golang在for循环中追加问题

Question

问题：

append下面的内部Users()for 循环将users3x 中的最后一项添加到userRxs []*UserResolver

期待：

append应该将里面的每个项目添加users到userRxs []*UserResolver

// Users return all users from Db

func (r *RootResolver) Users() ([]*UserResolver, error) {

    var userRxs []*UserResolver

    users := r.Db.Users()

    for _, u := range users {

        log.Printf("userID: %s, username: %s, email: %s, password: %s", u.UserID, u.Username, u.Email, u.Password)

        userRxs = append(userRxs, &UserResolver{&u})

    }

    log.Printf("%v", userRxs)

    return userRxs, nil

}

在 for 循环内，log.Printf打印这个

userID: 0374402a-3dc4-48da-86c4-949905ccc26c, username: sunnysan, email: [e-mail], password: 12345678

userID: 53f21c4f-2cd8-4e67-b3e9-5ef344806230, username: sunnysan2, email: [e-mail], password: 12345678

userID: 0a47d3af-03dc-4050-a028-7a41599af497, username: sunnysan3, email: [e-mail], password: 12345678 

在 for 循环之后，log.Printf("%v", userRxs)打印这个

[

  User { 

    userID: 0a47d3af-03dc-4050-a028-7a41599af497, 

    username: sunnysan3, 

    email: [e-mail], 

    password: 12345678 

  }

  User { 

    userID: 0a47d3af-03dc-4050-a028-7a41599af497, 

    username: sunnysan3, 

    email: [e-mail], 

    password: 12345678 

  }

  User { 

    userID: 0a47d3af-03dc-4050-a028-7a41599af497, 

    username: sunnysan3, 

    email: [e-mail], 

    password: 12345678 

  }

]

这是整个文件以获取更多上下文

package main

import (

    "fmt"

    "log"

    graphql "github.com/graph-gophers/graphql-go"

)

/*

 *  User GQL type

        type User {

        userID: ID!

        username: String!

        email: String!

        password: String!

    }

*/

// User type should match the exact shape of the schema commented above

type User struct {

    UserID   graphql.ID

    Username string

    Email    string

    Password string

}

// RootResolver ingests Db to run queries (getters) against it

type RootResolver struct {

    *Db

}

Answer 1

范围变量在每次迭代时都会被覆盖，并且&u是相同的。所以你最终UserResolver会多次附加一个包含相同地址的地址。您需要使用该变量的本地副本。尝试这个：for _, u := range users {        u:=u  // Make a copy of the variable and redeclare it        userRxs = append(userRxs, &UserResolver{&u})    }