问题
I have a Go struct which contains a slice of strings which I'd like to save as a jsonB object in Postgres with GORM.
I've come accross a solution which requires to use the GORM specific type (postgres.Jsonb) which I'd like to avoid.
When I try to run the AutoMigrate with a slice in my model, it panics and won't start although when I wrap this slice in a struct (which I'm okay doing) it will run without error but won't create the column in postgres.
type User struct {
gorm.Model
Data []string `sql:"type:"jsonb"; json:"data"`
} //Panics
type User struct {
gorm.Model
Data struct {
NestedData []string
} `sql:"type:"jsonb"; json:"data"`
} //Doesn't crash but doesn't create my column
Has anyone been able to manipulate jsonb with GORM without using the postgres.Jsonb type in models ?
回答1:
Maybe:
type DataJSONB []string
func (dj DataJSONB) Value() (driver.Value, error) {
return json.Marshal(dj)
}
func (dj *DataJSONB) Scan(value interface{}) error {
b, ok := value.([]byte)
if !ok {
return fmt.Errorf("[]byte assertion failed")
}
return json.Unmarshal(b, dj)
}
// Your bit
type User struct {
gorm.Model
Data DataJSONB `sql:"type:"jsonb"; json:"data"`
}
回答2:
Define a new type:
type Data map[string]interface{}
And implement the Valuer
and Scanner
interfaces onto them, which allows the field to be converted to a value for the database, and scanned back into the field, respectively:
// Value converts into []byte
func (d Data) Value() (driver.Value, error) {
j, err := json.Marshal(d)
return j, err
}
// Scan puts the []byte back into Data
func (d *Data) Scan(src interface{}) error {
source, ok := src.([]byte)
if !ok {
return errors.New("Type assertion .([]byte) failed.")
}
var i interface{}
if err := json.Unmarshal(source, &i); err != nil {
return err
}
*d, ok = i.(map[string]interface{})
if !ok {
return errors.New("Type assertion .(map[string]interface{}) failed.")
}
return nil
}
Then you can define your field in your model like this:
type User struct {
gorm.Model
Data Data `type: jsonb not null default '{}'::jsonb`
}
Using the underlying map[string]interface{}
type is nice too, as you can Unmarshal
/Marshal
any JSON to/from it.
来源:https://stackoverflow.com/questions/60092840/string-to-jsonb-with-gorm-and-postgres