如何row.Scan（）int32进入Golang gRPC protobuf枚举字段？

Question

// agent.proto

message Agent {
    Permission permission = 1;
    google.protobuf.Timestamp born_time = 2;

    message Permission {
        Type type = 1;

        enum Type {
            KILLNONE = 0;
            KILLALL = 1;
            DANCE = 2;
        }
   }
}

Then scanning SQL row into agent protobuf struct:

// main.go

var a proto.Agent

.....

... row.Scan(&a.Permission.Type,...)

That permission type is stored as simple MariaDB INT() value = 0 for default type. So, i can't scan it directly. So i made temp struct where Type int32 and scaned row into that temp struct after what tried to map temp struct fields to protobuf struct, but with no luck. Similar issues i had when want to scan MariaDB string values into []byte type fields but i solved that with my temp struct []byte(tmp.UUID).

What is common patterns to scan database ROW (single row) into protubuf message when non-standard protobuf field types are used?

EDIT: Does there should be some additional 0 value handling?

Answer 1

I usually work with Go types within the business domain, and use adapters to convert to/from the protobuf type.

// Role represents a set of permissions
type Role struct {
    KILLNONE = iota
    KILLALL
    DANCE
}

// Permission represents a set of agent permissions
type Permission struct {
    Role Role
}

// ToProto converts a Permission Go type to a protobuf Permission
func (p Permission) ToProto() (proto.Permission) {
    pb := proto.Permission{}
    // assign p's properties to proto's respective properties
    // with necessary type conversions.
    ...
    return pb
}

The protobuf examples usually show working with the protobuf types directly, but it seems like adapters are more common in the field.