Inserting and selecting PostGIS Geometry with Gorm

Question

I\'ve been trying to find a way to insert and retrieve geometric types using Golang, and specifically the library gorm. I\'m also attempting to use the library orb that defines

Answer 1

Another solution, which I ended up using was with go-geos, as I discovered I needed to use the GEOS C library. With that, I am able to convert the struct into WKT for inserting (as postgis accepts it as regular text) and convert from WKB when scanning.

type Geometry4326 *geos.Geometry

// Value converts the given Geometry4326 struct into WKT such that it can be stored in a 
// database. Implements Valuer interface for use with database operations.
func (g Geometry4326) Value() (driver.Value, error) {

    str, err := g.ToWKT()
    if err != nil {
        return nil, err
    }

    return "SRID=4326;" + str, nil
}

// Scan converts the hexadecimal representation of geometry into the given Geometry4326 
// struct. Implements Scanner interface for use with database operations.
func (g *Geometry4326) Scan(value interface{}) error {

    bytes, ok := value.([]byte)
    if !ok {
        return errors.New("cannot convert database value to geometry")
    }

    str := string(bytes)

    geom, err := geos.FromHex(str)
    if err != nil {
        return errors.Wrap(err, "cannot get geometry from hex")
    }

    geometry := Geometry4326(geom)
    *g = geometry

    return nil
}

This solution might not be ideal for everyone as not everyone needs to use the GEOS C library, which can be a pain to get working on windows. I'm sure though that the same thing can be accomplished using different libraries.

I additionally implemented UnmarshalJSON() and MarshalJSON() on the struct so that it can automatically Marshal/Unmarshal GeoJSON, and then save/get from the database seamlessly. I accomplished this using geojson-go to convert GeoJSON to/from a struct, and then geojson-geos-go to convert said struct into the go-geos struct I was using. A little convoluted, yes, but it works.