How to Store Embedded Structs in GORM within the Same Table as the Parent Struct?

Embedding Structs in GORM for Data Storage

In GORM, handling embedded structs can be a challenge when you want to store the nested struct within the same table as the parent struct. By default, GORM assumes embedded structs as separate entities and attempts to create a new table for them. However, you may prefer to include the embedded struct as an additional field within the parent struct's table.

Solution

One effective solution involves implementing the Scan() and Value() methods for a custom type that represents the embedded struct array. These methods allow GORM to serialize and deserialize the embedded struct to and from JSON, enabling seamless storage and retrieval.

For illustration, consider the following example:

<code class="go">type Child struct {
    Lat float64
    Lng float64
}

type ChildArray []Children

func (sla *ChildArray) Scan(src interface{}) error {
    return json.Unmarshal(src.([]byte), &sla)
}

func (sla ChildArray) Value() (driver.Value, error) {
    val, err := json.Marshal(sla)
    return string(val), err
}</code>

Here, the ChildArray custom type represents the embedded array of Child structs. It implements the Scan() and Value() methods to handle JSON serialization and deserialization.

To embed and store the ChildArray in the Parent struct, you can define the model as follows:

<code class="go">type Parent struct {
    *gorm.Model
    Childrens ChildArray `gorm:"column:childrens;type:longtext"`
}</code>

With this configuration, GORM recognizes the Childrens field as a custom type and automatically serializes and deserializes the embedded Child structs to and from JSON when interacting with the database.

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