These are my attempts to do a SELECT from three tables. But they don't compile and I don't understand the error (I don't know why it expects a tuple (Entity Issue, b0) instead of the triplet I think the code attempts to get).
Attempt 1:
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeFamilies #-}
module Handler.Support where
import Import hiding ((==.))
import qualified Database.Esqueleto as E
import Database.Esqueleto ((^.), (==.), (&&.))
import Data.Traversable
getSupportR :: CustomerId -> Handler Html
getSupportR customerId = do
customer_issues_followUps_list <- runDB $
E.select $
E.from $ \(i, f, c) -> do
E.where_ (i ^. IssueCustomerId ==. E.val customerId &&. i ^. IssueId ==. f ^. FollowUpIssueId &&. i ^. IssueCustomerId ==. c ^. CustomerId)
return (i, f, c)
let issues = map listToMaybe . group . sort . fst . unzip $ customer_issues_followUps_list
defaultLayout $ do
setTitle "Your Licenses"
$(widgetFile "support-display")
error 1:
/home/hhefesto/dev/laurus-nobilis/src/Handler/Support.hs:41:5: error:
• Couldn't match type ‘(ra, rb, rc)’ with ‘(Entity Issue, b0)’
arising from a functional dependency between:
constraint ‘Database.Esqueleto.Internal.Sql.SqlSelect
(E.SqlExpr (Entity Issue), E.SqlExpr (Entity FollowUp),
E.SqlExpr (Entity Customer))
(Entity Issue, b0)’
arising from a use of ‘E.select’
instance ‘Database.Esqueleto.Internal.Sql.SqlSelect
(a3, b3, c) (ra3, rb3, rc3)’
at <no location info>
• In the second argument of ‘($)’, namely
‘E.select
$ E.from
$ \ (i, f, c)
-> do E.where_
(i ^. IssueCustomerId ==. E.val customerId
&&.
i ^. IssueId ==. f ^. FollowUpIssueId
&&. i ^. IssueCustomerId ==. c ^. CustomerId)
return (i, f, c)’
In a stmt of a 'do' block:
customer_issues_followUps_list <- runDB
$ E.select
$ E.from
$ \ (i, f, c)
-> do E.where_
(i ^. IssueCustomerId
==. E.val customerId
&&.
i ^. IssueId
==. f ^. FollowUpIssueId
&&.
i ^. IssueCustomerId
==. c ^. CustomerId)
return (i, f, c)
In the expression:
do customer_issues_followUps_list <- runDB
$ E.select $ E.from $ \ (i, f, c) -> do ...
let issues
= map listToMaybe . group . sort . fst . unzip
$ customer_issues_followUps_list
defaultLayout
$ do setTitle "Your Licenses"
(do ...)
|
41 | E.select $
| ^^^^^^^^^^...
Attempt 2:
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeFamilies #-}
module Handler.Support where
import Import hiding ((==.))
import qualified Database.Esqueleto as E
import Database.Esqueleto ((^.), (==.), (&&.))
import Data.Traversable
getSupportR :: CustomerId -> Handler Html
getSupportR customerId = do
customer_issues_followUps_list <- runDB $
E.select $
E.from $ \(i `E.InnerJoin` f `E.InnerJoin` c) -> do
E.on (c ^. CustomerId ==. i ^. IssueCustomerId)
E.on (i ^. IssueId ==. f ^. FollowUpIssueId)
E.where_ (i ^. IssueCustomerId ==. E.val customerId)
return (i, f, c)
let issues = map listToMaybe . group . sort . fst . unzip $ customer_issues_followUps_list
defaultLayout $ do
setTitle "Your Licenses"
$(widgetFile "support-display")
error 2:
/home/hhefesto/dev/laurus-nobilis/src/Handler/Support.hs:40:5: error:
• Couldn't match type ‘(ra, rb, rc)’ with ‘(Entity Issue, b0)’
arising from a functional dependency between:
constraint ‘Database.Esqueleto.Internal.Sql.SqlSelect
(E.SqlExpr (Entity Issue), E.SqlExpr (Entity FollowUp),
E.SqlExpr (Entity Customer))
(Entity Issue, b0)’
arising from a use of ‘E.select’
instance ‘Database.Esqueleto.Internal.Sql.SqlSelect
(a2, b2, c) (ra2, rb2, rc2)’
at <no location info>
• In the second argument of ‘($)’, namely
‘E.select
$ E.from
$ \ (i `E.InnerJoin` f `E.InnerJoin` c)
-> do E.on (c ^. CustomerId ==. i ^. IssueCustomerId)
E.on (i ^. IssueId ==. f ^. FollowUpIssueId)
....’
In a stmt of a 'do' block:
customer_issues_followUps_list <- runDB
$ E.select
$ E.from
$ \ (i `E.InnerJoin` f `E.InnerJoin` c)
-> do E.on
(c ^. CustomerId
==. i ^. IssueCustomerId)
E.on
(i ^. IssueId
==. f ^. FollowUpIssueId)
....
In the expression:
do customer_issues_followUps_list <- runDB
$ E.select
$ E.from
$ \ (i `E.InnerJoin` f `E.InnerJoin` c)
-> do ...
let issues
= map listToMaybe . group . sort . fst . unzip
$ customer_issues_followUps_list
defaultLayout
$ do setTitle "Your Licenses"
(do ...)
|
40 | E.select $
| ^^^^^^^^^^...
this is my Persistent model:
Customer
email Text
password Text
firstName Text
lastName Text
address1 Text
address2 Text
city Text
state Text
zipCode Text
country Text
phone Text
organization Text
UniqueCustomer email
deriving Typeable
deriving Show
deriving Eq
deriving Ord
License
licenseAlias Text
expirationDate UTCTime
assignedTo CustomerId
customerId CustomerId
deriving Show
deriving Eq
deriving Ord
Issue
customerId CustomerId
issueSummary Text
issueDetails Text
issueState Int
issueDate UTCTime
deriving Show
deriving Eq
deriving Ord
FollowUp
issueId IssueId
followUpDate UTCTime
followUpAuthor CustomerId
followUpText Text
deriving Show
deriving Eq
deriving Ord
-- Soon to be deleted:
Email
email Text
customerId CustomerId Maybe
verkey Text Maybe
UniqueEmail email
Comment json -- Adding "json" causes ToJSON and FromJSON instances to be derived.
message Text
customerId CustomerId Maybe
deriving Eq
deriving Show
As you may see, the error in both attempts is the same: it expected a tuple instead of a triplet.
Any help would be greatly appreciated :)
The culprits were in the let statement:
let issues = map listToMaybe . group . sort . fst . unzip $ customer_issues_followUps_list
fst and unzip work with tuples, so the compiler implied that customer_issues_followUps_list was a tuple.
To solve the problem just add "-extra" to your package.yml dependencies (or your cabal file) and replace fst and unzip with fst3 and unzip3 in the let statement like so:
let issues = map listToMaybe . group . sort . fst3 . unzip3 $ customer_issues_followUps_list