在golang中嵌入结构会产生错误“未知字段”。 [英] Embedding structs in golang gives error "unknown field"

问题描述

我在用户程序包中有一个结构，名为 account

i have a struct in user package called account

type Account struct {
    Tp          string `json:"type"bson:"type"`
    AccountId   string  `json:"account_id"bson:"account_id"`
    Credentials map[string]interface{} `json:"credentials,omitempty"bson:"credentials,omitempty"`
    ProfilePicture string `json:"profile_picture,omitempty"`
    Username string `json:"username"bson:"username"`
    AccessToken map[string]interface{}`bson:"access_token,omitempty"`
}

和用户/帐户 im尝试将此帐户结构嵌入另一个结构中

and in user/accounts im trying to embed this account struct into another struct

type returnAccount struct {
    user.Account
    AccessToken string `json:"access_token,omitempty"`
}

用户包在尝试之前已正确导入嵌入我正在成功使用它

user package is properly imported before trying to embed i was using it successfully

最终在循环中我得到了输入用户帐户并制作 returnAccount 的地图，然后从我的函数
返回，这是我的函数

finaly in a loop i am getting user accounts and making a map of returnAccount and returning from my function here is my function

func getAccounts(usr *user.AuthenticatedUser, id ...string) (accounts map[string]returnAccount) {
    accounts = make(map[string]returnAccount)
    if len(id) > 0 {
        for _, v := range id {
            for _, acnt := range usr.Accounts {
                if acnt.AccountId == v {
                    accounts[acnt.AccountId] = returnAccount{
                        Tp:       acnt.Tp,
                        AccountId:acnt.AccountId,
                    }
                }
            }
        }
        return
    }
    for _, v := range usr.Accounts {
        accounts[v.AccountId] = returnAccount{
            Tp:       v.Tp,
            AccountId:v.AccountId,
            Username: v.Username,

        }

    }
    return
}

但是此代码不会在此处编译，错误消息

However this code wont compile here is the error message

# sgin/api/user/accounts
api/user/accounts/getaccounts.go:16: unknown returnAccount field 'Tp' in struct literal
api/user/accounts/getaccounts.go:17: unknown returnAccount field 'AccountId' in struct literal
api/user/accounts/getaccounts.go:26: unknown returnAccount field 'Tp' in struct literal
api/user/accounts/getaccounts.go:27: unknown returnAccount field 'AccountId' in struct literal
api/user/accounts/getaccounts.go:28: unknown returnAccount field 'Username' in struct literal

$ b中的未知returnAccount字段'Username'
$ b

一切似乎都非常简单明了，我无法弄清楚为什么会出现此错误，我需要达到Account结构的所有成员都已导出

everything seems pretty straightforward and simple i cannot figure out why i get this error all members i need to reach of the Account struct are exported

我需要此字段的原因是我想通过api发送访问令牌给客户端，而不是秘密，并且我想降低缩进级别

The reason why i need this field is i want to send access token to clients through api but not the secret and also i want to reduce the indention level

推荐答案

您正在尝试初始化提升字段，这是复合文字无法实现的。来自查看规范：

You are trying to initialize promoted fields which is not possible by composite literals. From Go spec:

如果 xf 是表示该字段或方法f的合法选择器，则结构x中匿名字段的字段或方法f被称为升级。

A field or method f of an anonymous field in a struct x is called promoted if x.f is a legal selector that denotes that field or method f.

已升级字段的作用类似于结构的普通字段，只是它们不能用作
结构的组合文字中的字段名称。

Promoted fields act like ordinary fields of a struct except that they cannot be used as field names in composite literals of the struct.

但是您可以使用点符号来访问它们：

But you can access them using dot notation:

ra:= returnAccount{}
ra.Tp = acnt.Tp

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