Golang Interface Match

test1_ok.go

package main

import (
    "fmt"
)

type Handler func(int)

func test(handler Handler) {
    handler(1)
}

func main() {
    test(func(i int) {
        fmt.Printf("%d\n", i)
    })
}

test2_fail.go

/**
Compile Failure:
    cannot use new(HandlerImpl) (type *HandlerImpl) as type CanHandle in argument to test:
	*HandlerImpl does not implement CanHandle (wrong type for Handle method)
		have Handle(func(int))
		want Handle(Handler)

Fix method:
  Replace Handler with func(int), or replace func(int) with Handler
**/

package main

import (
    "fmt"
)

type Handler func(int)

type CanHandle interface {
    Handle(Handler)
}

type HandlerImpl struct {
}

func (handler *HandlerImpl) Handle(do func(int)) {
    do(1)
}

func test(handler CanHandle) {
    handler.Handle(func(i int) {
        fmt.Printf("%d\n", i)
    })
}

func main() {
    test(new(HandlerImpl))
}