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Polymorphism Polymorphism Association GORM supports polymorphism association for has one and has many, it will save owned entity’s table name into polymorphic type’s field, primary key value into the polymorphic field
By default polymorphic: will prefix the column type and column id with . The value will be the table name pluralized.
type Dog struct {
ID int
Name string
Toys []Toy gorm:"polymorphic:Owner;"
}
type Toy struct { ID int Name string OwnerID int OwnerType string }
db.Create(&Dog{Name: "dog1", Toys: []Toy{{Name: "toy1"}, {Name: "toy2"}}})
// INSERT INTO dogs (name) VALUES ("dog1")
// INSERT INTO toys (name,owner_id,owner_type) VALUES ("toy1",1,"dogs"), ("toy2",1,"dogs")
You can specify polymorphism properties separately using the following GORM tags:
polymorphicType: Specifies the column type.
polymorphicId: Specifies the column ID.
polymorphicValue: Specifies the value of the type.
type Dog struct {
ID int
Name string
Toys []Toy gorm:"polymorphicType:Kind;polymorphicId:OwnerID;polymorphicValue:master"
}
type Toy struct { ID int Name string OwnerID int Kind string }
db.Create(&Dog{Name: "dog1", Toys: []Toy{{Name: "toy1"}, {Name: "toy2"}}})
// INSERT INTO dogs (name) VALUES ("dog1")
// INSERT INTO toys (name,owner_id,kind) VALUES ("toy1",1,"master"), ("toy2",1,"master")
In these examples, we’ve used a has-many relationship, but the same principles apply to has-one relationships.