[erlang-questions] The way of accessing record's attributes.

[Alex Feng]

Thank you all for the detailed explanation, I guess I was trying to use
 "C/C++" way of thinking to understand <record>.

Br,
Alex

2016-11-08 15:41 GMT+01:00 Raimo Niskanen <
raimo+erlang-questions@REDACTED>:

> On Tue, Nov 08, 2016 at 02:12:35PM +0100, Alex Feng wrote:
> > Hi,
> >
> > Does anyone know why erlang has to attach the record's name to be able to
> > access an attribute ?
> > I don't understand, for example, the record "#robot" has been assigned to
> > variable "Crusher", why do we have to use  "Crusher#robot.hobbies"
> instead
> > of "Crusher.hobbies" ?
>
> Records is a compile time syntactical sugar on tagged tuples.
>
> So "Crusher#robot.hobbies" is translated to something like
>   begin robot = element(1, Crusher), element(3, Crusher) end
> if 'hobbies' is the second element of #robot.
>
> The compiler can not know that it is the hobbies field from the #robot
> record you want to extract unless told so.  You may mean the hobbies field
> from the #whatever record.  It could see that it is a #robot record from an
> earlier assignment in the same code and warn about it if it's not,
> but in the general case it can not know what is stored in the variable
> hence leaves it to be solved in runtime.
>
>
> >
> >
> > 5> Crusher = #robot{name="Crusher", hobbies=["Crushing people","petting
> > cats"]}.
> > #robot{name = "Crusher",type = industrial,
> > hobbies = ["Crushing people","petting cats"],
> > details = []}
> > 6> Crusher#robot.hobbies.
> > ["Crushing people","petting cats"]
> >
> >
> > Br,
> > Alex
>
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>
>
> --
>
> / Raimo Niskanen, Erlang/OTP, Ericsson AB
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