Can functions be passed as parameters?

In Java I can do something like

derp(new Runnable { public void run () { /* run this sometime later */ } })

and “run” the code in the method later. It’s a pain to handle (anonymous inner class), but it can be done.

Does Go have something that can facilitate a function/callback being passed in as a parameter?

Answer:

Yes, consider some of these examples:

package main
import "fmt"
// convert types take an int and return a string value.
type convert func(int) string
// value implements convert, returning x as string.
func value(x int) string {
    return fmt.Sprintf("%v", x)
}
// quote123 passes 123 to convert func and returns quoted string.
func quote123(fn convert) string {
    return fmt.Sprintf("%q", fn(123))
}
func main() {
    var result string
    result = value(123)
    fmt.Println(result)
    // Output: 123
    result = quote123(value)
    fmt.Println(result)
    // Output: "123"
    result = quote123(func(x int) string { return fmt.Sprintf("%b", x) })
    fmt.Println(result)
    // Output: "1111011"
    foo := func(x int) string { return "foo" }
    result = quote123(foo)
    fmt.Println(result)
    // Output: "foo"
    _ = convert(foo) // confirm foo satisfies convert at runtime
    // fails due to argument type
    // _ = convert(func(x float64) string { return "" })
}

Play: http://play.golang.org/p/XNMtrDUDS0

Tour: https://tour.golang.org/moretypes/25 (Function Closures)