How do you get a function pointer to a typed function in go?

function-pointers, go, pointer-to-member

Solution

You can use method expressions, which will return a function that takes the receiver as the first argument.

f2 := (*x).hello2
fmt.Printf("%+v\n", f2)

f2(&x{}, 123)

Otherwise you can just wrap the function call in a function that accepts the `x` as an argument.

f2 := func(val *x) {
    val.hello2(123)
}

Or that closes over an existing `x` value.

val := &x{}

f2 := func() {
    val.hello2(123)
}

Problem

The following code gets a pointer to the function `hello` and prints it: ``` package main import "fmt" type x struct {} func (self *x) hello2(a int) {} func hello(a int) {} func main() { f1 := hello fmt.Printf("%+v\n", f1) // f2 := hello2 // fmt.Printf("%+v\n", f2) } ``` However, if I un-comment the section at the bottom, the compile errors, saying: ``` > ./junk.go:14: undefined: hello2 ``` So I tried: ``` i := &x{} f2 := &i.hello2 fmt.Printf("%+v\n", f2) ``` ...but that errors with: ``` > ./junk.go:15: method i.hello2 is not an expression, must be called ``` Ok, so maybe I have to directly refer to original type: ``` f2 := x.hello2 fmt.Printf("%+v\n", f2) ``` Nope: ``` > ./junk.go:14: invalid method expression x.hello2 (needs pointer receiver: (*x).hello2) > ./junk.go:14: x.hello2 undefined (type x has no method hello2) ``` This sort of works: ``` i := &x{} f2 := reflect.TypeOf(i).Method(0) fmt.Printf("%+v\n", f2) ``` However, the resulting `f2` is a `reflect.Method`, not a function pointer. :( What is the appropriate syntax here?

Original source