关于golang中的结构体

Question

这些天看aws的golang sdk中结构体中有

_ struct{} `type:"structure"`

不知道 下划线 _ 是什么意思，注意不是tag

// Please also see https://docs.aws.amazon.com/goto/WebAPI/s3-2006-03-01/MultipartUpload
type MultipartUpload struct {
    _ struct{} `type:"structure"`

    // Date and time at which the multipart upload was initiated.
    Initiated *time.Time `type:"timestamp" timestampFormat:"iso8601"`

    // Identifies who initiated the multipart upload.
    Initiator *Initiator `type:"structure"`

    // Key of the object for which the multipart upload was initiated.
    Key *string `min:"1" type:"string"`

    Owner *Owner `type:"structure"`

    // The class of storage used to store the object.
    StorageClass *string `type:"string" enum:"StorageClass"`

    // Upload ID that identifies the multipart upload.
    UploadId *string `type:"string"`
}

Answer 1

这个叫struct tag

Go offers struct tags which are discoverable via reflection. These enjoy a wide range of use in the standard library in the JSON/XML and other encoding packages.

The community welcomed them and has built ORMs, further encodings, flag parsers and much more around them since, especially for these tasks, single-sourcing is beneficial for data structures.

Answer 2

相当于给struct中的字段添加了tag属性，可以通过reflect包来获取struct中字段的属性