Embedded Structs

Go is not an object-oriented language. However, embedded structs provide a kind of data-only inheritance that can be useful at times. Keep in mind, Go doesn't support classes or inheritance in the complete sense, but embedded structs are a way to elevate and share fields between struct definitions.

type car struct {
  brand string
  model string
}

type truck struct {
  // "car" is embedded, so the definition of a
  // "truck" now also additionally contains all
  // of the fields of the car struct
  car
  bedSize int
}

Embedded vs. Nested

• Unlike nested structs, an embedded struct's fields are accessed at the top level like normal fields.

• Like nested structs, you assign the promoted fields with the embedded struct in a composite literal.

lanesTruck := truck{
  bedSize: 10,
  car: car{
    brand: "Toyota",
    model: "Tundra",
  },
}

fmt.Println(lanesTruck.brand) // Toyota
fmt.Println(lanesTruck.model) // Tundra

In the example above you can see that both brand and model are accessible from the top-level, while the nested equivalent to this object would require you to access these fields via a nested car struct: lanesTruck.car.brand or lanesTruck.car.model.