CODEWITHSUNDEEP
sqlgomany-to-manygo-gorm
gmolveau
gmolveau

Reputation: 105

golang gorm many to many back reference

I have this models, many-to-many, and I'd like to get all the Gifs that matches a list of Tags.

type Tag struct {
    ID      uint    `gorm:"primary_key" json:"id,omitempty"`
    Name    string  `gorm:"not null;unique" json:"name,omitempty"`
}
type Gif struct {
    ID      uint    `gorm:"primary_key" json:"id,omitempty"`
    Url     string `gorm:"not null;unique" json:"url,omitempty"`
    Tags    []Tag `gorm:"many2many:gif_tags;" json:"tags,omitempty"`
}

I prepared a playground here.

If I have an array of Tags containing tag1 and tag2, I'd like to get gif1 and gif2 in &gifs.

I read the documentation many times and found only the opposite of my question, i.e. fetching the tags for a given gif.

Do I need to change my models?
Is it possible to set up two Associations fields in a many-to-many relation?

Upvotes: 1

Views: 2242

Answers (1)

gmolveau
gmolveau

Reputation: 105

So I found how to add back-reference.
I created two files in the same package containing the models, and added Associations with the same join-table for the many2many.

tag.go :

type Tag struct {
    ID   uint   `gorm:"primary_key" json:"id,omitempty"`
    Name string `gorm:"not null;unique" json:"name,omitempty"`
    Gifs []Gif  `gorm:"many2many:gif_tags;" json:"gifs,omitempty"`
}

and gif.go :

type Gif struct {
    ID   uint   `gorm:"primary_key" json:"id,omitempty"`
    Url  string `gorm:"not null;unique" json:"url,omitempty"`
    Tags []Tag  `gorm:"many2many:gif_tags;" json:"tags,omitempty"`
}

They need to be in separate files.

Now I can access easily all the gifs matching a Tag and vice-versa.

Upvotes: 2

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