + +### 映射 + + +```go +m := make(map[string]int) +m["k1"] = 7 +m["k2"] = 13 +fmt.Println(m) // => map[k1:7 k2:13] +v1 := m["k1"] +fmt.Println(v1) // => 7 +fmt.Println(len(m)) // => 2 +delete(m, "k2") +fmt.Println(m) // => map[k1:7] +_, prs := m["k2"] +fmt.Println(prs) // => false +n := map[string]int{"foo": 1, "bar": 2} +fmt.Println(n) // => map[bar:2 foo:1] +``` + +### 指向结构的指针 + +```go +v := &Vertex{1, 2} +v.X = 2 +``` + +Doing `v.X` is the same as doing `(*v).X`, when `v` is a pointer. + +Golang 函数 +-------- + +### 多个参数 + +```go +func plus(a int, b int) int { + return a + b +} +func plusPlus(a, b, c int) int { + return a + b + c +} +fmt.Println(plus(1, 2)) +fmt.Println(plusPlus(1, 2, 3)) +``` + +### 多次返回 + +```go +func vals() (int, int) { + return 3, 7 +} +a, b := vals() +fmt.Println(a) // => 3 +fmt.Println(b) // => 7 +``` + +### 匿名函数 + +```go +r1, r2 := func() (string, string) { + x := []string{"hello", "world"} + return x[0], x[1] +}() +// => hello world +fmt.Println(r1, r2) +``` + +### 命名返回 + +```go +func split(sum int) (x, y int) { + x = sum * 4 / 9 + y = sum - x + return +} +x, y := split(17) +fmt.Println(x) // => 7 +fmt.Println(y) // => 10 +``` + +### 变量函数 + +```go +func sum(nums ...int) { + fmt.Print(nums, " ") + total := 0 + for _, num := range nums { + total += num + } + fmt.Println(total) +} +sum(1, 2) //=> [1 2] 3 +sum(1, 2, 3) // => [1 2 3] 6 +nums := []int{1, 2, 3, 4} +sum(nums...) // => [1 2 3 4] 10 +``` + +### 初始化函数 + +```go +import --> const --> var --> init() +``` +--- + +```go +var num = setNumber() +func setNumber() int { + return 42 +} +func init() { + num = 0 +} +func main() { + fmt.Println(num) // => 0 +} +``` + +### 作为值的函数 + +```go +func main() { + // 将函数赋给名称 + add := func(a, b int) int { + return a + b + } + // 使用名称调用函数 + fmt.Println(add(3, 4)) // => 7 +} +``` + +### 关闭 1 + +```go +func scope() func() int{ + outer_var := 2 + foo := func() int {return outer_var} + return foo +} +// Outpus: 2 +fmt.Println(scope()()) +``` + +### 关闭 2 + +```go +func outer() (func() int, int) { + outer_var := 2 + inner := func() int { + outer_var += 99 + return outer_var + } + inner() + return inner, outer_var +} +inner, val := outer() +fmt.Println(inner()) // => 200 +fmt.Println(val) // => 101 +``` + +Golang 包(Packages) +-------- + +### 导入 + + +```go +import "fmt" +import "math/rand" +``` + +#### 等同于 + +```go +import ( + "fmt" // 给 fmt.Println + "math/rand" // 给 rand.Intn +) +``` + +另见：[导入](https://tour.golang.org/basics/1) + +### 别名 + + +```go +import r "math/rand" +``` + +--- + +```go +import ( + "fmt" + r "math/rand" +) +``` + +--- + +```go +r.Intn() +``` + +### Packages + +```go +package main +// 一个内部包只能被另一个包导入 +// 那是在以内部目录的父级为根的树内 +package internal +``` + +另见：[内部包](https://go.dev/doc/go1.4#internalpackages) + +### 导出名称 + +```go +// 以大写字母开头 +func Hello () { + ··· +} +``` + +另见：[导出的名称](https://tour.golang.org/basics/3) + +Golang 并发 +-------- + +### 协程 + + +```go +package main +import ( + "fmt" + "time" +) +func f(from string) { + for i := 0; i < 3; i++ { + fmt.Println(from, ":", i) + } +} +func main() { + f("direct") + go f("goroutine") + go func(msg string) { + fmt.Println(msg) + }("going") + time.Sleep(time.Second) + fmt.Println("done") +} +``` + +参见：[Goroutines](https://tour.golang.org/concurrency/1), [Channels](https://tour.golang.org/concurrency/2) + +### WaitGroup + + +```golang +package main +import ( + "fmt" + "sync" + "time" +) +func w(id int, wg *sync.WaitGroup) { + defer wg.Done() + fmt.Printf("%d starting\n", id) + time.Sleep(time.Second) + fmt.Printf("%d done\n", id) +} +func main() { + var wg sync.WaitGroup + for i := 1; i <= 5; i++ { + wg.Add(1) + go