Question

I try to get a directory listing using this function:

package main;
import ("fmt"; "os"; "io/ioutil")

func main() {
    dir, _ := ioutil.ReadDir("..")
    var f os.FileInfo
    for f = range dir {
        fmt.Println(f.Name())
    }
}

According to the documentation of ReadDir, it should return []os.FileInfo as the first return parameter. When I try to compile it, however, I get

cannot assign type int to f (type os.FileInfo) in range: int does not implement os.FileInfo (missing IsDir method)

What am I missing?

Answer 1

This should work:

for _, f = range dir {
        fmt.Println(f.Name())
    }

You ignore the index and only assign the dir entry.

You don’t have to declare the var if you don’t want. This would also work:

func main() {
    dir, _ := ioutil.ReadDir("..")
    for _, f := range dir {
        fmt.Println(f.Name())
    }
}

Note the ‘:=‘ after ‘_, f‘, instead of your ‘f = ‘.

The issue doesn’t comes from what ReadDir() returns, but comes from the range expression, which returns (index, value).
From the Go Specs “For Statements“:

Range expression                          1st value          2nd value (if 2nd variable is present)

array or slice  a  [n]E, *[n]E, or []E    index    i  int    a[i]       E