string(...) function

[simran]

Hi All, 

 

Where can one find the definition of the string(...) function. 

I'm assuming it's a builtin?

I've tried various web searches like: golang [builtin] {functions,string}, etc, but so far i have only bee able to decude (which may be incorrect) from stackoverflow that: 

* func string(...) is builtin?

* It will call a "String(...)" function if one exists for that object/struct?

Would appreciate any pointers to where i can find official documentation for it. 

thanks,

simran.

[Jesse McNelis]

On Mon, Apr 20, 2015 at 11:33 AM, simran <simran...@gmail.com> wrote:

Hi All, 

 

Where can one find the definition of the string(...) function. 

I'm assuming it's a builtin?

It's not a function, it's a conversion.

http://golang.org/ref/spec#Conversions

 

I've tried various web searches like: golang [builtin] {functions,string}, etc, but so far i have only bee able to decude (which may be incorrect) from stackoverflow that: 

* func string(...) is builtin?

* It will call a "String(...)" function if one exists for that object/struct?

It won't.

[simran]

Thankyou Jesse. Much appreciated. Has helped clear a lot of my confusion :) 

[roger peppe]

> Would appreciate any pointers to where i can find official documentation for it.

You might find this useful: http://golang.org/pkg/builtin/

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[Konstantin Khomoutov]

On Mon, 20 Apr 2015 11:33:09 +1000
simran <simran...@gmail.com> wrote:

> Where can one find the definition of the string(...) function.

[...]

> * It will call a "String(...)" function if one exists for that
> object/struct?

In additions to what others have said, this one works in Go the other
way round: the code receiving arbitrary values, which it intends to get
a textual representation of, might "type-assert" the value to an
interface which supports a method of getting that textual
representation.

For instance, the `fmt` standard package implements this approach by
having the Stringer interface [1]. Then, the implementations of
various Print* functions in that package can do something along these
lines:

func PrintAny(v interface{}) {
var s string
switch v.(type) {
case string:
s = v
case Stringer:
// OK, we can ask the value in `v` to give us its
// textual representation as its type sees fit, as it
// supports the `func String() string` method:
s = v.String()
default:
// Well, then use reflection to produce the textual
// representation of the value in `v`.
}
// Output whatever ended up in `s`.
}

All this is explained in detail in [2], which, I'd say, is a must-read
(in its entirety) for any newfangled gopher.

[...]

1. https://golang.org/pkg/fmt/#Stringer
2. https://golang.org/doc/effective_go.html#interface_conversions