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<H1>[99s-extend] cowboy_http_handler type spec</H1>
<B>Loïc Hoguin</B>
<A HREF="mailto:extend%40lists.ninenines.eu?Subject=Re%3A%20%5B99s-extend%5D%20cowboy_http_handler%20type%20spec&In-Reply-To=%3C5090660A.2000301%40ninenines.eu%3E"
TITLE="[99s-extend] cowboy_http_handler type spec">essen at ninenines.eu
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<I>Wed Oct 31 00:43:06 CET 2012</I>
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<PRE>On 10/31/2012 12:38 AM, rambocoder wrote:
><i> Hi everyone, newb questions here:
</I>><i>
</I>><i> Is the reason why the type specification for the init callback lists
</I>><i> various "{loop,..." tuples, because a single module can implement
</I>><i> cowboy_loop_handler and cowboy_http_handler?
</I>><i> And this way, a dializier warning will not be triggered?
</I>><i> <A HREF="https://github.com/extend/cowboy/blob/master/src/cowboy_http_handler.erl#L39">https://github.com/extend/cowboy/blob/master/src/cowboy_http_handler.erl#L39</A>
</I>
Yes that's exactly why. Not the best solution but good enough.
><i> Because looking at the handler code,
</I>><i> <A HREF="https://github.com/extend/cowboy/blob/master/src/cowboy_protocol.erl#L473">https://github.com/extend/cowboy/blob/master/src/cowboy_protocol.erl#L473</A> if
</I>><i> the {loop, * is returned from init, then the handle(Req,State) will not
</I>><i> be processed.
</I>
You have this one if you just want loops:
<A HREF="https://github.com/extend/cowboy/blob/master/src/cowboy_loop_handler.erl">https://github.com/extend/cowboy/blob/master/src/cowboy_loop_handler.erl</A>
Having an identical init in both allows us to use the 2 handlers without
Dialyzer complaining.
><i> Also, is it safe to say that Handler:init is like "before" in lot's of
</I>><i> web frameworks. I can place validation\authentication logic there.
</I>
Definitely, prepare what you need in init, do what you need to do in
handle and clean up in terminate if needed.
--
Loïc Hoguin
Erlang Cowboy
Nine Nines
<A HREF="http://ninenines.eu">http://ninenines.eu</A>
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