I have a function with interface argument:
func f(e error) {
if e == nil {
fmt.Println("YEY! NIL") // how to get here?
} else {
fmt.Println("NOT NIL :(")
}
}
How do I pass it a nil value via reflect
so that it passes == nil
check?
Approach 1:
func main() {
rf := reflect.ValueOf(f)
nilArg := reflect.Zero(reflect.TypeOf((error)(nil))) // panic: reflect: Zero(nil)
rf.Call([]reflect.Value{nilArg})
}
Approach 2:
type MyError struct{}
func (e MyError) Error() string {
return ""
}
func main() {
rf := reflect.ValueOf(f)
nilArg := reflect.Zero(reflect.TypeOf(&MyError{})) // NOT NIL :(
rf.Call([]reflect.Value{nilArg})
}
Second approach doesn't work due to https://golang.org/doc/faq#nil_error
Playground: https://play.golang.org/p/V0bMSPcCKI