Gorm插入多对多不添加到连接表

Question

I have two tables: Meeting and Participant . A meeting can have multiple participants while a participant can attend multiple meetings. This many2many relationship is structured in gorm as follow:

type Meeting struct {
    Id          uint   `json:"id" gorm:"primary_key"`
    MeetingName string `json:"meetingName" binding:"required"`
    Participants   []Participant  `json:"participants" gorm:"many2many:meeting_participants" binding:"required"`
}

type Participant struct {
    Id             uint           `json:"id" gorm:"primary_key"`
    Name           string         `json:"name" validate:"required"`
    Meetings       []Meeting      `json:"meetings" gorm:"many2many:meeting_participants"`
}

The issue is that when I add a new participant, gorm is not adding to the join table (meeting_participants). A new participant is added but the join table has no new record. The script to add participant is as follow:

func InsertParticipant(c *gin.Context) (string, error) {
    input, err := checkParticipantInput(c)
    if err != nil {
        return "", err
    }

    newParticipant := DB.Create(&input)
    DB.Save(&input)

    return input.Id, newParticipant.Error
}

func checkParticipantInput(c *gin.Context) (Participant, error) {
    var input Participant
    err := c.ShouldBindJSON(&input)
    if err != nil {
        return Participant{}, err
    }

    return input, err
}

Json input:

{
    "name":"testParticipant",
    "meetings": [{"id": 40}]
}

Any idea what went wrong? Thanks in advance.

Answer 1

I have two tables: Meeting and Participant . A meeting can have multiple participants while a participant can attend multiple meetings. This many2many relationship is structured in gorm as follow:

type Meeting struct {
    Id          uint   `json:"id" gorm:"primary_key"`
    MeetingName string `json:"meetingName" binding:"required"`
    Participants   []Participant  `json:"participants" gorm:"many2many:meeting_participants" binding:"required"`
}

type Participant struct {
    Id             uint           `json:"id" gorm:"primary_key"`
    Name           string         `json:"name" validate:"required"`
    Meetings       []Meeting      `json:"meetings" gorm:"many2many:meeting_participants"`
}

The issue is that when I add a new participant, gorm is not adding to the join table (meeting_participants). A new participant is added but the join table has no new record. The script to add participant is as follow:

func InsertParticipant(c *gin.Context) (string, error) {
    input, err := checkParticipantInput(c)
    if err != nil {
        return "", err
    }

    newParticipant := DB.Create(&input)
    DB.Save(&input)

    return input.Id, newParticipant.Error
}

func checkParticipantInput(c *gin.Context) (Participant, error) {
    var input Participant
    err := c.ShouldBindJSON(&input)
    if err != nil {
        return Participant{}, err
    }

    return input, err
}

Any idea what went wrong? Thanks in advance.

Answer 2

Not so sure why but I restarted my server and it works. Perhaps something to do with automigrate not working when the server hot reloads.