DbConnection or IO(DbConnection)

[tonyday]

Hi

[@DrBoolean - Thank you. Great content and (for my taste) an eminently readable style. It is rare for technical book to make me chuckle.]

In Chapter 8 I am battling to figure out how connectDb has a type of Config -> Either(Error, IO(DbConnection)) given that Postgres.connect only has a type of Url -> DbConnection.
How does the DbConnection become an IO(DbConnection) ?
Am I confused or is there an IO.for missing somewhere ?

[xujihui1985]

yes, I have the same confuse,

// dbUrl :: Config -> Either(Error, url)
var dbUrl = function(c) {
  return (c.uname && c.pass && c.host && c.db)
    ? Right.of("db:pg://"+c.uname+":"+c.pass+"@"+c.host+"5432/"+c.db)
    : Left.of(Error("Invalid config!"));
}

dbUrl takes a config object and return an Either monad, and connectDb map over it, calling it should return an Either(Error, DbConnection)

//  connectDb :: Config -> Either(Error, DbConnection)
var connectDb = compose(map(Postgres.connect), dbUrl);

[DrBoolean]

Totally correct! Sorry, that's my mistake. Good eyes :) I'll update.