How to check response returned from tabwriter.Writer in golang

Question

I am writting something to tabwriter.Writer object,

    w := tabwriter.NewWriter(os.Stdout, 5, 1, 3, ' ', 0)
    fmt.Fprintf(w, "%v\t%v\t\n", somevalue1, somevalue2)

I can print the data in w in console using w.Flush() Is there any way so get values in w as string in one place and compare it with some value?

I want to compare what I have in w with some data.

Answer 1

You can implement your own io.Writer :

type W []byte

func (w *W) Write(b []byte) (int, error) {
    *w = append(*w, b...)
    return len(b), nil
}

You can then pass an instance of *W to tabwriter.NewWriter :

sw := &W{}
w := tabwriter.NewWriter(sw, 5, 1, 3, ' ', 0)
fmt.Fprintf(w, "%v\t%v\t\n", somevalue1, somevalue2)

// get the string value from sw
str := string(*sw)

As sugested by @Tim, you should use *bytes.Buffer instead for better performance and it already implements io.Writer :

var b bytes.Buffer
w := tabwriter.NewWriter(&b, 0, 0, 1, '.', 0)
// ...
fmt.Println(b.String())