go - 使用 Gorm 检索有很多问题

Question

当我尝试从播客中取回剧集时，我得到invalid association []. 不知道我做错了什么。

package main

import (
    "log"

    "github.com/jinzhu/gorm"
    _ "github.com/mattn/go-sqlite3"
)

type Podcast struct {
    Id       int
    Title    string
    RssUrl   string `sql:"unique_index"`
    Url      string
    Episodes []Episode
}

type Episode struct {
    Id         int
    PodcastID  int `sql:"index"`
    Title      string
    Url        string `sql:"unique_index"`
    Downloaded bool
}

func main() {
    db, err := gorm.Open("sqlite3", "gorm.db")
    if err != nil {
        log.Fatal(err)
    }
    db.LogMode(true)

    db.CreateTable(&Podcast{})
    db.CreateTable(&Episode{})

    podcast := Podcast{
      Title:    "My Podcast",
      RssUrl:   "http://example.com/feed/",
      Url:      "http://www.example.com",
      Episodes: []Episode{{Title: "Episode One Point Oh!", Url: "http://www.example.com/one-point-oh", Downloaded: false}},
    }

    var episodes []Episode
    db.Model(&podcast).Related(&episodes)
}

Answer 1

您使用的是哪个版本的 GO 和 GORM？我在我的机器上试过，这是日志：

[2015-06-17 19:02:11]  [12.00ms]  CREATE TABLE "podcasts" ("id" integer,"title" varchar(255),"rss_url" varchar(255),"url" varchar(255) , PRIMARY KEY ("id"))
[2015-06-17 19:02:11]  [1.26ms]  CREATE TABLE "episodes" ("id" integer,"podcast_id" integer,"title" varchar(255),"url" varchar(255),"downloaded" bool , PRIMARY KEY ("id")) 
[2015-06-17 19:02:11]  [1.25ms]  SELECT  * FROM "episodes"  WHERE ("podcast_id" = '0')

请注意，由于您没有创建 podcast 变量，因此 podcast_id 为 0，因此查询没有多大意义。

为了创建播客，只需添加此代码

db.NewRecord(podcast)
db.Create(&podcast)

var episodes []Episode
db.Model(&podcast).Related(&episodes)

log.Print(episodes)