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import Data.Maybe | |
data User = User { | |
userId :: Maybe Int, | |
name :: String, | |
age :: Int | |
} deriving (Show) | |
data S3Config = S3Config { | |
region :: String, | |
bucket :: String | |
} deriving (Show) | |
data DBConfig = DBConfig { | |
host :: String, | |
port :: Int | |
} | |
data UserService = UserService { | |
getUser :: Int -> IO User, | |
updateUser :: Int -> User -> IO User | |
} | |
s3Config = S3Config "us-east-1" "bucketName" | |
dbConfig = DBConfig "somehost" 1234 | |
getUserS3 :: S3Config -> Int -> IO User | |
getUserS3 conf uid = do | |
putStrLn "Getting user using S3" | |
return $ User (Just uid) "Some Name" 37 | |
updateUserS3 :: S3Config -> Int -> User -> IO User | |
updateUserS3 conf uid user = do | |
putStrLn "Updating user using S3" | |
return $ User (Just uid) (name user) (age user) | |
getUserDB :: DBConfig -> Int -> IO User | |
getUserDB conf uid = do | |
putStrLn "Getting user using DB" | |
return $ User (Just uid) "Some Name" 37 | |
updateUserDB :: DBConfig -> Int -> User -> IO User | |
updateUserDB conf uid user = do | |
putStrLn "Updating user using DB" | |
return $ User (Just uid) (name user) (age user) | |
getUserMem :: Int -> IO User | |
getUserMem uid = do | |
putStrLn "Getting user using Mem" | |
return $ User (Just uid) "Some Name" 37 | |
updateUserMem :: Int -> User -> IO User | |
updateUserMem uid user = do | |
putStrLn "Updating user using Mem" | |
return $ User (Just uid) (name user) (age user) | |
s3Service = UserService (getUserS3 s3Config) (updateUserS3 s3Config) | |
dbService = UserService (getUserDB dbConfig) (updateUserDB dbConfig) | |
memService = UserService getUserMem updateUserMem | |
-- This is our program that may use different implementation of UserService | |
changeNameProgram :: UserService -> Int -> String -> IO User | |
changeNameProgram uService uid newName = do | |
found <- getUser uService uid | |
updated <- updateUser uService uid (found {name = newName}) | |
return updated | |
res1 = changeNameProgram s3Service 10 "Melissa S3" | |
res2 = changeNameProgram dbService 10 "Melissa DB" | |
res3 = changeNameProgram memService 10 "Melissa Mem" |
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