JSON解组整数字段为字符串 [英] JSON unmarshal integer field into a string

问题描述

我正在努力将整数反序列化为字符串struct字段. struct字段是一个字符串，应该可以从我的库的用户中分配.这就是为什么我希望它是一个字符串，因为出于将其写入数据库的目的，我实际上并不关心其中的值. 用户可以提供文本，但有些用户只分配整数.

考虑此结构:

type Test struct {
  Foo string
}

有时候，我最终得到一个有效的JSON值，但由于Foo字段是整数而不是字符串，因此不会反序列化为struct:

{ "foo": "1" } // works
{ "foo": 1 } // doesn't

json.Unmarshal将爆炸并显示以下错误: json: cannot unmarshal number into Go struct field test.Foo of type string

查看复制品: https://play.golang.org/p/4Qau3umaVm

到目前为止，到目前为止，在我使用过的所有其他JSON库(使用其他语言)中，如果目标字段是字符串，并且您得到一个整数，则反序列化程序通常会将int封装在字符串中并用它来完成.可以在Go中实现吗?

由于我无法真正控制数据的输入方式，因此我需要使json.Unmarshal对此不敏感-另一个解决方案是将Foo定义为interface{}，这会不必要地使我的代码与类型断言等复杂化. /p>

关于如何执行此操作的任何想法?我基本上需要json:",string"

的反函数

解决方案

要处理大型结构，可以使用嵌入.

已更新为不会丢弃以前可能设置的字段值.

func (t *T) UnmarshalJSON(d []byte) error {
    type T2 T // create new type with same structure as T but without its method set!
    x := struct{
        T2 // embed
        Foo json.Number `json:"foo"`
    }{T2: T2(*t)} // don't forget this, if you do and 't' already has some fields set you would lose them

    if err := json.Unmarshal(d, &x); err != nil {
        return err
    }
    *t = T(x.T2)
    t.Foo = x.Foo.String()
    return nil
}

https://play.golang.org/p/BytXCeHMvt

I am struggling with deserializing a integer into a string struct field. The struct field is a string and is expected to be assignable from users of my library. That's why I want it to be a string, since for the purpose of writing it to the database I actually don't care about the value inside. The users can supply text, but some just assign integers.

Consider this struct:

type Test struct {
  Foo string
}

Sometimes I end up with a JSON value that is valid but won't deserialize into the struct due to the Foo field being a integer instead of a string:

{ "foo": "1" } // works
{ "foo": 1 } // doesn't

json.Unmarshal will blow up with the following error: json: cannot unmarshal number into Go struct field test.Foo of type string

See the reproduction: https://play.golang.org/p/4Qau3umaVm

Now in every other JSON library (in other languages) I have worked in so far, if the target field is a string and you get a integer the deserializer will usually just wrap the int in a string and be done with it. Can this be achieved in Go?

Since I can't really control how the data comes in I need to make json.Unmarshal unsensitive to this - the other solution would be to define Foo as interface{} which needlessly complicates my code with type assertions etc..

Any ideas on how to do this? I basically need the inverse of json:",string"

解决方案

To handle big structs you can use embedding.

Updated to not discard possibly previously set field values.

func (t *T) UnmarshalJSON(d []byte) error {
    type T2 T // create new type with same structure as T but without its method set!
    x := struct{
        T2 // embed
        Foo json.Number `json:"foo"`
    }{T2: T2(*t)} // don't forget this, if you do and 't' already has some fields set you would lose them

    if err := json.Unmarshal(d, &x); err != nil {
        return err
    }
    *t = T(x.T2)
    t.Foo = x.Foo.String()
    return nil
}

https://play.golang.org/p/BytXCeHMvt

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