From 51fe88daad280a84d85fcbd18e31abee50bf7b6d Mon Sep 17 00:00:00 2001 From: jaywcjlove Date: Sat, 15 Oct 2022 19:36:05 +0000 Subject: [PATCH] feat: add `golang.md` sheatsheet. 19caaad57477cc85341a4277edf1b369b37403f5 --- docs/golang.html | 880 +++++++++++++++++++++++++++++++++++++++++++++++ index.html | 1 + 2 files changed, 881 insertions(+) create mode 100644 docs/golang.html diff --git a/docs/golang.html b/docs/golang.html new file mode 100644 index 00000000..9ddcb7ed --- /dev/null +++ b/docs/golang.html @@ -0,0 +1,880 @@ + + + + +Golang 备忘清单 + & golang cheatsheet & Quick Reference + + + + + + +

Golang 备忘清单

+

该备忘单提供了帮助您使用 Golang 的基本语法和方法。

+

入门

+
+
package main
+import "fmt"
+func main() {
+    fmt.Println("Hello, world!")
+}
+
+

直接运行

+
$ go run hello.go
+Hello, world!
+
+

或者在 Go repl 中尝试一下

+

变量

+
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

+
s1 := "Learn Go!"        // string
+b, c := 1, 2             // int
+d := true                // bool
+
+

参见：基本类型

+

函数

+
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)

+

注释

+
// 单行注释
+/* 这是
+多行注释 */
+
+

如果语句

+
if true {
+  fmt.Println("Yes!")
+}
+
+

参见：条件控制

+

Golang 基本类型

+

字符串 Strings

+
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

+
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

+
x := 5
+x++
+fmt.Println("x + 4 =", x + 4)
+fmt.Println("x * 4 =", x * 4) 
+
+

参见：更多操作符

+

布尔值 Booleans

+
isTrue   := true
+isFalse  := false
+
+

操作符

+
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

+

数组 Arrays

+ +
┌────┬────┬────┬────┬─────┬─────┐
+| 2  | 3  | 5  | 7  | 11  | 13  |
+└────┴────┴────┴────┴─────┴─────┘
+  0    1    2    3     4     5
+
+
+
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])
+
+
+
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

+
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)

+
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)

+

切片(Slices)

+
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

+

常量(Constants)

+
const s string = "constant"
+const Phi = 1.618
+const n = 500000000
+const d = 3e20 / n
+fmt.Println(d)
+
+

类型转换

+
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？

+
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

+
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

+ +
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

+

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

+
a := 10
+if a > 20 {
+    fmt.Println(">")
+} else if a < 20 {
+    fmt.Println("<")
+} else {
+    fmt.Println("=")
+}
+
+

if 中的语句

+
x := "hello go!"
+if count := len(x); count > 0 {
+    fmt.Println("Yes")
+}
+
+
+
if _, err := doThing(); err != nil {
+    fmt.Println("Uh oh")
+}
+
+

Switch

+
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

+

For loop

+
for i := 0; i <= 10; i++ {
+  fmt.Println("i: ", i)
+}
+
+

对于 Range 循环

+
nums := []int{2, 3, 4}
+sum := 0
+for _, num := range nums {
+  sum += num
+}
+fmt.Println("sum:", sum)
+
+

While 循环

+
i := 1
+for i <= 3 {
+  fmt.Println(i)
+  i++
+}
+
+

Continue 关键字

+
for i := 0; i <= 5; i++ {
+  if i % 2 == 0 {
+      continue
+  }
+  fmt.Println(i)
+}
+
+

Break 关键字

+
for {
+  fmt.Println("loop")
+  break
+}
+
+

Golang 结构和映射

+

定义

+ +
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)

+

字面量

+
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

+ +
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

+
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

+
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

+
func vals() (int, int) {
+  return 3, 7
+}
+a, b := vals()
+fmt.Println(a)    // => 3
+fmt.Println(b)    // => 7
+
+

匿名函数

+
r1, r2 := func() (string, string) {
+    x := []string{"hello", "world"}
+    return x[0], x[1]
+}()
+// => hello world
+fmt.Println(r1, r2)
+
+

命名返回

+
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

+
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

+
import --> const --> var --> init()
+
+
+
var num = setNumber()
+func setNumber() int {
+  return 42
+}
+func init() {
+  num = 0
+}
+func main() {
+  fmt.Println(num) // => 0
+}
+
+

作为值的函数

+
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

+
func scope() func() int{
+  outer_var := 2
+  foo := func() int {return outer_var}
+  return foo
+}
+// Outpus: 2
+fmt.Println(scope()())
+
+

关闭 2

+
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

+ +
import "fmt"
+import "math/rand"
+
+

等同于

+
import (
+  "fmt"        // 给 fmt.Println
+  "math/rand"  // 给 rand.Intn
+)
+
+

另见：导入

+

别名

+ +
import r "math/rand"
+
+
+
import (
+    "fmt"
+    r "math/rand"
+)
+
+
+
r.Intn()
+
+

Packages

+
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

+

导出名称

+
// 以大写字母开头
+func Hello () {
+  ···
+}
+
+

另见：导出的名称

+

Golang 并发

+

协程

+ +
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, Channels

+

WaitGroup

+ +
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

+

Closing channels

+
ch <- 1
+ch <- 2
+ch <- 3
+close(ch) // 关闭频道
+
+
+
// 迭代通道直到关闭
+for i := range ch {
+  ···
+}
+
+
+
// Closed if `ok == false`
+v, ok := <- ch
+
+

参见：范围和关闭

+

缓冲通道

+
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

+

Golang 错误控制

+

延迟函数

+
func main() {
+  defer func() {
+    fmt.Println("Done")
+  }()
+  fmt.Println("Working...")
+}
+
+

Lambda defer

+
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

+
func main() {
+  defer fmt.Println("Done")
+  fmt.Println("Working...")
+}
+
+

参见：Defer, panic and recover

+

Golang 方法(Methods)

+ +

接收器

+
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

+

Mutation

+
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

+

Golang 接口(Interfaces)

+ +

基本接口(Interfaces)

+
type Shape interface {
+  Area() float64
+  Perimeter() float64
+}
+
+

结构(Struct)

+
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)

+
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

+
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

+ +
+ diff --git a/index.html b/index.html index e7fa4b88..d7df153c 100644 --- a/index.html +++ b/index.html @@ -54,6 +54,7 @@ Dockerfile +Golang