hello-ppx_rapper

Hello, ppx_rapper!

Let's take a look at ppx_rapper!

We have already seen what PPXs are, so we are good to go!

Have a look at the Exec module. We converted queries from the hello-caqti-lwt project, to a much shorter syntax. Although, we have to adjust the SQL slightly in order to satisfy ppx_rapper's requirements.

Also take a look Fake_users module for other types of usage, and as always the tests.

NOTE

At the time of writing, it's necessary to run this command in order to have a version of ppx_rapper compatible with the latest Caqti version.

opam pin add git+https://github.com/roddyyaga/ppx_rapper#2222edbbe68db7ba1ab0c7a2688c227ea5c0f230

See ppx_rapper PR#35 for more details

Test via the REPL

As in the previous projects, let's play with our REPL for a bit :)

$ PGHOST=localhost PGDATABASE=caqti_study PGPORT=5433 dune utop

Let's initialize our connection:

# open Repo;;
# let conn = Init.connect_exn ();;
val conn : Caqti_lwt.connection = <module>

We have a new API! We use labeled arguments now, and the connection comes last. That API comes from the ppx_rapper code generation.

# Repo.Exec.resolve_ok_exn @@ Exec.add ~a:1 ~b:2 conn;;
- : int = 3

We can still keep our old API if it were for whatever reason necessary.

# Repo.Exec.resolve_ok_exn @@ Exec.mul conn 3 4 ;;
- : int = 12

We've also got a list of fake users to play with

# open Repo.Fake_users;;
# Repo.Exec.resolve_ok_exn @@ Repo.Fake_users.fake_users () conn |> List.map (fun user -> user.email);;
- : string list =
["[email protected]"; "[email protected]"; "[email protected]";
 "[email protected]"; "[email protected]"]