Name Mappers

Name Mappers

Pie supports multiple name mapping strategies to adapt to different Go struct field and MongoDB field naming conventions.

Default Mapping

By default, Pie converts Go struct field names to camelCase as MongoDB field names.

type User struct {
    ID        bson.ObjectID `bson:"_id,omitempty"`
    FirstName string        `bson:"first_name"` // Explicit specification
    LastName  string        `bson:"last_name"`  // Explicit specification
    Email     string        // Default mapping to "email"
    CreatedAt time.Time     // Default mapping to "createdAt"
}

Snake Case Mapping

If you want to convert Go struct field names to snake_case, use SnakeMapper.

engine, err := pie.NewEngine(
    context.Background(),
    "mydb",
    pie.WithURI("mongodb://localhost:27017"),
    pie.WithMapper(&pie.SnakeMapper{}), // Use SnakeMapper
)

type User struct {
    ID        bson.ObjectID `bson:"_id,omitempty"`
    FirstName string        // Maps to "first_name"
    LastName  string        // Maps to "last_name"
    Email     string        // Maps to "email"
    CreatedAt time.Time     // Maps to "created_at"
}

Custom Mapping

You can implement the pie.Mapper interface to create custom name mapping logic.

type CustomMapper struct{}

func (m *CustomMapper) FieldToBSON(fieldName string) string {
    // Custom logic, e.g., convert to uppercase
    return strings.ToUpper(fieldName)
}

func (m *CustomMapper) BSONToField(bsonName string) string {
    // Custom logic, e.g., convert to lowercase
    return strings.ToLower(bsonName)
}

engine, err := pie.NewEngine(
    context.Background(),
    "mydb",
    pie.WithURI("mongodb://localhost:27017"),
    pie.WithMapper(&CustomMapper{}), // Use custom Mapper
)

Next Steps

• Error Handling - Learn about error handling
• Performance - Learn performance optimization