arrays - json 解码后缺少结构对象的嵌套数组

Question

当对象具有嵌套的结构对象数组时，我在将字符串解码回结构对象时遇到了一些问题。我使用以下代码作为我的问题的演示:

json字符串为

const myStr = `{
  "name": "test_session1",
  "shared_items:": [
    {
      "id": 0,
      "name": ".aspnet"
    },
    {
      "id": 1,
      "name": ".bash_profile"
    }
  ]
}`

我有两个结构如下，Session 是父结构，SharedItem 是关联的子结构(ren):

type Session struct {
    ID              uint64           `json:"id"`
    Name            string           `json:"name,omitempty"`
    SharedItems     []SharedItem `json:"shared_items"`
}

type SharedItem struct {
    ID          uint64 `json:"id"`
    Name        string `json:"name"`
}

我尝试了以下方法来解码 json 字符串，但看起来 SharedItem 对象的嵌套数组丢失了，因为我看到 sess 对象有 0 共享项目，这不是我所期望的。

func main() {
    var sess Session
    if err := json.Unmarshal([]byte(myStr), &sess); err != nil {
        panic(err)
    }
    fmt.Printf("sess name is: %s, and has %d shared items\n", sess.Name, len(sess.SharedItems)) // printed: sess name is test_session1, and has 0 shared items
}

这是我的 go playground 的链接:https://play.golang.org/p/a-y5T3tut6g

Answer 1

json 解码的 Golang 规范描述了这一切

To unmarshal JSON into a struct, Unmarshal matches incoming object keys to the keys used by Marshal (either the struct field name or its tag), preferring an exact match but also accepting a case-insensitive match. By default, object keys which don't have a corresponding struct field are ignored (see Decoder.DisallowUnknownFields for an alternative).

在 json 中，共享项目的 json 对象有 : 冒号，我们可以看到它是 shared_items: 而不是 shared_items是我们的json标签

  "shared_items:": [
    {
      "id": 0,
      "name": ".aspnet"
    },
    {
      "id": 1,
      "name": ".bash_profile"
    }
  ]

要么删除 : 要么附加到你的 struct json 标签中以匹配相同的标签。

package main

import (
    "fmt"
    "encoding/json"
)

type Session struct {
    Name            string           `json:"name,omitempty"`
    SharedItems     []SharedItem    `json:"shared_items"`
}

type SharedItem struct {
    ID          uint64 `json:"id"`
    Name        string `json:"name"`
}

const myStr = `{"name":"test_session1","shared_items":[{"id":0,"name":".aspnet"},{"id":1,"name":".bash_profile"}]}`

func main() {
    var sess Session

    if err := json.Unmarshal([]byte(myStr), &sess); err != nil {
        panic(err)
    }
    fmt.Println(sess)
    fmt.Printf("sess name is: %s, and has %d shared items\n", sess.Name, len(sess.SharedItems))
}

Playground example