Structs

A struct is simply a collection of fields:

type Pony struct {
  Name           string
  Height, Weight float64
  FavoriteFoods  []string
}

func main() {
  dave := Pony{"Dave", 3.2, 100, []string{"pie"}} // using a struct literal
  alice := Pony{Name: "Alice", Weight:100, Height:3.2, FavoriteFoods:[]string{"kale"}}
  carol := Pony{Name:"carol"} // not all params need to be specified
  e := Pony{} // all values zeroed
  p := &Pony{} // *Pony
  p2 := new(Pony) // all values zeroed, as usual with new

  dave.Name = "Davey" // dot operator can be used to access
  p.Name = "Peter" // Go can implicitly dereference for this
}

As can be seen, structs can be defined with either an ordered literal, or a literal with named arguments.

Structs can be output with fmt.Println, although there are other methods with more convenient formatting.

Methods

Go does not have classes, but any type in Go can have a method.

func (p Pony) PrintFavorites() {
  fmt.Println(p.Name, "likes", strings.Join(p.FavoriteFoods,","))
}

func main() {
  dave := Pony{"dave", 3.2, 100, []string{"carrot", "broccoli"}}
  dave.PrintFavorites() // dave likes carrot,broccoli
}

Value Receivers

Methods with value receivers, as seen above, operate on copies of the original value. Because of this, changing attributes of the received value does not affect the original.

Pointer Receivers

Methods with pointer receivers can modify the value to which the receiver points. These are often more common than value receivers.

func (p *Pony) AddFavorite(f string) {
  p.FavoriteFoods = append(p.FavoriteFoods, f)
}

func main() {
  dave := Pony{"dave", 3.2, 100, []string{"carrot", "broccoli"}}
  dave.AddFavorite("spaghetti")
  dave.PrintFavorites() // dave likes carrot,broccoli,spaghetti
}