使用Gorm时无法检索Has Many关联的问题

huangapple
go评论126阅读模式
英文:

Trouble retrieving Has Many using Gorm

问题

当我尝试从播客中获取剧集时，我得到了invalid association []的错误。不确定我做错了什么。

  1. package main
  3. import (
  4. 	"log"
  6. 	"github.com/jinzhu/gorm"
  7. 	_ "github.com/mattn/go-sqlite3"
  8. )
  10. type Podcast struct {
  11. 	Id       int
  12. 	Title    string
  13. 	RssUrl   string `sql:"unique_index"`
  14. 	Url      string
  15. 	Episodes []Episode
  16. }
  18. type Episode struct {
  19. 	Id         int
  20. 	PodcastID  int `sql:"index"`
  21. 	Title      string
  22. 	Url        string `sql:"unique_index"`
  23. 	Downloaded bool
  24. }
  26. func main() {
  27. 	db, err := gorm.Open("sqlite3", "gorm.db")
  28. 	if err != nil {
  29. 		log.Fatal(err)
  30. 	}
  31. 	db.LogMode(true)
  33. 	db.CreateTable(&Podcast{})
  34. 	db.CreateTable(&Episode{})
  36. 	podcast := Podcast{
  37. 		Title:    "My Podcast",
  38. 		RssUrl:   "http://example.com/feed/",
  39. 		Url:      "http://www.example.com",
  40. 		Episodes: []Episode{{Title: "Episode One Point Oh!", Url: "http://www.example.com/one-point-oh", Downloaded: false}},
  41. 	}
  43. 	var episodes []Episode
  44. 	db.Model(&podcast).Related(&episodes)
  45. }
英文:

When I try to get episodes back from a podcast I get invalid association []. Not sure what I'm doing wrong.

  1. package main
  3. import (
  4. 	"log"
  6. 	"github.com/jinzhu/gorm"
  7. 	_ "github.com/mattn/go-sqlite3"
  8. )
  10. type Podcast struct {
  11. 	Id       int
  12. 	Title    string
  13. 	RssUrl   string `sql:"unique_index"`
  14. 	Url      string
  15. 	Episodes []Episode
  16. }
  18. type Episode struct {
  19. 	Id         int
  20. 	PodcastID  int `sql:"index"`
  21. 	Title      string
  22. 	Url        string `sql:"unique_index"`
  23. 	Downloaded bool
  24. }
  26. func main() {
  27. 	db, err := gorm.Open("sqlite3", "gorm.db")
  28. 	if err != nil {
  29. 		log.Fatal(err)
  30. 	}
  31. 	db.LogMode(true)
  33. 	db.CreateTable(&Podcast{})
  34. 	db.CreateTable(&Episode{})
  35. 	
  36. 	podcast := Podcast{
  37. 	  Title:    "My Podcast",
  38. 	  RssUrl:   "http://example.com/feed/",
  39. 	  Url:      "http://www.example.com",
  40. 	  Episodes: []Episode{{Title: "Episode One Point Oh!", Url: "http://www.example.com/one-point-oh", Downloaded: false}},
  41. 	}
  43. 	var episodes []Episode
  44. 	db.Model(&podcast).Related(&episodes)
  45. }

答案1

得分: 1

你正在使用的GO和GORM版本是哪个？我在我的机器上尝试了一下，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，因为您没有创建podcast变量，所以podcast_id为0，所以查询没有太多意义。

为了创建podcast，只需添加以下代码：

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

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

log.Print(episodes)

英文:

Which version of GO and GORM are you using? I've tried on my machine and this is the log:

  1. [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"))
  2. [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")) 
  3. [2015-06-17 19:02:11]  [1.25ms]  SELECT  * FROM "episodes"  WHERE ("podcast_id" = '0')

Please note that because you didn't create the podcast variable, the podcast_id is 0 so the query does not make so much sense.

In order to create the podcast, simply add this code

  1. db.NewRecord(podcast)
  2. db.Create(&podcast)
  4. var episodes []Episode
  5. db.Model(&podcast).Related(&episodes)
  7. log.Print(episodes)

huangapple
  • 本文由 发表于 2015年6月18日 00:20:40
  • 转载请务必保留本文链接：https://go.coder-hub.com/30897123.html
  • go
  • go-gorm
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