Golang custom type fmt printing

Question

I have a custom type like this:

type Timestamp struct {
    Time time.Time  
}
// some more methods...

Now when I print an instance of it using fmt:

test := Timestamp{
    Time: time.Now(),
}
fmt.Println("TEST:", test)

the output is:

TEST: {2009-11-10 23:00:00 +0000 UTC m=+0.000000001}

How can I add custom formatting to the custom type to pretty print the output like 2009-11-10T23:00:00Z in cases where it should be printed using fmt Functions (Println etc..)?

score 2 · Answer 1 · answered May 01 '20 at 08:27

2

It is as simple as adding this function:

func (ts Timestamp) Format(f fmt.State, c rune) {
    f.Write([]byte(ts.Time.Format(time.RFC3339)))
}

Output:

TEST: 2020-05-01T08:25:14Z

answered May 01 '20 at 08:27

Techradar

3,506
3
18
28

9

A simpler way for most cases is to provide a `String()` method. – Jonathan Hall May 01 '20 at 08:33

Golang custom type fmt printing

1 Answers1