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

Roger Lipscombe roger@REDACTED
Tue Jun 17 16:21:15 CEST 2014

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,
handle_foo(#state { type = baz }) ->
    ParentId = State#state.parent_id,

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

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?


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