Re: [go-nuts] Example of printing in go.dev
On Wed, Mar 9, 2022 at 7:44 PM Nikhilesh Susarla
wrote:
> Okay. I get it.
> When I ran through go playground I missed that type receiver was of
> pointer type, so I was not sure why it didn't print as mentioned in the docs
>
It doesn't matter that the receiver "was of pointer type". That's just an
optimization to avoid copying a, possibly large, object before calling it's
String() method. Go ahead and modify the example to use a non-pointer
receiver. It should behave the same (it does for me).
> On Thursday, 10 March 2022 at 09:00:49 UTC+5:30 kortschak wrote:
>
>> On Wed, 2022-03-09 at 19:16 -0800, Nikhilesh Susarla wrote:
>> > In https://go.dev/doc/effective_go#printing
>> > I saw an example for printing our custom string output for the type.
>> > The code below is from docs.
>> > func (t *T) String() string {
>> > return fmt.Sprintf("%d/%g/%q", t.a, t.b, t.c)
>> > }
>> > fmt.Printf("%v\n", t)
>> >
>> >
>> > But rather the statement should be this right? fmt.Printf("%v\n",
>> > t.String())
>> > Am I missing something?
>> >
>>
>> When the %v (or %s, %q and others[1]) verbs are used the `String()
>> string` is used to construct the printed value.
>>
>> You can see the logic here[2].
>>
>> [1]
>>
>> https://github.com/golang/go/blob/00535b839841227ba60c2de78fbf767088f865bc/src/fmt/print.go#L611
>> [2]
>>
>> https://github.com/golang/go/blob/00535b839841227ba60c2de78fbf767088f865bc/src/fmt/print.go#L623-L628
>>
>>
>> --
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>
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Kurtis Rader
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Re: [go-nuts] Example of printing in go.dev
Okay. I get it.
When I ran through go playground I missed that type receiver was of pointer
type, so I was not sure why it didn't print as mentioned in the docs
Thank you
On Thursday, 10 March 2022 at 09:00:49 UTC+5:30 kortschak wrote:
> On Wed, 2022-03-09 at 19:16 -0800, Nikhilesh Susarla wrote:
> > In https://go.dev/doc/effective_go#printing
> > I saw an example for printing our custom string output for the type.
> > The code below is from docs.
> > func (t *T) String() string {
> > return fmt.Sprintf("%d/%g/%q", t.a, t.b, t.c)
> > }
> > fmt.Printf("%v\n", t)
> >
> >
> > But rather the statement should be this right? fmt.Printf("%v\n",
> > t.String())
> > Am I missing something?
> >
>
> When the %v (or %s, %q and others[1]) verbs are used the `String()
> string` is used to construct the printed value.
>
> You can see the logic here[2].
>
> [1]
>
> https://github.com/golang/go/blob/00535b839841227ba60c2de78fbf767088f865bc/src/fmt/print.go#L611
> [2]
>
> https://github.com/golang/go/blob/00535b839841227ba60c2de78fbf767088f865bc/src/fmt/print.go#L623-L628
>
>
>
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Re: [go-nuts] Example of printing in go.dev
On Wed, Mar 9, 2022 at 7:18 PM Nikhilesh Susarla
wrote:
> In https://go.dev/doc/effective_go#printing
> I saw an example for printing our custom string output for the type.
> The code below is from docs.
> func (t *T) String() string {
> return fmt.Sprintf("%d/%g/%q", t.a, t.b, t.c)
> }
> fmt.Printf("%v\n", t)
>
>
> But rather the statement should be this right? fmt.Printf("%v\n",
> t.String())
> Am I missing something?
>
An object with a String() method causes that method to be used wherever a
string is desired. This includes the `%s` and `%v` formatting verbs. From
the paragraph preceding the example:
> If you want to control the default format for a custom type, all that's
required is to define a method with the signature String() string on the
type.
--
Kurtis Rader
Caretaker of the exceptional canines Junior and Hank
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Re: [go-nuts] Example of printing in go.dev
On Wed, 2022-03-09 at 19:16 -0800, Nikhilesh Susarla wrote:
> In https://go.dev/doc/effective_go#printing
> I saw an example for printing our custom string output for the type.
> The code below is from docs.
> func (t *T) String() string {
> return fmt.Sprintf("%d/%g/%q", t.a, t.b, t.c)
> }
> fmt.Printf("%v\n", t)
>
>
> But rather the statement should be this right? fmt.Printf("%v\n",
> t.String())
> Am I missing something?
>
When the %v (or %s, %q and others[1]) verbs are used the `String()
string` is used to construct the printed value.
You can see the logic here[2].
[1]
https://github.com/golang/go/blob/00535b839841227ba60c2de78fbf767088f865bc/src/fmt/print.go#L611
[2]
https://github.com/golang/go/blob/00535b839841227ba60c2de78fbf767088f865bc/src/fmt/print.go#L623-L628
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[go-nuts] Example of printing in go.dev
In https://go.dev/doc/effective_go#printing
I saw an example for printing our custom string output for the type.
The code below is from docs.
func (t *T) String() string {
return fmt.Sprintf("%d/%g/%q", t.a, t.b, t.c)
}
fmt.Printf("%v\n", t)
But rather the statement should be this right? fmt.Printf("%v\n",
t.String())
Am I missing something?
Thank you
Nikhilesh
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