How do I embed a struct within another struct in GORM and store it as a field in the main table?

Embedding Structs with GORM

In GORM, when embedding a struct within another, GORM may create a separate table for the embedded struct. However, if you wish to store the embedded struct as an additional field within the main table, the following approach can be utilized:

Solution:

1. Define an embedded struct:

<code class="go">type A struct {
    Point *GeoPoint
}

type GeoPoint struct {
    Lat float64
    Lon float64
}</code>

2. Implement the sql.Scanner and driver.Valuer interfaces for the embedded struct:

<code class="go">func (gp *GeoPoint) Scan(src interface{}) error {

    // Convert the `src` value to a byte array.
    b, ok := src.([]byte)
    if !ok {
        return fmt.Errorf("could not convert to byte array")
    }

    // Unmarshal the byte array into the `GeoPoint` struct.
    if err := json.Unmarshal(b, gp); err != nil {
        return fmt.Errorf("could not unmarshal JSON: %v", err)
    }

    return nil
}

func (gp GeoPoint) Value() (driver.Value, error) {

    // Marshal the `GeoPoint` struct into a byte array.
    b, err := json.Marshal(gp)
    if err != nil {
        return nil, fmt.Errorf("could not marshal JSON: %v", err)
    }

    return string(b), nil
}</code>

3. Update the GORM model to use the embedded struct with the gorm:"column" and gorm:"type" tags:

<code class="go">type A struct {
    gorm.Model
    Point *GeoPoint `gorm:"column:point;type:json"`
}</code>

By implementing the Scan and Value methods, GORM can convert the embedded struct to and from a JSON format. The gorm:"column" and gorm:"type" tags specify the column name and data type for the embedded struct within the main table.

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