go - 如何将我的 2d 字符串片段转换为 []byte？

Question

我已经创建了一个 2d slice 并从后端数据库填充它，但是由于 json.Unmarshal 只接受 []byte 作为第一个参数我如何将我的 2d slice 转换为 []byte。

这里是引用示例代码，因为我不能分享内部代码:

package main

import (
    "encoding/json"
    "fmt"
    "io/ioutil"
    "net/http"
)

//User sjd
type User struct {
    EmailList [][]string `json:"emailList"`
}

func listHandler(w http.ResponseWriter, r *http.Request) {
    reqBody, _ := ioutil.ReadAll(r.Body)
    var user User
    json.Unmarshal(reqBody, &user)
    el := user.EmailList 
    keys := make([][]string, 0)
    json.Unmarshal([]byte(el), &keys) //this line not working because []byte(el) not possible
    fmt.Println(keys)
    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(http.StatusOK)
    w.Write([]byte(el))//this line not working because []byte(el) not possible
}

func main() {
    http.HandleFunc("/", listHandler)
    http.ListenAndServe(":8080", nil)
}

示例请求:

{
    "emailList": [
        [
            "akki@gmail.com",
            "bakki@gmail.com"
        ],
        [
            "lakki@gmail.com",
            "jakki@gmail.com"
        ]
    ]
}

Answer 1

Unmarshal JSON 作为 []byte 给 user。 Marshal user.EmailList 到 JSON 作为 []byte。例如，

package main

import (
    "encoding/json"
    "fmt"
    "os"
)

type User struct {
    EmailList [][]string `json:"emailList"`
}

func main() {
    // rBody, err := ioutil.ReadAll(r.Body)
    rBody := []byte(`
{
    "emailList": [
        [
            "akki@gmail.com",
            "bakki@gmail.com"
        ],
        [
            "lakki@gmail.com",
            "jakki@gmail.com"
        ]
    ]
}
    `)
    fmt.Println(string(rBody))

    var user User
    err := json.Unmarshal(rBody, &user)
    if err != nil {
        fmt.Fprintln(os.Stderr, err)
        return
    }
    fmt.Println(user.EmailList)

    wData, err := json.Marshal(user.EmailList) // wData is []byte
    if err != nil {
        fmt.Fprintln(os.Stderr, err)
        return
    }
    fmt.Println(wData) // wData is []byte
    fmt.Println(string(wData))
    // _, err = w.Write(wData)
}

Playground :https://play.golang.org/p/S3HWiTqz--B

输出:

{
    "emailList": [
        [
            "akki@gmail.com",
            "bakki@gmail.com"
        ],
        [
            "lakki@gmail.com",
            "jakki@gmail.com"
        ]
    ]
}

[[akki@gmail.com bakki@gmail.com] [lakki@gmail.com jakki@gmail.com]]
[91 91 34 97 107 107 105 64 103 109 97 105 108 46 99 111 109 34 44 34 98 97 107 107 105 64 103 109 97 105 108 46 99 111 109 34 93 44 91 34 108 97 107 107 105 64 103 109 97 105 108 46 99 111 109 34 44 34 106 97 107 107 105 64 103 109 97 105 108 46 99 111 109 34 93 93]
[["akki@gmail.com","bakki@gmail.com"],["lakki@gmail.com","jakki@gmail.com"]]