Golang 中奇怪的类型定义语法(名称，然后类型，然后是字符串字面量) [英] Strange type definition syntax in Golang (name, then type, then string literal)

问题描述

我一直在试图找出如何使用 mgo(用于 Go 的 MongoDB 驱动程序)，但我遇到了这个结构声明:

I've been trying to find out how to use mgo (MongoDB driver for Go) and I came across this struct declaration:

type Something struct {
    Id bson.ObjectId "_id,omitempty"
    Name string
}

我不太明白第一个元素 (Id) 的语法.我知道它被声明为 bson.ObjectId 类型，但是字符串文字在那里做什么?

I don't quite understand the syntax of the first element (Id). I understand that it's being declared as type bson.ObjectId, but what is the string literal doing there?

我的问题不是关于 mgo 驱动程序的功能，
但是关于这个奇怪的 <类型> 语法.

My question is not about the mgo driver functionality,
but about this strange <name> <type> <string_literal> syntax.

我在 Go 规范上找不到任何内容，我也不知道如何在谷歌上搜索.

I couldn't find anything on the Go specs, and I don't know how to google this either.

推荐答案

在结构类型语言规范的a>部分:

It's explained in the Struct types section of the language specification:

一个字段声明可以跟一个可选的字符串文字标签，它成为对应字段声明中所有字段的属性.标签通过反射接口，否则会被忽略.

A field declaration may be followed by an optional string literal tag, which becomes an attribute for all the fields in the corresponding field declaration. The tags are made visible through a reflection interface but are otherwise ignored.

// A struct corresponding to the TimeStamp protocol buffer.
// The tag strings define the protocol buffer field numbers.
struct {
    microsec  uint64 "field 1"
    serverIP6 uint64 "field 2"
    process   string "field 3"
}

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