英文:
Golang Gorm not retrieving data from associated table
问题
我正在使用Gorm和MySQL开发一个Gin应用程序。为了在Gorm模型中定义“属于”关系，你需要按照以下步骤进行操作（示例取自Gorm文档）：
// `User`属于`Company`，`CompanyID`是外键type User struct {gorm.ModelName stringCompanyID intCompany Company}type Company struct {ID intName string}
这是我在我的模型中所做的：
type Record struct {Barcode string `json:"barcode" gorm:"size:48;unique;not null" sql:"index"`Name string `json:"name" gorm:"size:160;unique;not null"`ArtistID uint `json:"artist_id"`Artist Artist `gorm:"foreignKey:ArtistID;references:ID"`CategoryID uint `json:"category_id"`Category Category `gorm:"foreignKey:CategoryID;references:ID"`NumOfRecords int `json:"num_of_records" gorm:"not null"`OriginalReleaseDate *utils.Date `json:"original_release_date" gorm:"default:null;type:date"`ReissueReleaseDate *utils.Date `json:"reissue_release_date" gorm:"default:null;type:date"`SideColor *string `json:"side_color" gorm:"default:null"`BarcodeInRecord *bool `json:"barcode_in_record" gorm:"default:true"`gorm.Model}
type Category struct {Name string `json:"name" gorm:"size:60;unique;not null"`Description string `json:"description" gorm:"size:120"`Parent uint `json:"parent" gorm:"default:null"`Active bool `json:"active" gorm:"default:true"`gorm.Model}
type Artist struct {Name string `json:"name" gorm:"size:120;unique;not null"`Type string `json:"type" gorm:"default:null"`CountryOfOrigin string `json:"countryOfOrigin" gorm:"default:null"`gorm.Model}
然而，在获取数据时，这两个关联对象没有被填充：
{"data": {"barcode": "1231231231231292","name": "ABCD 12342","artist_id": 2,"Artist": {"name": "","type": "","countryOfOrigin": "","ID": 0,"CreatedAt": "0001-01-01T00:00:00Z","UpdatedAt": "0001-01-01T00:00:00Z","DeletedAt": null},"category_id": 9,"Category": {"name": "","description": "","parent": 0,"active": false,"ID": 0,"CreatedAt": "0001-01-01T00:00:00Z","UpdatedAt": "0001-01-01T00:00:00Z","DeletedAt": null},"num_of_records": 2,"original_release_date": "1965-02-24","reissue_release_date": null,"side_color": null,"barcode_in_record": null,"ID": 1,"CreatedAt": "2022-04-25T12:53:32.275578-04:00","UpdatedAt": "2022-04-25T12:53:32.275578-04:00","DeletedAt": null}}
有什么想法是怎么回事吗？
英文:
I'm working on a Gin app using Gorm with MySQL. In order to define a belongs to relationship in a Gorm Model, you have to do the following (example taken from Gorm docs):
// `User` belongs to `Company`, `CompanyID` is the foreign keytype User struct {gorm.ModelName stringCompanyID intCompany Company}type Company struct {ID intName string}
That's what I did with my models:
type Record struct {Barcode string `json:"barcode" gorm:"size:48;unique;not null" sql:"index"`Name string `json:"name" gorm:"size:160;unique;not null"`ArtistID uint `json:"artist_id"`Artist Artist `gorm:"foreignKey:ArtistID;references:ID"`CategoryID uint `json:"category_id"`Category Category `gorm:"foreignKey:CategoryID;references:ID"`NumOfRecords int `json:"num_of_records" gorm:"not null"`OriginalReleaseDate *utils.Date `json:"original_release_date" gorm:"default:null;type:date"`ReissueReleaseDate *utils.Date `json:"reissue_release_date" gorm:"default:null;type:date"`SideColor *string `json:"side_color" gorm:"default:null"`BarcodeInRecord *bool `json:"barcode_in_record" gorm:"default=true"`gorm.Model}
type Category struct {Name string `json:"name" gorm:"size:60;unique;not null"`Description string `json:"description" gorm:"size:120"`Parent uint `json:"parent" gorm:"default:null"`Active bool `json:"active" gorm:"default:true"`gorm.Model}
type Artist struct {Name string `json:"name" gorm:"size:120;unique;not null"`Type string `json:"type" gorm:"default:null"`CountryOfOrigin string `json:"countryOfOrigin" gorm:"default:null"`gorm.Model}
yet when getting data back, those two associations are not being populated:
{"data": {"barcode": "1231231231231292","name": "ABCD 12342","artist_id": 2,"Artist": {"name": "","type": "","countryOfOrigin": "","ID": 0,"CreatedAt": "0001-01-01T00:00:00Z","UpdatedAt": "0001-01-01T00:00:00Z","DeletedAt": null},"category_id": 9,"Category": {"name": "","description": "","parent": 0,"active": false,"ID": 0,"CreatedAt": "0001-01-01T00:00:00Z","UpdatedAt": "0001-01-01T00:00:00Z","DeletedAt": null},"num_of_records": 2,"original_release_date": "1965-02-24","reissue_release_date": null,"side_color": null,"barcode_in_record": null,"ID": 1,"CreatedAt": "2022-04-25T12:53:32.275578-04:00","UpdatedAt": "2022-04-25T12:53:32.275578-04:00","DeletedAt": null}}
any idea what's going on there?
答案1
得分: 2
保存数据到数据库的代码是怎样的？
我猜你可能需要使用FullSaveAssociations，类似这样：
DB().Session(&gorm.Session{FullSaveAssociations: true}).Save(&d)
要获取数据，你需要使用Preloads。
DB().Preload("Artist").Preload("Category").First(&d)
你还可以使用
.Preload(clause.Associations)
来加载它们。你可以与其他Preloads一起使用，以深入加载。
https://gorm.io/docs/preload.html#content-inner
英文:
What does the code look like that is saving the data to the db?
I'm guessing that you probably need to use FullSaveAssociations
something like this:
DB().Session(&gorm.Session{FullSaveAssociations: true}).Save(&d)
To get the data back, you need to use Preloads.
DB().Preload("Artist").Preload("Category").First(&d)
you can also use
.Preload(clause.Associations)
to load them all. You can use this with other Preloads to go deeper.
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