第05天(异常、文本文件处理)_03

11_通过结构体生成json.go

package main

import (
    "encoding/json"
    "fmt"
)

/*

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

*/

//成员变量名首字母必须大写
//type IT struct {
//  Company  string
//  Subjects []string
//  IsOk     bool
//  Price    float64
//}

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"`
    Price    float64  `json:",string"`
}

func main() {
    //定义一个结构体变量，同时初始化
    s := IT{"itcast", []string{"Go", "C++", "Python", "Test"}, true, 666.666}

    //编码，根据内容生成json文本
    //{"Company":"itcast","Subjects":["Go","C++","Python","Test"],"IsOk":true,"Price":666.666}
    //buf, err := json.Marshal(s)
    buf, err := json.MarshalIndent(s, "", " ") //格式化编码
    if err != nil {
        fmt.Println("err = ", err)
        return
    }

    fmt.Println("buf = ", string(buf))
}

12_通过map生成json.go

package main

import (
    "encoding/json"
    "fmt"
)

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))
}

13_json解析到结构体.go

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"`
}

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.Println("tmp = ", tmp)
    fmt.Printf("tmp = %+v\n", tmp)

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

    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)
}

14_json解释到map.go

package main

import (
    "encoding/json"
    "fmt"
)

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

    //创建一个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)

    //  var str string
    //  str = string(m["company"]) //err， 无法转换
    //  fmt.Println("str = ", str)

    var str string

    //类型断言, 值，它是value类型
    for key, value := range m {
        //fmt.Printf("%v ============> %v\n", key, value)
        switch data := value.(type) {
        case string:
            str = data
            fmt.Printf("map[%s]的值类型为string, value = %s\n", key, str)
        case bool:
            fmt.Printf("map[%s]的值类型为bool, value = %v\n", key, data)
        case float64:
            fmt.Printf("map[%s]的值类型为float64, value = %f\n", key, data)
        case []string:
            fmt.Printf("map[%s]的值类型为[]string, value = %v\n", key, data)
        case []interface{}:
            fmt.Printf("map[%s]的值类型为[]interface, value = %v\n", key, data)
        }
    }
}