json.Marshal(struct)返回``{}'' [英] json.Marshal(struct) returns "{}"

问题描述

type TestObject struct {
    kind string `json:"kind"`
    id   string `json:"id, omitempty"`
    name  string `json:"name"`
    email string `json:"email"`
}

func TestCreateSingleItemResponse(t *testing.T) {
    testObject := new(TestObject)
    testObject.kind = "TestObject"
    testObject.id = "f73h5jf8"
    testObject.name = "Yuri Gagarin"
    testObject.email = "[e-mail]"

    fmt.Println(testObject)

    b, err := json.Marshal(testObject)

    if err != nil {
        fmt.Println(err)
    }

    fmt.Println(string(b[:]))
}

以下是输出:

[ `go test -test.run="^TestCreateSingleItemResponse$"` | done: 2.195666095s ]
    {TestObject f73h5jf8 Yuri Gagarin [e-mail]}
    {}
    PASS

为什么JSON本质上是空的?

Why is the JSON essentially empty?

推荐答案

您需要导出通过大写字段名称中的第一个字母在TestObject中的字段.将kind更改为Kind，依此类推.

You need to export the fields in TestObject by capitalizing the first letter in the field name. Change kind to Kind and so on.

type TestObject struct {
 Kind string `json:"kind"`
 Id   string `json:"id,omitempty"`
 Name  string `json:"name"`
 Email string `json:"email"`
}

encoding/json包和类似的包会忽略未导出的字段.

The encoding/json package and similar packages ignore unexported fields.

遵循字段声明的`json:"..."`字符串是结构标签.在与JSON封送时，此结构中的标记设置该结构的字段名称.

The `json:"..."` strings that follow the field declarations are struct tags. The tags in this struct set the names of the struct's fields when marshaling to and from JSON.

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