Interface Exmaple

interfaces.go

package main

type Dog interface {
  Bark() string
  Eat(string)
}

type Bulldog struct {
  Name string
}
func (b *Bulldog) Bark() string {
  return "Woof"
}
func (b *Bulldog) Eat(food string) {
  // Do something with food
}

type Lab struct {
  FirstName string
  LastName string
}
func (l *Lab) Bark() string {
  return "Ruff"
}
func (l *Lab) Eat(food string) {
  // Do something with food
}

type Lion struct {
  Name string
}
func (l *Lion) Meow() string {
  return "Roar"
}

usage.go

package main

func main() {
  dogs := make([]Dog)
  
  james := &Bulldog{Name: "James"}
  ollie := &Bulldog{Name: "Ollie"}
  abbey := &Lab{FirstName: "Abbey", LastName: "Smith"}
  stewie := &Lab{FirstName: "Stewie", LastName: "Smith"}
  simba := &Lion{Name: "Simba"}
  
  // Can do this since they all "implement" Dog meaning they have function that match Dog function sigs
  dogs := append(dogs, james)
  dogs := append(dogs, ollie)
  dogs := append(dogs, abbey)
  dogs := append(dogs, stewie)
  
  // Can't do this!!!
  dogs := append(dogs, simba)
  
  // Since they implement Dog you can now call Bark() regardless of their actually struct type
  dogs[0].Bark()
  dogs[1].Bark()
  dogs[2].Bark()
  dogs[3].Bark()
}