Golang入门学习（四）：常用的函数汇总

文章目录

- 2.4 常用的内置函数

2.4 常用的内置函数

2.4.1 字符串常用内置函数

https://golang.org/pkg/strings/
https://golang.org/pkg/strconv/
统计字符串长度的函数：len(str)
字符串遍历，同时处理有中文的问题：r:=[]rune(str)

字符串转整数：strconv(str), strconv.ParseInt()

func strconvDemo() {

	v := "10"

	if s, err := strconv.Atoi(v); err == nil {

		fmt.Printf("%T, %v", s, s)

	}

}

整数转字符串：strconv(str)

func strItoa(){

	i := 10

	s := strconv.Itoa(i)

	fmt.Printf("%T, %v\n", s, s)

}

字符串转成byte切片：bytes := []byte("asdfgh"))
byte切片转换成字符串: str4 := string([]byte{67, 68, 69, 70, 72})

10进制数转换为其他进制数(转换后为字符串类型): str = strconv.FromatInt(123, 2)

func ten2others(){

	s10 := strconv.FormatInt(v2, 10)

	fmt.Printf("%T, %v\n", s10, s10)

	s16 := strconv.FormatInt(v2, 16)

	fmt.Printf("%T, %v\n", s16, s16)

}

查找字符串中是否包含指定字符串： strings.Contains("seafood","food")
统计字符串中子字符串的个数： strings.Count("aaaaaaa","a")
忽略大小写的字符串比较函数： strings.EqualFold("Chinese","chinese")
查找子字符串第一次出现的位置：strings.Index("stringsGolang","lang")
查找子字符串最后一次出现的位置：strings.LastIndex("stringsGolang","lang")
替换指定字符串: strings.Replace("Go Go Go", "Go", "Golang", 1)
按指定字符分割字符串: strings.Split("Hello 北京成都上海深圳", " ")
字符串大小写转换: strings.ToLower、strings.ToUpper
去除字符串左右两端的指定字符(无法去除字符串内部的字符)：strings.Trim(" aaaaaaaaaC__", " _")
判断一个字符串是否以指定字符串开头: func HasPrefix(s, prefix string) bool
判断一个字符串是否以指定字符串结尾：func HasSuffix(s, suffix string) bool

2.4.2 常用的时间和日期相关函数

https://golang.org/pkg/time/
时间、日期相关函数需要导入time包

获取当前时间：

func getTime(){

	//1. 获取当前时间

	now := time.Now()

	fmt.Printf("Now = %v  Type=%T", now, now)

	//Now = 2021-02-23 16:14:42.0211031 +0800 CST m=+0.000997301  Type=time.Time

}

获取当前时间的详细信息：

func detail(){

	//2.获取年月日时分秒

	now := time.Now()

	fmt.Printf("年=%v\n", now.Year())

	fmt.Printf("月=%v\n", now.Month())

	fmt.Printf("日=%v\n", int(now.Day()))

	fmt.Printf("时=%v\n", now.Hour())

	fmt.Printf("分=%v\n", now.Minute())

	fmt.Printf("秒=%v\n", now.Second())

}

格式化时间格式：(format的字符串数值是固定的，必须是2006/01/02 15:04:05)

func timeFormat(){

	now := time.Now()

	fmt.Println(now.Format("2006/01/02 15:04:05"))

	fmt.Println(now.Format("2006-01-02"))

	fmt.Println(now.Format("15:04:05"))

}

时间常量：

const (

	Nanosecond  Duration = 1

	Microsecond          = 1000 * Nanosecond

	Millisecond          = 1000 * Microsecond

	Second               = 1000 * Millisecond

	Minute               = 60 * Second

	Hour                 = 60 * Minute

)

const (

	ANSIC       = "Mon Jan _2 15:04:05 2006"

	UnixDate    = "Mon Jan _2 15:04:05 MST 2006"

	RubyDate    = "Mon Jan 02 15:04:05 -0700 2006"

	RFC822      = "02 Jan 06 15:04 MST"

	RFC822Z     = "02 Jan 06 15:04 -0700" // RFC822 with numeric zone

	RFC850      = "Monday, 02-Jan-06 15:04:05 MST"

	RFC1123     = "Mon, 02 Jan 2006 15:04:05 MST"

	RFC1123Z    = "Mon, 02 Jan 2006 15:04:05 -0700" // RFC1123 with numeric zone

	RFC3339     = "2006-01-02T15:04:05Z07:00"

	RFC3339Nano = "2006-01-02T15:04:05.999999999Z07:00"

	Kitchen     = "3:04PM"

	// Handy time stamps.

	Stamp      = "Jan _2 15:04:05"

	StampMilli = "Jan _2 15:04:05.000"

	StampMicro = "Jan _2 15:04:05.000000"

	StampNano  = "Jan _2 15:04:05.000000000"

)

结合sleep来使用时间常量

func sleepDemo(){

	for {

		fmt.Println(time.Now().Second())

		time.Sleep(time.Millisecond * 100)

	}

}

获取当前unix时间戳

func getUnixTime(){

	fmt.Println(time.Now().Unix())

	fmt.Println(time.Now().UnixNano())

}

2.4.3 内置函数

https://golang.org/pkg/builtin/ /内建函数/
len(): 获取字符串长度的函数:
new(): 用来分配内存，主要用来分配值类型，如int, float64,
make(): 用来分配内存，主要分配引用类型的内存, 如切片，channel, map等

func main() {

	num1 := 100

	fmt.Printf("num1的类型为：%T， num1的值为：%d, num1的地址为：%p\n", num1, num1, &num1)

	num2 := new(int) /*new的返回值是一个指针*/

	fmt.Printf("num2的类型为：%T， num2的值为：%d, num2的地址为：%p\n", num2, *num2, &num2)

}

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