How do I declare a function pointer to a method in Go
And for an example more familiar to those of us used to a typedef
in C for function pointers:
package main
import "fmt"
type DyadicMath func (int, int) int // your function pointer type
func doAdd(one int, two int) (ret int) {
ret = one + two;
return
}
func Work(input []int, addthis int, workfunc DyadicMath) {
for _, val := range input {
fmt.Println("--> ",workfunc(val, addthis))
}
}
func main() {
stuff := []int{ 1,2,3,4,5 }
Work(stuff,10,doAdd)
doMult := func (one int, two int) (ret int) {
ret = one * two;
return
}
Work(stuff,10,doMult)
}
https://play.golang.org/p/G5xzJXLexc
If you want to create a function pointer to a method, you have two ways. The first is essentially turning a method with one argument into a function with two:
type Summable int
func (s Summable) Add(n int) int {
return s+n
}
var f func(s Summable, n int) int = (Summable).Add
// ...
fmt.Println(f(1, 2))
The second way will "bind" the value of s
(at the time of evaluation) to the Summable
receiver method Add
, and then assign it to the variable f
:
s := Summable(1)
var f func(n int) int = s.Add
fmt.Println(f(2))
Playground: http://play.golang.org/p/ctovxsFV2z.
Any changes to s
after f
is assigned will have no affect on the result: https://play.golang.org/p/UhPdYW5wUOP