在 Go App Engine 中实现一对多关系

type Vote struct {
    User       string
    Score      int
    CommentKey *datastore.Key
}

type Comment struct {
    Author  string
    Content string
    Date    datastore.Time
}

package main

import (
    "context"
    "fmt"
    "log"
    "os"

    "cloud.google.com/go/datastore"
)

type Comment struct {
    Author  string
    Content string
}

type Vote struct {
    User       string
    Score      int
    CommentKey *datastore.Key
}

func main() {
    // Replace with your Google Cloud project ID
    projectID := "your-project-id"

    // Create a new datastore client.
    ctx := context.Background()
    client, err := datastore.NewClient(ctx, projectID)
    if err != nil {
        log.Fatalf("Failed to create client: %v", err)
    }
    defer client.Close()

    // Create a new comment.
    comment := Comment{
        Author:  "John Doe",
        Content: "This is a great post!",
    }

    // Save the comment to the datastore.
    commentKey := datastore.NameKey("Comment", "unique-comment-id", nil)
    commentKey, err = client.Put(ctx, commentKey, &comment)
    if err != nil {
        log.Fatalf("Failed to save comment: %v", err)
    }

    // Create some votes for the comment.
    votes := []Vote{
        {User: "Alice", Score: 5, CommentKey: commentKey},
        {User: "Bob", Score: 4, CommentKey: commentKey},
    }

    // Save the votes to the datastore.
    for _, vote := range votes {
        voteKey := datastore.NewIncompleteKey(ctx, "Vote", nil)
        _, err = client.Put(ctx, voteKey, &vote)
        if err != nil {
            log.Fatalf("Failed to save vote: %v", err)
        }
    }

    // Query for all votes for the comment.
    query := datastore.NewQuery("Vote").Filter("CommentKey =", commentKey)
    var retrievedVotes []Vote
    _, err = client.GetAll(ctx, query, &retrievedVotes)
    if err != nil {
        log.Fatalf("Failed to retrieve votes: %v", err)
    }

    // Print the retrieved votes.
    fmt.Println("Votes for comment:")
    for _, vote := range retrievedVotes {
        fmt.Printf("  User: %s, Score: %d\n", vote.User, vote.Score)
    }
}