如何不使用 Go 将空结构编组到 JSON 中? [英] How to not marshal an empty struct into JSON with Go?

问题描述

我有一个这样的结构:

type Result struct {
    Data       MyStruct  `json:"data,omitempty"`
    Status     string    `json:"status,omitempty"`
    Reason     string    `json:"reason,omitempty"`
}

但即使 MyStruct 的实例完全为空(即所有值都是默认值)，它也会被序列化为:

But even if the instance of MyStruct is entirely empty (meaning, all values are default), it's being serialized as:

"data":{}

我知道 encoding/json 文档指定空"字段是:

I know that the encoding/json docs specify that "empty" fields are:

false, 0, 任何 nil 指针或接口值，以及任何数组，切片、映射或长度为零的字符串

false, 0, any nil pointer or interface value, and any array, slice, map, or string of length zero

但不考虑具有所有空/默认值的结构.它的所有字段也都标有 omitempty，但这没有任何效果.

but with no consideration for a struct with all empty/default values. All of its fields are also tagged with omitempty, but this has no effect.

如何让 JSON 包不编组我的空结构字段?

How can I get the JSON package to not marshal my field that is an empty struct?

推荐答案

正如文档所说，任何 nil 指针".-- 使结构成为指针.指针有明显的空"值:nil.

As the docs say, "any nil pointer." -- make the struct a pointer. Pointers have obvious "empty" values: nil.

修复 - 使用结构指针字段定义类型:

Fix - define the type with a struct pointer field:

type Result struct {
    Data       *MyStruct `json:"data,omitempty"`
    Status     string    `json:"status,omitempty"`
    Reason     string    `json:"reason,omitempty"`
}

然后是这样的值:

result := Result{}

将编组为:

{}

说明:注意我们类型定义中的*MyStruct.JSON 序列化不关心它是否是一个指针——这是一个运行时细节.所以将结构体字段变成指针只对编译和运行时有影响).

Explanation: Notice the *MyStruct in our type definition. JSON serialization doesn't care whether it is a pointer or not -- that's a runtime detail. So making struct fields into pointers only has implications for compiling and runtime).

请注意，如果您确实将字段类型从 MyStruct 更改为 *MyStruct，您将需要指向结构值的指针来填充它，如下所示:

Just note that if you do change the field type from MyStruct to *MyStruct, you will need pointers to struct values to populate it, like so:

Data: &MyStruct{ /* values */ }

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