英文:
Converting Go struct to JSON
问题
我正在尝试使用json包将Go结构体转换为JSON，但我得到的结果只有{}。我确定这是一个非常明显的问题，但我没有看到它。
package main
import (
"fmt"
"encoding/json"
)
type User struct {
name string
}
func main() {
user := &User{name:"Frank"}
b, err := json.Marshal(user)
if err != nil {
fmt.Printf("Error: %s", err)
return;
}
fmt.Println(string(b))
}
然后当我尝试运行它时，我得到这个结果：
$ 6g test.go && 6l -o test test.6 && ./test
{}
<details>
<summary>英文:</summary>
I am trying to convert a Go struct to JSON using the `json` package but all I get is `{}`. I am certain it is something totally obvious but I don't see it.
package main
import (
"fmt"
"encoding/json"
)
type User struct {
name string
}
func main() {
user := &User{name:"Frank"}
b, err := json.Marshal(user)
if err != nil {
fmt.Printf("Error: %s", err)
return;
}
fmt.Println(string(b))
}
Then when I try to run it I get this:
$ 6g test.go && 6l -o test test.6 && ./test
{}
</details>
# 答案1
**得分**: 518
你需要[导出][1] `User.name` 字段，以便 `json` 包可以访问它。将 `name` 字段重命名为 `Name`。
package main
import (
"fmt"
"encoding/json"
)
type User struct {
Name string
}
func main() {
user := &User{Name: "Frank"}
b, err := json.Marshal(user)
if err != nil {
fmt.Println(err)
return
}
fmt.Println(string(b))
}
输出：
{"Name":"Frank"}
[1]: http://golang.org/doc/go_spec.html#Exported_identifiers
<details>
<summary>英文:</summary>
You need to [export][1] the `User.name` field so that the `json` package can see it. Rename the `name` field to `Name`.
package main
import (
"fmt"
"encoding/json"
)
type User struct {
Name string
}
func main() {
user := &User{Name: "Frank"}
b, err := json.Marshal(user)
if err != nil {
fmt.Println(err)
return
}
fmt.Println(string(b))
}
Output:
{"Name":"Frank"}
[1]: http://golang.org/doc/go_spec.html#Exported_identifiers
</details>
# 答案2
**得分**: 93
相关问题：
我在将结构体转换为JSON时遇到了麻烦，然后通过Golang将其作为响应发送，然后通过Ajax在JavaScript中捕获相同的问题。
浪费了很多时间，所以在这里发布解决方案。
在Go中：
// web服务器
type Foo struct {
Number int `json:"number"`
Title string `json:"title"`
}
foo_marshalled, err := json.Marshal(Foo{Number: 1, Title: "test"})
fmt.Fprint(w, string(foo_marshalled)) // 将响应写入ResponseWriter (w)
在JavaScript中：
// 通过Ajax/其他方式调用并在"data"中接收
var Foo = JSON.parse(data);
console.log("number: " + Foo.number);
console.log("title: " + Foo.title);
<details>
<summary>英文:</summary>
Related issue:
I was having trouble converting struct to JSON, sending it as response from Golang, then, later catch the same in JavaScript via Ajax.
Wasted a lot of time, so posting solution here.
In Go:
// web server
type Foo struct {
Number int `json:"number"`
Title string `json:"title"`
}
foo_marshalled, err := json.Marshal(Foo{Number: 1, Title: "test"})
fmt.Fprint(w, string(foo_marshalled)) // write response to ResponseWriter (w)
In JavaScript:
// web call & receive in "data", thru Ajax/ other
var Foo = JSON.parse(data);
console.log("number: " + Foo.number);
console.log("title: " + Foo.title);
</details>
# 答案3
**得分**: 13
这是一个有趣的问题，使用新的go版本非常容易。你应该这样做：
```go
package main
import (
"fmt"
"encoding/json"
)
type User struct {
Name string `json:"name"`
}
func main() {
user := &User{Name:"Frank"}
b, err := json.Marshal(user)
if err != nil {
fmt.Printf("Error: %s", err)
return;
}
fmt.Println(string(b))
}
将这个名字改为Name。
英文:
This is an interesting question, it is very easy using the new go versions. You should do this:
package main
import (
"fmt"
"encoding/json"
)
type User struct {
Name string `json:"name"`
}
func main() {
user := &User{name:"Frank"}
b, err := json.Marshal(user)
if err != nil {
fmt.Printf("Error: %s", err)
return;
}
fmt.Println(string(b))
}
Change this name to Name.
答案4
得分: 8
你可以定义自己的自定义MarshalJSON和UnmarshalJSON方法，并有意地控制应该包含什么，例如：
package main
import (
"fmt"
"encoding/json"
)
type User struct {
name string
}
func (u *User) MarshalJSON() ([]byte, error) {
return json.Marshal(&struct {
Name string `json:"name"`
}{
Name: "customized" + u.name,
})
}
func main() {
user := &User{name: "Frank"}
b, err := json.Marshal(user)
if err != nil {
fmt.Println(err)
return
}
fmt.Println(string(b))
}
英文:
You can define your own custom MarshalJSON and UnmarshalJSON methods and intentionally control what should be included, ex:
package main
import (
"fmt"
"encoding/json"
)
type User struct {
name string
}
func (u *User) MarshalJSON() ([]byte, error) {
return json.Marshal(&struct {
Name string `json:"name"`
}{
Name: "customized" + u.name,
})
}
func main() {
user := &User{name: "Frank"}
b, err := json.Marshal(user)
if err != nil {
fmt.Println(err)
return
}
fmt.Println(string(b))
}
</details>
# 答案5
**得分**: 7
结构体值被编码为JSON对象。除非满足以下条件，否则每个导出的结构体字段都成为对象的成员：
- 字段的标签是“-”，或者
- 字段为空并且其标签指定了“omitempty”选项。
空值包括false、0、任何nil指针或接口值，以及长度为零的任何数组、切片、映射或字符串。对象的默认键字符串是结构体字段名，但可以在结构体字段的标签值中指定。结构体字段的标签值中的“json”键是键名，后面可以跟一个可选的逗号和选项。
<details>
<summary>英文:</summary>
Struct values encode as JSON objects. Each exported struct field becomes
a member of the object unless:
- the field's tag is "-", or
- the field is empty and its tag specifies the "omitempty" option.
The empty values are false, 0, any nil pointer or interface value, and any array, slice, map, or string of length zero. The object's default key string is the struct field name but can be specified in the struct field's tag value. The "json" key in the struct field's tag value is the key name, followed by an optional comma and options.
</details>
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