Documentation of Haskell libraries #haskell #lantern
While I was improving Lantern I wanted to use the Haskell library Database.PostgreSQL.Simple.Notification to monitor update search index events.
I was a little confused when I read the documentation of
getNotification
and saw that it didn't take what channel to listen on
as an argument - having just read the PostgreSQL documentation of
NOTIFY channel
+ LISTEN channel
that was what I was expecting.
After some digging I found a test for the
library
and from that saw that the way to use D.P.S.Notification is to execute
one or more LISTEN channel
before calling getNotification
.
In hindsight it is obvious (you want to be able to listen to multiple
channels in the same getNotification
call), but to me, as a relative
beginner in Haskell and using postgresql-simple, and never having tried
LISTEN/NOTIFY before, it wasn't.
I have written to the maintainer and suggested that the documentation of D.P.S.Notification mention this.
One thing I miss in the documentation of many Haskell libraries is a couple of lines giving an example of how to use them - luckily I found the solution in a test this time.
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