Methods and pointer indirection (2)

The equivalent thing happens in the reverse direction.

Functions that take a value argument must take a value of that specific type: 

  1. var v Vertex
  2. fmt.Println(AbsFunc(v))  // OK
  3. fmt.Println(AbsFunc(&v)) // Compile error!

while methods with value receivers take either a value or a pointer as the receiver when they are called: 

  1. var v Vertex
  2. fmt.Println(v.Abs()) // OK
  3. p := &v
  4. fmt.Println(p.Abs()) // OK

In this case, the method call p.Abs() is interpreted as (*p).Abs().

indirection-values.go

  1. package main
  3. import (
  4.     "fmt"
  5.     "math"
  6. )
  8. type Vertex struct {
  9.     X, Y float64
  10. }
  12. func (v Vertex) Abs() float64 {
  13.     return math.Sqrt(v.X*v.X + v.Y*v.Y)
  14. }
  16. func AbsFunc(v Vertex) float64 {
  17.     return math.Sqrt(v.X*v.X + v.Y*v.Y)
  18. }
  20. func main() {
  21.     v := Vertex{3, 4}
  22.     fmt.Println(v.Abs())
  23.     fmt.Println(AbsFunc(v))
  25.     p := &Vertex{4, 3}
  26.     fmt.Println(p.Abs())
  27.     fmt.Println(AbsFunc(*p))
  28. }