[erlang-questions] Style question: accessing record fields in a function clause pattern match?

[Daniil Churikov]

I am trying to stick to the rule: if match header longer then 80 chars then 
I move all
the variables bindings to function body, so only necessary to proper 
matching parts
will be left.

On Tuesday, June 17, 2014 6:21:27 PM UTC+4, Roger Lipscombe wrote:
>
> I'm currently refactoring some code, and I've got something like this: 
>
> handle_foo(#state { type = bar, id = Id }) -> whatever; 
> handle_foo(#state { type = baz, parent_id = ParentId }) -> whatever. 
>
> ...and I'm wondering whether it's considered bad form to access record 
> fields at the same time as matching them in a function clause. I'm 
> matching on 'type', and accessing 'id' at the same time, I mean. 
>
> Instead, should I consider something like the following? 
>
> handle_foo(#state { type = bar }) -> 
>     Id = State#state.id, 
>     whatever; 
> handle_foo(#state { type = baz }) -> 
>     ParentId = State#state.parent_id, 
>     whatever. 
>
> The first form makes it explicit that for different types, different 
> fields matter (which might be a smell by itself), but it gets hard to 
> see the match on 'type' once I'm accessing more than one or two 
> fields. 
>
> I know this is stylistic, and there's no "right" answer; I just 
> wondered what other people tend to do? 
>
> Or, more generally, do people prefer using pattern matching to access 
> record values, or plain-ol' Foo = State#state.foo expressions? 
>
> Thanks, 
> Roger. 
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