沒有Yesod，Persistent和MySQL的實例錯誤

我不確定這篇文章中包含什麼，因爲我真的不明白錯誤信息，所以我剛纔包含錯誤，Model.hs文件和模型。我正在使用MySQL的Yesod腳手架站點。我使用的操作系統是Ubuntu。如果您需要查看任何其他代碼，例如數據定義然後只是問。沒有Yesod，Persistent和MySQL的實例錯誤

錯誤消息：

[ 6 of 20] Compiling Model   (src/Model.hs, .stack-work/dist/x86_64-linux/Cabal-1.24.2.0/build/Model.o) 

/home/james/ConVoke/convoke-website/src/Model.hs:24:7: error: 
    • No instance for (persistent-2.7.0:Database.Persist.Sql.Class.PersistFieldSql 
         Language) 
     arising from a use of ‘persistent-2.7.0:Database.Persist.Sql.Class.sqlType’ 
    • In the fourth argument of ‘FieldDef’, namely 
     ‘persistent-2.7.0:Database.Persist.Sql.Class.sqlType 
      (Data.Proxy.Proxy :: Data.Proxy.Proxy Language)’ 
     In the expression: 
     FieldDef 
      (HaskellName (packPTH "language")) 
      (DBName (packPTH "language")) 
      (FTTypeCon Nothing (packPTH "Language")) 
      (persistent-2.7.0:Database.Persist.Sql.Class.sqlType 
      (Data.Proxy.Proxy :: Data.Proxy.Proxy Language)) 
      [] 
      True 
      NoReference 
     In the ‘entityFields’ field of a record 

-- While building package website-0.0.0 using: 
     /home/james/.stack/setup-exe-cache/x86_64-linux/Cabal-simple_mPHDZzAJ_1.24.2.0_ghc-8.0.2 --builddir=.stack-work/dist/x86_64-linux/Cabal-1.24.2.0 build lib:website --ghc-options " -ddump-hi -ddump-to-file"

Model.hs：

{-# LANGUAGE EmptyDataDecls    #-} 
{-# LANGUAGE FlexibleInstances   #-} 
{-# LANGUAGE GADTs      #-} 
{-# LANGUAGE GeneralizedNewtypeDeriving #-} 
{-# LANGUAGE MultiParamTypeClasses  #-} 
{-# LANGUAGE NoImplicitPrelude   #-} 
{-# LANGUAGE OverloadedStrings   #-} 
{-# LANGUAGE TemplateHaskell   #-} 
{-# LANGUAGE TypeFamilies    #-} 
module Model where 

import ClassyPrelude.Yesod 
import Database.Persist.Quasi 

import Import.Game 
import Import.Language 
import Import.Profile 

-- You can define all of your database entities in the entities file. 
-- You can find more information on persistent and how to declare entities 
-- at: 
-- http://www.yesodweb.com/book/persistent/ 
share [mkPersist sqlSettings, mkMigrate "migrateAll"] 
    $(persistFileWith lowerCaseSettings "config/models")

型號：

Player 
    name Text 
    username Text 
    dob Day 
    language Language 
    tournaments [TournamentResult] 
    deriving (Show) 

PlatformAccount 
    player PlayerId 
    platform Platform 
    account Text 
    deriving (Show) 

SocialAccount 
    player PlayerId 
    site SocialSite 
    account Text 
    deriving (Show) 

PastTeam 
    player PlayerId 
    team TeamId 
    yearJoined Int 
    yearLeft Int 
    deriving (Show) 

TournamentResult 
    player PlayerId 
    team TeamId 
    name Text 
    placing Text 
    year Int 
    deriving (Show) 

Roster 
    name Text 
    game Game 
    team TeamId 
    players [PlayerId] 
    creationDay Day 
    deriving (Show) 

PlayerRole 
    roster RosterId 
    player PlayerId 
    role Role 
    deriving (Show) 

CompetitiveGame 
    game Game 
    platform Platform 
    role Role 
    availability Availability 
    playingSince Int 
    deriving (Show) 

Team 
    name Text 
    creationDay Day 
    deriving (Show)

感謝提前:)

編輯：由於所要求的語言。 hs文件定義La語言數據類型：

module Import.Language where 

allLanguages :: [Language] 
allLanguages = [Afrikanns ..] 

data Language = Afrikanns | 
       Albanian | 
       Arabic | 
       Armenian | 
       Basque | 
       Bengali | 
       Bulgarian | 
       Catalan | 
       Cambodian | 
       Chinese_Mandarin | 
       Croation | 
       Czech | 
       Danish | 
       Dutch | 
       English | 
       Estonian | 
       Fiji | 
       Finnish | 
       French | 
       Georgian | 
       German | 
       Greek | 
       Gujarati | 
       Hebrew | 
       Hindi | 
       Hungarian | 
       Icelandic | 
       Indonesian | 
       Irish | 
       Italian | 
       Japanese | 
       Javanese | 
       Korean | 
       Latin | 
       Latvian | 
       Lithuanian | 
       Macedonian | 
       Malay | 
       Malayalam | 
       Maltese | 
       Maori | 
       Marathi | 
       Mongolian | 
       Nepali | 
       Norwegian | 
       Persian | 
       Polish | 
       Portuguese | 
       Punjabi | 
       Quechua | 
       Romanian | 
       Russian | 
       Samoan | 
       Serbian | 
       Slovak | 
       Slovenian | 
       Spanish | 
       Swahili | 
       Swedish | 
       Tamil | 
       Tatar | 
       Telugu | 
       Thai | 
       Tibetan | 
       Tonga | 
       Turkish | 
       Ukranian | 
       Urdu | 
       Uzbek | 
       Vietnamese | 
       Welsh | 
       Xhosa 
       deriving (Enum, Show, Eq)

來源

2017-09-03 James Burton

何處以及如何定義「語言」類型？ – Sibi

@Sibi Language是Language.hs中由我自己定義的數據類型，用於表示用戶可以在其個人資料中選擇的各種語言。它被導入到Model.hs中作爲Import.Language。我其實並沒有想過在錯誤語言和我的數據類型之間的聯繫，我只是認爲它是包的一部分。我想我應該給我的數據類型少通用的名稱，以便他們突出一點XD –

該錯誤表明它無法找到總和類型相關的持久實例。你必須做兩件事來解決它：

=>請務必爲您的總和類型派生Show和Read實例。例如：

data Language = JS | Haskell deriving (Eq, Show, Read, Ord)

=>導出持久相關實例使用模板哈斯克爾它：

derivePersistField "Language"

你必須爲你使用它爲模型中的所有的總和類型做到這一點。

來源

2017-09-03 08:00:54 Sibi

沒有Yesod，Persistent和MySQL的實例錯誤

回答

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