Gorm How to get the additional info from the ManyToMany JoinTable?

Your Question

How to get the additional info from the ManyToMany JoinTable?

case: user - language (Many-to-Many)

like: ( there is a column named "Level" in JoinTable to describe somebody's language skill )

 User                    Language
┌────┬──────┐           ┌────┬─────────┐
│ ID │ Name │           │ ID │ Name    │
├────┼──────┤           ├────┼─────────┤
│  1 │ Amy  │           │  1 │ Chinese │
├────┼──────┤           ├────┼─────────┤
│  2 │ Bob  │           │  2 │ English │
├────┼──────┤           ├────┼─────────┤
│  3 │ Tom  │           │  3 │ French  │
└────┴──────┘           └────┴─────────┘

 UserLanguage
┌────┬────────┬────────────┬────────────────┐
│ ID │ UserID │ LanguageID │ Level          │
├────┼────────┼────────────┼────────────────┤
│  1 │    1   │      1     │ Newbie         │   // Amy can speak Chinese
├────┼────────┼────────────┼────────────────┤
│  2 │    1   │      2     │ Mother Tongue  │   // Amy can speak English
├────┼────────┼────────────┼────────────────┤
│  3 │    2   │      2     │ Native Speaker │   // Bob can speak English
└────┴────────┴────────────┴────────────────┘

My codes:

// Models
type User struct {
    ID int64 `json:"id" gorm:"primaryKey;autoIncrement"`
    Name string `json:"name"`
    Languages []Language `json:"languages" gorm:"many2many:user_language"`
}
func (User) TableName() string {
    return "user"
}

type Language struct {
    ID int64 `json:"id" gorm:"primaryKey;autoIncrement"`
    Name string `json:"name"`
    Level string `json:"level"`
}
func (Language) TableName() string {
    return "language"
}

type UserLanguage struct {
    ID int64 `json:"id" gorm:"primaryKey;autoIncrement"`
    UserId int64 `json:"user_id"`
    LanguageId int `json:"language_id"`
    Level string `json:"level"`
}
func (UserLanguage) TableName() string {
    return "user_language"
}

// Query
user := User{ID: 1}
DB.Preload("Languages").First(&user)
fmt.Println(user)

What I got:

{1 Amy [] [{1 Chinese } {2 English }]}

or in JSON format:

{
    "id":1,
    "name":"Amy",
    "languages":[
        {
            "id":1,
            "name":"Chinese",
            "level":""     // empty string
        },
        {
            "id":2,
            "name":"English",
            "level":""    // empty string
        }
    ]
}

The document you expected this should be explained

https://gorm.io/zh_CN/docs/many_to_many.html#%E8%87%AA%E5%AE%9A%E4%B9%89%E8%BF%9E%E6%8E%A5%E8%A1%A8

Expected answer

There are something in "level" ```json { "id":1, "name":"Amy", "languages":[ { "id":1, "name":"Chinese", "level":"Newbie" // Expected }, { "id":2, "name":"English", "level":"Mother Tongue" // Expected } ] }

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