On Fri, Oct 7, 2016 at 4:18 PM, sbkim via golang-nuts <golang-nuts@googlegroups.com> wrote: > > If an operand of fmt.Printf implements method String() string, fmt.Printf > respects it and uses it. > But it doesn't if an operand is a a struct that has such an element. > > For example, https://play.golang.org/p/QJC7Q9Kpch: > package main > > import "fmt" > > type Int int > > func (i Int) String() string { return fmt.Sprintf("Int(%d)", int(i)) } > > type Box struct{ elem Int } > > func main() { > format := "%[1]v\t%+[1]v\t%#[1]v\n" > i := Int(73) > fmt.Printf(format, i) > fmt.Printf(format, &Box{i}) > fmt.Printf(format, []Int{i}) > fmt.Printf(format, map[string]Int{"hello":i}) > } > > Output: > Int(73) Int(73) 73 > &{73} &{elem:73} &main.Box{elem:73} > [Int(73)] [Int(73)] []main.Int{73} > map[hello:Int(73)] map[hello:Int(73)] map[string]main.Int{"hello":73} > > In the second line of the output, none of the format specifiers ("%v", > "%+v", "%#v") calls the String() method of Int, in contrast to the first > line. > > Isn't this an inconsistency that should be fixed? Or is it intended > behavior?
It does seem like a bug. Please open a bug report at https://golang.org/issue . Thanks. It is happening because of how the reflect package handles unexported fields. If you change the field name from elem to Elem I think you will get the results you expect. But that is pretty hard to justify. Ian -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