w(i, &wg) + } + wg.Wait() +} +``` + +参见：[WaitGroup](https://golang.org/pkg/sync/#WaitGroup) + +### Closing channels + +```go +ch <- 1 +ch <- 2 +ch <- 3 +close(ch) // 关闭频道 +``` + +--- + +```go +// 迭代通道直到关闭 +for i := range ch { + ··· +} +``` + +--- + +```go +// Closed if `ok == false` +v, ok := <- ch +``` + +参见：[范围和关闭](https://tour.golang.org/concurrency/4) + +### 缓冲通道 + +```go +ch := make(chan int, 2) +ch <- 1 +ch <- 2 +ch <- 3 +// 致命错误： +// 所有 goroutine 都处于休眠状态 - 死锁 +``` + +参见：[缓冲通道](https://tour.golang.org/concurrency/3) + +Golang 错误控制 +-------- + +### 延迟函数 + +```go +func main() { + defer func() { + fmt.Println("Done") + }() + fmt.Println("Working...") +} +``` + +### Lambda defer + +```go +func main() { + var d = int64(0) + defer func(d *int64) { + fmt.Printf("& %v Unix Sec\n", *d) + }(&d) + fmt.Print("Done ") + d = time.Now().Unix() +} +``` + +`defer` 函数使用当前值`d`，除非我们使用指针在 `main` 末尾获取最终值 + +### Defer + +```go +func main() { + defer fmt.Println("Done") + fmt.Println("Working...") +} +``` + +参见：[Defer, panic and recover](https://blog.golang.org/defer-panic-and-recover) + +Golang 方法(Methods) +-------- + + +### 接收器 + +```go +type Vertex struct { + X, Y float64 +} + +func (v Vertex) Abs() float64 { + return math.Sqrt(v.X * v.X + v.Y * v.Y) +} + +v := Vertex{1, 2} +v.Abs() +``` + +参见：[Methods](https://tour.golang.org/methods/1) + +### Mutation + +```go +func (v *Vertex) Scale(f float64) { + v.X = v.X * f + v.Y = v.Y * f +} + +v := Vertex{6, 12} +v.Scale(0.5) +// `v` 已更新 +``` + +参见：[指针接收器](https://tour.golang.org/methods/4) + +Golang 接口(Interfaces) +-------- + + +### 基本接口(Interfaces) + +```go +type Shape interface { + Area() float64 + Perimeter() float64 +} +``` + +### 结构(Struct) + +```go +type Rectangle struct { + Length, Width float64 +} +``` + +结构 `Rectangle` 通过实现其所有方法隐式实现接口 `Shape` + +### 方法(Methods) + +```go +func (r Rectangle) Area() float64 { + return r.Length * r.Width +} +func (r Rectangle) Perimeter() float64 { + return 2 * (r.Length + r.Width) +} +``` + +在 `Shape` 中定义的方法在`Rectangle`中实现 + +### 接口实例 + +```go +func main() { + var r Shape = Rectangle{Length: 3, Width: 4} + fmt.Printf("Type of r: %T, Area: %v, Perimeter: %v.", r, r.Area(), r.Perimeter()) +} +``` + + +杂项 +------------- + +### 关键字(Keywords) +- break +- default +- func +- interface +- select +- case +- defer +- go +- map +- struct +- chan +- else +- goto +- package +- switch +- const +- fallthrough +- if +- range +- type +- continue +- for +- import +- return +- var + + +### 运算符和标点符号 + +| | | | | | | | | | +|---|----|-----|-----|------|----|-----|---|---| +| `+` | & | += | &= | && | == | != | ( | ) | +| `-` | \| | -= | \|= | \|\| | < | <= | [ | ] | +| `*` | ^ | *= | ^= | <- | > | >= | { | } | +| `/` | << | /= | <<= | ++ | = | := | , | ; | +| `%` | >> | %= | >>= | -- | ! | ... | . | : | +| | &^ | &^= | | | | | | | + +另见 +-------- +- [Devhints](https://devhints.io/go) _(devhints.io)_ +- [A tour of Go](https://tour.golang.org/welcome/1) _(tour.golang.org)_ +- [Golang wiki](https://github.com/golang/go/wiki/) _(github.com)_ +- [Effective Go](https://golang.org/doc/effective_go.html) _(golang.org)_ +- [Go by Example](https://gobyexample.com/) _(gobyexample.com)_ +- [Awesome Go](https://awesome-go.com/) _(awesome-go.com)_ +- [JustForFunc Youtube](https://www.youtube.com/channel/UC_BzFbxG2za3bp5NRRRXJSw) _(youtube.com)_ +- [Style Guide](https://github.com/golang/go/wiki/CodeReviewComments) _(github.com)_ diff --git a/scripts/assets/golang.svg b/scripts/assets/golang.svg new file mode 100644 index 0000000..96d77fa --- /dev/null +++ b/scripts/assets/golang.svg @@ -0,0 +1 @@ + \ No newline at end of file