Be careful. You are correct but newcomers to Go often get confused here.
Printf unpacks the interface it is passed to find the concrete element
inside. Doing what reflect requires you to do to discover the type of
an interface is unrelated to the problem at hand.
Watch:
% cat x.go
package main
one important detail i have not found in the other answers is
that stat is declared to return a fs.FileInfo, but printf takes
an empty interface argument and therefor unwraps the interface
value. so if you want to print the actual variable type of interface
variables you can pass a pointer (same i
On Sun, Mar 6, 2022 at 12:33 PM jlfo...@berkeley.edu
wrote:
> Thanks for the quick reply. Let's say I wanted to pass "fileinfo" from my
> program to another function. What would I say in function's argument list
> for fileinfo's type? From your reply I'm guessing I would give "fileinfo
> *io/fs.f
https://go.dev/play/p/pz02pSaVCyl
A function can return a value of a private type (or a pointer to such a
type, as you found). It's a way to return an opaque value that implements
an interface.
The receiver in a different package can assign that value, but can't
declare additional variables o
Thanks for the quick reply. Let's say I wanted to pass "fileinfo" from my
program to another function. What would I say in function's argument list
for fileinfo's type? From your reply I'm guessing I would give "fileinfo
*io/fs.fileinfo" but I'm not sure.
Jon
On Sunday, March 6, 2022 at 12:2
It's because os.FileInfo is an interface, not a concrete type.
Specifically, it's an alias for io/fs.FileInfo. The concrete type returned
by os.Stat() is os.fileStat; a struct that implements the os.FileInfo
interface. While you can't refer to a private type like os.fileStat there
is nothing prohib
(go version go1.17.7 linux/amd64)
Consider the following trivial program:
--
package main
import (
"fmt"
"os"
)
func main() {
file := "."
fileinfo, _ := os.Stat(file)
fmt.Printf("type of fileinfo = %T\n", fileinfo)
}
--
This runs and produces the
