JSON解码器无法将一个对象解码为另一个对象。

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英文:

JSON Decoder cannot decode an object into an object

问题

以下是翻译好的内容:

type MiddleMan struct {
	User CompletedByUser `json:"user"`
}
type CompletedByUser struct {
	DisplayName string `json:"displayName"`
	Id          string `json:"id"`
}

使用上述类型我运行了以下代码

shorterJsonString := `{
	"user":{
		"displayName":null,
		"id":"a03dfee5-a754-4eb9"
	}
}`

if !json.Valid([]byte(shorterJsonString)) {
	log.Println("Not valid")
}
var middleMan models.MiddleMan

newReader := strings.NewReader(shorterJsonString)
json.NewDecoder(newReader).Decode(&middleMan)

log.Println(middleMan)

不幸的是解码器似乎对嵌套对象有问题打印输出的结果是

{{ a03dfee5-a754-4eb9 }}

它似乎将整个对象扁平化为id字段这是怎么回事
英文:
type MiddleMan struct {
	User CompletedByUser `json:"user"`
}
type CompletedByUser struct {
	DisplayName string `json:"displayName"`
	Id          string `json:"id"`
}

Using the following types, I run the code

shorterJsonString := `{
	"user":{
		"displayName":null,
		"id":"a03dfee5-a754-4eb9"
 	}
 }`

if !json.Valid([]byte(shorterJsonString)) {
	log.Println("Not valid")
}
var middleMan models.MiddleMan

newReader := strings.NewReader(shorterJsonString)
json.NewDecoder(newReader).Decode(&middleMan)

log.Println(middleMan)

Unfortunately, the decoder is seemingly broken for nested objects. Rather than spitting out actual objects, the print prints out

{{ a03dfee5-a754-4eb9 }}

It seems to flatten the whole thing into the id field. What is going on here?

答案1

得分: 4

你期望发生什么/打印什么?

log 包(使用 fmt 包)会打印用大括号括起来的结构体,字段值之间用空格分隔。

你的 MiddleMan 结构体只有一个字段,所以它看起来会像这样:

{field}

其中 field 是另一个类型为 CompletedByUserstruct,它有两个字段,所以它看起来会像这样:

{{field1 field2}}

其中 fieldstring 类型,是空字符串,所以你会看到 field2 的值前面有一个空格:

{{ a03dfee5-a754-4eb9}}

如果你打印时添加字段名:

log.Printf("%+v", middleMan)

你会看到如下输出:

{User:{DisplayName: Id:a03dfee5-a754-4eb9}}

使用另一种(Go 语法)格式:

log.Printf("%#v", middleMan)

输出:

main.MiddleMan{User:main.CompletedByUser{DisplayName:"", Id:"a03dfee5-a754-4eb9"}}

你可以在 Go Playground 上尝试这个。

英文:

What did you expect to happen / get printed?

The log package (which uses the fmt package) prints structs enclosed in braces, listing field values separated by spaces.

Your MiddleMan has a single field, so it'll look like this:

{field}

Where field is another struct of type CompletedByUser, which has 2 fields, so it'll look like this:

{{field1 field2}}

Where field is of string type, being the empty string, so you'll see the value of field2 prefixed with a space:

{{ a03dfee5-a754-4eb9}}

If you print it adding field names:

log.Printf("%+v", middleMan)

You'll see an output like:

{User:{DisplayName: Id:a03dfee5-a754-4eb9}}

Using another (Go-syntax) format:

log.Printf("%#v", middleMan)

Output:

main.MiddleMan{User:main.CompletedByUser{DisplayName:"", Id:"a03dfee5-a754-4eb9"}}

Try this on the Go Playground.

huangapple
  • 本文由 发表于 2021年12月1日 16:59:55
  • 转载请务必保留本文链接:https://go.coder-hub.com/70181451.html
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