When it comes to implementing callbacks of a behaviour (e.g., GenServer) I always struggle whether I should add the @impl-attribute to all function clauses or just to the first. def Worker do use GenServer @impl true def handle_call(:foo, from, state) do # .. end @impl true def …

Hello, I just add @impl true just to the first function. The benefit of @impl is to get warnings from the compiler and this will be reached with one annotation.

It’s worth noting that another benefit of @impl is to signal to the programmer that something is, indeed, a callback implementation. This isn’t as apparent in something as ubiquitous as a GenServer, but when reading a module implementing a less well-known or custom behaviour, this is really nice-to…

It’s a little weird, but my personal style is to put the @impl on a standalone function head (when defining multiple clauses for the function). def Worker do use GenServer @impl GenServer def handle_call(request, from, state) def handle_call(:foo, from, state) do # .. end def h…

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@impl-attribute on multi-clause functions

Questions & Help Questions

sodapopcan March 1, 2021, 3:53pm 2

Only the first one is necessary.