Handling Custom BSON Marshaling

Question

I have a number of structs that require custom marshalling. When I was testing I was using JSON and the standard JSON marshaller. As it doesn\'t marshal unexported fields, I

Answer 1

Custom bson Marshalling/Unmarshalling works nearly the same way, you have to implement the Getter and Setter interfaces respectively

Something like this should work :

type Currency struct {
    value        decimal.Decimal //The actual value of the currency.
    currencyCode string          //The ISO currency code.
}

// GetBSON implements bson.Getter.
func (c Currency) GetBSON() (interface{}, error) {
    f := c.Value().Float64()
    return struct {
        Value        float64 `json:"value" bson:"value"`
        CurrencyCode string  `json:"currencyCode" bson:"currencyCode"`
    }{
        Value:        f,
        CurrencyCode: c.currencyCode,
    }, nil
}

// SetBSON implements bson.Setter.
func (c *Currency) SetBSON(raw bson.Raw) error {

    decoded := new(struct {
        Value        float64 `json:"value" bson:"value"`
        CurrencyCode string  `json:"currencyCode" bson:"currencyCode"`
    })

    bsonErr := raw.Unmarshal(decoded)

    if bsonErr == nil {
        c.value = decimal.NewFromFloat(decoded.Value)
        c.currencyCode = decoded.CurrencyCode
        return nil
    } else {
        return bsonErr
    }
}