Go语言学习笔记17.字符串和json处理

字符串处理

这里只展示了常用的，更多的可以去看文档。文档地址在第一篇里面有。

func Contains(s, substr string) bool
功能：字符串s中是否包含substr，返回bool值
fmt.Println(strings.Contains("seafood", "foo"))

func Join(a []string, sep string) string
功能：字符串链接，把slice a通过sep链接起来
s := []string{"foo", "bar", "baz"}
fmt.Println(strings.Join(s, ", "))
//运行结果:foo, bar, baz

func Split(s, sep string) []string
功能：把s字符串按照sep分割，返回slice
fmt.Printf("%q\n", strings.Split("a,b,c", ","))
//["a" "b" "c"]

func Index(s, sep string) int
功能：在字符串s中查找sep所在的位置，返回位置值，找不到返回-1
fmt.Println(strings.Index("chicken", "ken"))

func Repeat(s string, count int) string
功能：重复s字符串count次，最后返回拼接好的字符串
fmt.Println("ba" + strings.Repeat("na", 2))
//运行结果:banana

func Replace(s, old, new string, n int) string
功能：在s字符串中，把old字符串替换为new字符串，n表示替换的次数，小于0表示全部替换
fmt.Println(strings.Replace("oink oink oink", "oink", "moo", -1))

func Trim(s string, cutset string) string
功能：在s字符串的头部和尾部去除cutset指定的字符串
fmt.Printf("[%q]", strings.Trim(" !!! Achtung !!! ", "! "))
//运行结果:["Achtung"]

func Fields(s string) []string
功能：去除s字符串的空格符，并且按照空格分割返回slice
fmt.Printf("Fields are: %q", strings.Fields("  foo bar  baz   "))
//运行结果:Fields are: ["foo" "bar" "baz"]

字符串转换

Append 系列函数将整数等转换为字符串后，添加到现有的字节数组中。
str := make([]byte, 0, 100)
str = strconv.AppendInt(str, 4567, 10) //以10进制方式追加
str = strconv.AppendBool(str, false)
str = strconv.AppendQuote(str, "abcdefg")
str = strconv.AppendQuoteRune(str, '单')
fmt.Println(string(str)) //4567false"abcdefg"'单'

Format 系列函数把其他类型的转换为字符串。
a := strconv.FormatBool(false)
b := strconv.FormatInt(1234, 10)
c := strconv.FormatUint(12345, 10)
d := strconv.Itoa(1023)
fmt.Println(a, b, c, d) //false 1234 12345 1023

Parse 系列函数把字符串转换为其他类型。
a, err := strconv.ParseBool("false")
b, err := strconv.ParseFloat("123.23", 64)
c, err := strconv.ParseInt("1234", 10, 64)
d, err := strconv.ParseUint("12345", 10, 64)
e, err := strconv.Atoi("1023")
fmt.Println(a, b, c, d, e) //false 123.23 1234 12345 1023

正则表达式

package main

import (
    "fmt"
    "regexp"
)

func main() {

    buf := "abc azc a7c aac 888 a9c  tac a9c"

    //1) 解释规则, 它会解析正则表达式，如果成功返回解释器
    reg2 := regexp.MustCompile(`a.c`)
    fmt.Println("reg2 = ",reg2) //reg2 =  a.c
    reg3 := regexp.MustCompile(`a[0-9]c`)
    fmt.Println("reg3 = ",reg3)//reg3 =  a[0-9]c

    reg1 := regexp.MustCompile(`a\dc`)
    if reg1 == nil { //解释失败，返回nil
        fmt.Println("regexp err")
        return
    }

    //2) 返回符合规则的[]string切片,如果没有匹配到，会返回nil。
    result1 := reg1.FindAllStringSubmatch(buf, -1)
    fmt.Println("result1 = ", result1)//[[a7c] [a9c] [a9c]]

    result2 := reg1.FindAllString(buf, -1) 
    fmt.Println("result2 = ", result2)//[a7c a9c a9c]

}

在这里插入图片描述

json

package main

import (
    "encoding/json"
    "fmt"
)

//首字母是大写才会被输出
type IT struct {
    Company  string   `json:"-"`        //此字段不会输出到屏幕
    Subjects []string `json:"subjects"` //二次编码
    IsOk     bool     `json:",string"`  //会转换成string再输出到json
    Price    float64  `json:",string"`
    Type     int      `json:",omitempty"`//为空则不会输出
}

func main() {
    
    s := IT{"itcast", []string{"Go", "C++", "Python", "Test"}, true, 666.666,0}

    //编码，根据内容生成json文本
    buf, err := json.Marshal(s) //生成一段JSON格式的文本
    if err != nil {
        fmt.Println("err = ", err)
        return
    }
    fmt.Println("buf = ", string(buf)) 
    //buf =  {"subjects":["Go","C++","Python","Test"],"IsOk":"true","Price":"666.666"}   注意没有type

    s2 := IT{"itcast", []string{"Go", "C++", "Python", "Test"}, true, 666.666,1}

    buf2, err := json.MarshalIndent(s2, "", "   ") //格式化编码
    if err != nil {
        fmt.Println("err = ", err)
        return
    }
    fmt.Println("buf = ", string(buf2))
    /**
    buf =  {
        "subjects": [
                "Go",
                "C++",
                "Python",
                "Test"
        ],
        "IsOk": "true",
        "Price": "666.666",
        "Type": 1
    }
    */

}

map转json:

func main() {
    //创建一个map
    m := make(map[string]interface{}, 4)
    m["company"] = "itcast"
    m["subjects"] = []string{"Go", "C++", "Python", "Test"}
    m["isok"] = true
    m["price"] = 666.666

    //编码成json
    //result, err := json.Marshal(m)
    result, err := json.MarshalIndent(m, "", "  ")
    if err != nil {
        fmt.Println("err = ", err)
        return
    }
    fmt.Println("result = ", string(result))
}

json转结构体

package main

import (
    "encoding/json"
    "fmt"
)

type IT struct {
    Company  string   `json:"company"`
    Subjects []string `json:"subjects"` //二次编码
    IsOk     bool     `json:"isok"`
    Price    float64  `json:"price"`
}

type IT2 struct {
    Subjects []string `json:"subjects"` //二次编码
}

func main() {

    jsonBuf := `
            {
            "company": "itcast",
            "subjects": [
                "Go",
                "C++",
                "Python",
                "Test"
            ],
            "isok": true,
            "price": 666.666
        }`

    var tmp IT                                   //定义一个结构体变量
    err := json.Unmarshal([]byte(jsonBuf), &tmp) //第二个参数要地址传递
    if err != nil {
        fmt.Println("err = ", err)
        return
    }
    fmt.Printf("tmp = %+v\n", tmp) //tmp = {Company:itcast Subjects:[Go C++ Python Test] IsOk:true Price:666.666}

    //只接受部分数据
    var tmp2 IT2
    err = json.Unmarshal([]byte(jsonBuf), &tmp2) //第二个参数要地址传递
    if err != nil {
        fmt.Println("err = ", err)
        return
    }
    fmt.Printf("tmp2 = %+v\n", tmp2)

}

json转map

    m := make(map[string]interface{}, 4)

    err := json.Unmarshal([]byte(jsonBuf), &m) //第二个参数要地址传递
    if err != nil {
        fmt.Println("err = ", err)
        return
    }
    fmt.Printf("m = %+v\n", m) //m = map[company:itcast isok:true price:666.666 subjects:[Go C++ Python Test]]