使用golang向DynamoDB封送/解组“枚举”

Question

I have the following PartnerType "enum" struct in go:

// PartnerType enum
type PartnerType int

const (
    // PartnerTypeUnknown should never happen
    PartnerTypeUnknown PartnerType = iota

    // PartnerTypeTest test
    PartnerTypeTest
)

func (t PartnerType) String() string {
    names := [...]string{
        "UNKNOWN",
        "TEST"}

    if t < PartnerTypeUnknown || t > PartnerTypeTest {
        return names[0]
    }
    return names[t]
}

// MarshalJSON for enum
func (t PartnerType) MarshalJSON() ([]byte, error) {
    s := t.String()
    return json.Marshal(s)
}

// UnmarshalJSON for enum
func (t *PartnerType) UnmarshalJSON(b []byte) error {
    *t = PartnerTypeUnknown
    return nil
}

// MarshalText implements the text marshaller method
func (t *PartnerType) MarshalText() ([]byte, error) {
    return []byte(t.String()), nil
}

// UnmarshalText implements the text unmarshaller method
func (t *PartnerType) UnmarshalText(text []byte) error {
    *t = PartnerTypeUnknown
    return nil
}

// Partner entity
type Partner struct {
    ID   string `dynamodbav:"PK,omitempty"`
    Foo string `dynamodbav:"SK,omitempty"`
    PartnerType              PartnerType    `dynamodbav:",omitempty,string"`
}

When doing a dynamodbattribute.MarshalMap() I'd like my PartnerType to be stored as a string. The dynamodbav struct tag allows you to store an int as a string (dynamodbav:",omitempty,string") however it is not calling my defined .String() or Marshal/Unmarshal implementations.

Said another way, it stores PartnerTypeTest as "1" not "TEST".

How can this be done?

Answer 1

For dynamodb you can implement your marshaler/unmarshaler for enums

Try the following:

// MarshalDynamoDBAttributeValue for ddb
func (t PartnerType) MarshalDynamoDBAttributeValue(av *dynamodb.AttributeValue) error {
    s := t.String()
    av.S = &s
    return nil
}

// UnmarshalDynamoDBAttributeValue implements the Unmarshaler interface
func (t *PartnerType) UnmarshalDynamoDBAttributeValue(av *dynamodb.AttributeValue) error {
    // val := aws.StringValue(av.S)

    *t = PartnerTypeUnknown
    return nil
}