kaisawind's blog

go一些技巧

map第二个返回值 go语言的map有第二个返回值，能够判断在map中key是否存在

value, ok := kv[key]
if !ok {
    // do something
}

_无视其中一个值使用_可以无视多个值中的其中几个或全部

_, ok := kv[key]
if !ok {
    // do something
}

无视全部值

_, _ := kv[key]

在切片后追加元素

var arr []int
arr = append(arr, 1)

在切片前追加元素

var arr []int
arr = append([]int{1}, arr...)

在切片后追加多个元素

var arr []int
arr = append(arr, []int{1, 2, 3, 4, 5}...)

切片越界不会越界，是空切片

fmt.Println(arr[len(arr):])

会越界

fmt.Println(arr[len(arr)+1:])

会越界

fmt.Println(arr[len(arr)])

弃用标记

// Execer is an optional interface that may be implemented by a Conn.
//
// If a Conn does not implement Execer, the sql package's DB.Exec will
// first prepare a query, execute the statement, and then close the
// statement.
//
// Exec may return ErrSkip.
//
// Deprecated: Drivers should implement ExecerContext instead (or additionally).
type Execer interface {
    Exec(query string, args []Value) (Result, error)
}

BUG标记

// BUG(who): 我是bug说明

包注释单独doc.go文件

package aaa
// Execer is an optional interface that may be implemented by a Conn.
//
// If a Conn does not implement Execer, the sql package's DB.Exec will
// first prepare a query, execute the statement, and then close the
// statement.
//
// Exec may return ErrSkip.

Example 文件名example_xxx_test.go 包名xxx_test 函数名func Example[FuncName][_tag]() 函数尾 // Output:

// 文件必须放在 banana包目录下, 名字必须为example_xxx_test.go
// Package banana_test 为banana包的示例
package banana_test
// 此注释将会被展示在页面上
// 此函数将被展示在OverView区域
func Example() {
    fmt.Println("Hello OverView")
    
    // Output:
    // Hello OverView
}

UnitTest 文件名xxx_test.go 包名xxx_test 函数名func Test[FuncName][_tag]()

package server_test
import (
    "testing"
    "time"
)
func TestServerTimeLayout1(t *testing.T) {
    some := time.Now().Format(types.TimeLayout1)
    t.Log(some)
}

BenchmarkTest 文件名xxx_test.go 包名xxx_test 函数名func Benchmark[FuncName][_tag]()

package types_test
func BenchmarkDataMarshal(b *testing.B) {
    for i := 0; i < b.N; i++ {
        data := Data{
            MsgType: DeviceReq,
            Data: []*DeviceS{
                {
                    DeviceID:  "abc-123_&%S",
                    ServiceID: "discrete",
                    EventTime: "123456",
                    Data: map[string]interface{}{
                        "LD_14.XY": "0",
                        "LD_15.XY": 0,
                        "LD_16.XY": int64(64),
                        "LD_17.XY": true,
                        "LD_18.XY": 123.456,
                    },
                },
            },
        }
        _, err := json.Marshal(data)
        if err != nil {
            b.FailNow()
        }
        // fmt.Println("json", string(bytes))
    }
}

交换数据

func max(a, b int) {
    if a > b {
        a, b = b, a
    }
}

函数返回值定义

func swap(a, b int) (max, min int) {
    if a > b {
        max, min = a, b
    } else {
        max, min = b, a
    }
    return
}

safe delete in range

m := map[string]string{
    "1": "one",
    "2": "two",
    "3": "three",
}
for key, v := range m {
    delete(m, key)
}

switch可以无参

switch {
    case a == 3:
    case b == 4:
    case c == 7:
}

channel写数据时使用default防lock

select {
    case <-quit:
    case data<-event:
    default:
}

无类型结构体

// Info 请求可变更字段
type Info struct {
	DNSNames []string `json:"dns"` // 证书认证dns
	Duration struct {
		Year  int `json:"year"`
		Month int `json:"month"`
		Day   int `json:"day"`
	} `json:"duration"` // 证书有效时间
	Path struct {
		Servers []struct {
			Cert string `json:"cert"`
			Key  string `json:"key"`
		} `json:"servers"`
		Clients []struct {
			Cert string `json:"cert"`
			Key  string `json:"key"`
		} `json:"clients"`
	} `json:"path"`
}

初始化与结构体声明在一起

var opts = struct {
	PrintVersion func() `short:"v" long:"version" description:"print the version of the iotx"`
	EnableDebug  func() `short:"d" long:"debug" description:"enable debug of the iotx"`
}{
	PrintVersion: func() {
		fmt.Println("Version:", Version)
		fmt.Println("BuildTime:", BuildTime)
		os.Exit(0)
	},
	EnableDebug: func() {
		logrus.SetLevel(logrus.DebugLevel)
	},
}

go一些技巧 - Mon, Jun 15, 2020