# Serializing a record to JSON with ppx\_yojson\_conv? **URL:** \ **Category:** Learning\ **Created:** [October 28, 2021, 9:10am UTC](https://discuss.ocaml.org/t/serializing-a-record-to-json-with-ppx-yojson-conv/8705 "2021-10-28T09:10:05Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![SeedyROM](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/seedyrom/32/3307_2.png) [@SeedyROM](https://discuss.ocaml.org/u/SeedyROM)\ **Post date:** [October 28, 2021, 9:10am UTC](https://discuss.ocaml.org/t/serializing-a-record-to-json-with-ppx-yojson-conv/8705/1 "2021-10-28T09:10:05Z")
So I’m a complete n00b to OCaml (but not a beginner programmer, the ML style is a bit confusing coming from self teaching) and I’ve been searching endlessly and reading source code to figure out how to serialize a record type into a string… What am I missing? The word serialize never appears in any docs, anywhere. There’s either no examples or no info on how to use the functions themselves, or they’re parsing not generating JSON. I need to know if I’m just dumb or not, [@@deriving yojson] compiles just fine but I have **absolutely** no idea how to actually get it to return back a string or accept the type. Do I need to use the deriving in an interface file? Where did any of you learn how to do this? If I’m dumb please delete this, thanks! PS: I can also get s-expressions to work fine with my derived structs, I think I’m missing some etiquette for how ppx\_deriving works? ---
**Author:** ![CraigFe](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/craigfe/32/1989_2.png) [@CraigFe](https://discuss.ocaml.org/u/CraigFe)\ **Post date:** [October 28, 2021, 9:57am UTC](https://discuss.ocaml.org/t/serializing-a-record-to-json-with-ppx-yojson-conv/8705/2 "2021-10-28T09:57:57Z")
Hi @SeedyROM, Using `ppx_yojson_conv` to go to & from JSON strings should look something like this: ```ocaml type t = { foo : string; bar : int } [@@deriving yojson] let to_json_string t = Yojson.Safe.to_string (yojson_of_t t) let of_json_string s = t_of_yojson (Yojson.Safe.from_string s) ``` You’ll also need to tell your build system about the PPX in some way. If you’re using Dune: ```auto (executable ;; or 'library', or 'test' ... (preprocess (pps ppx_yojson_conv))) ``` Unfortunately, if you _don’t_ declare a dependency on some `ppx_deriving` PPX then the `[@@deriving ...]` will just silently fail to generate anything. If you’re getting errors of the form "Unbound value: `yojson_of_t`" then that’s probably the what’s going on. ---
**Author:** ![SeedyROM](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/seedyrom/32/3307_2.png) [@SeedyROM](https://discuss.ocaml.org/u/SeedyROM)\ **Post date:** [October 28, 2021, 10:02am UTC](https://discuss.ocaml.org/t/serializing-a-record-to-json-with-ppx-yojson-conv/8705/3 "2021-10-28T10:02:09Z")
@CraigFe Interesting! I wasn’t getting silent failures, since I was using the ppx\_jane pps. However the part about defining the to and of functions (edit: rather the code inside those methods) is what I was missing I think? I’m not at home right now so I can’t check, but I think I was expecting something more like Rust’s derive which will code gen those types for me. I’m gonna check in a bit, thanks for quick response! I also think I’m gonna make a blog post on some of these gaps in docs coming from other langs and misconceptions I’ve had. Thanks so much. ---
**Author:** ![Chet\_Murthy](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/chet_murthy/32/1501_2.png) [@Chet\_Murthy](https://discuss.ocaml.org/u/Chet_Murthy)\ **Post date:** [October 28, 2021, 11:08pm UTC](https://discuss.ocaml.org/t/serializing-a-record-to-json-with-ppx-yojson-conv/8705/4 "2021-10-28T23:08:30Z")
Right, the PPX extension codegens the `t_of_yojson` and `yojson_of_t` for you, to-and-from the type of Yojson values. @CraigFe is just adding a nice wrapper, to go back-and-forth to strings. There are functions in the Yojson package to go back-and-forth to other sources/sinks (e.g. channels). P.S. the “t” in `t_of_yojson` comes from the name of the type in the typedef, which was “t”. ---
**Author:** ![SeedyROM](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/seedyrom/32/3307_2.png) [@SeedyROM](https://discuss.ocaml.org/u/SeedyROM)\ **Post date:** [October 29, 2021, 7:33am UTC](https://discuss.ocaml.org/t/serializing-a-record-to-json-with-ppx-yojson-conv/8705/5 "2021-10-29T07:33:20Z")
Yup, it was those generated functions I was looking for, the wrapper finally got it to click for me. My brain went blank on the `t` meaning **my** type as well. Thanks to both of ya’ll for helping me out! Cheers. ---
**Author:** ![yawaramin](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/yawaramin/32/3384_2.png) [@yawaramin](https://discuss.ocaml.org/u/yawaramin)\ **Post date:** [October 29, 2021, 2:29pm UTC](https://discuss.ocaml.org/t/serializing-a-record-to-json-with-ppx-yojson-conv/8705/6 "2021-10-29T14:29:31Z")
Imho, this is a slightly bad naming convention. When generating the functions for a type `t`, the `t_of`/`of_t` parts should be left out from the names. For other names, it’s reasonable to put the type names in the functions. ---
**Author:** ![Chet\_Murthy](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/chet_murthy/32/1501_2.png) [@Chet\_Murthy](https://discuss.ocaml.org/u/Chet_Murthy)\ **Post date:** [October 29, 2021, 7:22pm UTC](https://discuss.ocaml.org/t/serializing-a-record-to-json-with-ppx-yojson-conv/8705/7 "2021-10-29T19:22:19Z")
Yawar, I’m curious why you think this. What naming convention would you think is better? ---
**Author:** ![yawaramin](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/yawaramin/32/3384_2.png) [@yawaramin](https://discuss.ocaml.org/u/yawaramin)\ **Post date:** [October 29, 2021, 9:19pm UTC](https://discuss.ocaml.org/t/serializing-a-record-to-json-with-ppx-yojson-conv/8705/8 "2021-10-29T21:19:55Z")
I think this is better: > If the type is called `t` , the functions generated are `{of,to}_yojson` instead of `t_{of,to}_yojson` . From: [GitHub - ocaml-ppx/ppx\_deriving\_yojson: A Yojson codec generator for OCaml.](https://github.com/ocaml-ppx/ppx_deriving_yojson#syntax) The reason is, if you have a type `t`, it’s certainly going to be in a module named something meaningful i.e. the actual name of the domain entity that the type represents. E.g. `module Person = ...`. Then the conversion functions will be accessible as `Person.of_yojson` and `Person.to_yojson`, instead of `Person.t_of_yojson`/`Person.t_to_yojson`. ---
**Author:** ![Chet\_Murthy](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/chet_murthy/32/1501_2.png) [@Chet\_Murthy](https://discuss.ocaml.org/u/Chet_Murthy)\ **Post date:** [October 29, 2021, 9:27pm UTC](https://discuss.ocaml.org/t/serializing-a-record-to-json-with-ppx-yojson-conv/8705/9 "2021-10-29T21:27:55Z")
Ah, I see it now. You don’t mean “in general”, but rather specifically for the case of a type “t”. Gotit. Thank you for clarifying. I buy your argument.