Inheritance in Go
Although Go is an object-oriented language, it adopts a different philosphy than more object-oritented language such as C# and java. According to Gang of 4 [1], designs should "prefer composition to inheritance". Go uses a concept called embedding [2] to solve inheritance in a way that looks like composition.
Here is an example of inheritance in Golang.
// go run inheritance.go
package main
import "fmt"
type Fruit struct{
name string
seeds int
}
func (f Fruit) countForSeeds(){
fmt.Printf("%s have %d seeds\n", f.name, f.seeds)
}
type Apple struct{
Fruit
}
func main(){
var f = Fruit{"Fruit", 2}
f.countForSeeds()
var apple = Apple{Fruit{"Apple", 1}}
apple.countForSeeds()
}
You should see the folllowing output.
Fruit have 2 seeds
Apple have 1 seeds
Notice that we embeded Fruit class into Apple struct as an anoynumous field. Although it does look more like struct composition, especially passing a new Fruit struct object into Apply, we are using the parent method countForSeeds() from a subclass. Unfortunately, there is no way to override the parent methods as all the functions are non-virtual, but you can shadow the method. An example is shownn below:
// go run shadow.go
package main
import "fmt"
type Fruit struct{
name string
seeds int
}
func (f Fruit) countForSeeds(){
fmt.Printf("%s have %d seeds\n", f.name, f.seeds)
}
func (a Apple) countForSeeds(){
fmt.Printf("%s is an apple with %d seeds\n", a.name, a.seeds)
}
type Apple struct{
Fruit
}
func main(){
var f = Fruit{"Fruit", 2}
f.countForSeeds()
var apple = Apple{Fruit{"Apple", 1}}
apple.countForSeeds()
}
You should see the following output:
Fruit have 2 seeds
Apple is an apple with 1 seeds