gpb_opts - additional documentation and examples...??? about gpb HOT 8 CLOSED

Me again,

First, thank you for all your hard work.

Second, after reading your gpb_compile.erl specifically,

doc

Compile a .proto file to a .erl file and to a .hrl file.

The File must not include path to the .proto file. Example: "SomeDefinitions.proto" is ok, while > >"/path/to/SomeDefinitions.proto" is not ok.

The .proto file is expected to be found in a directories specified by an {i,directory()} option. It is possible to specify {i,directory()} several times, they will be searched in the order specified.

Do I need to manually create the directory mkdir -p? or does

{gpb_opts, [
            {i, "../_build/proto_dir"},

            {module_name_suffix, "_pb"},

            {o_erl, "../_build/out_src"},

            {o_hrl, "../_build/out_include"},

            {strings_as_binaries, true},

            type_specs]}.

create the directory by rebar3 compile ? I tried the rebar3 compile option and directories were not created.

Sorry if this is a real newbie questions.

from gpb.

I think you're missing rebar3 protobuf compile before rebar3 compile.

I think this is actually more of a rebar3_gpb_plugin question than a gpb question, but here's some guidance.

I set up an example app, mylib using just rebar3 new app.

I had the following relevant lines in rebar.config:

{erl_opts, [debug_info, {i, "./_build/default/plugins/gpb/include"}]}.
...
{gpb_opts, [{i, "src"},
            {o_hrl, "include"},
            {o_erl, "src"},
            {module_name_suffix, "_pb"},
            {strings_as_binaries, true},
            type_specs]}.
{provider_hooks, [
    {pre, [{compile, {protobuf, compile}},
           {clean, {protobuf, clean}}]}]}.

And this in src/mylib_x.proto:

message m {
  required uint32 f = 1;
}

I generated mylib_x_pb.erl and mylib_x_pb.hrl into the _build/... dir from src/mylib_x.proto using: rebar3 protobuf compile The rebar3_gpb_plugin compiles .proto files it finds in the directories from the {i,Dir} option(s), and internally prepends the dest build directory to any o_erl and o_hrl options. Directory creation is automatic.

Then I compiled these using rebar3 compile.

To use the generated code, I could call mylib_x_pb:decode_msg(Bin,m) where Bin is some http POSTed data I've got via cowboy. Decoding would give me an #m{}. Or I could call Bin = mylib_x_pb:encode_msg(#m{f=4711}) to get me a binary I could send to cowboy for shipping over http.

Hope this is useful for you

from gpb.

Thank you Tomas, that worked. You were correct I was missing the rebar3 protobuf compile step. I check the directories and it appears all the proper files have been created.

To test,

$ cd myapp
$ rebar3 shell 
1> myapp_pb:   

At this point, the decode or encode functions are not available. I understand your instructions but I'm I loading the myapp_pb incorrectly?

Thank you again for your help

from gpb.

You might need to load the module into the shell before it can expand. For example l(myapp_pb). or m(myapp_pb). The former will load the module. The latter will print some info about it, and to do that, as a side-effect, it will first load the module.

from gpb.

Thank you again!

However, I did learned that using a hyphen - in the file name is a no no

This didn't work:

$ rebar3 shell
1> m(rtb-myapp_pb).
** exception error: an error occurred when evaluating an arithmetic expression
     in operator  -/2
        called as rtb - myapp_pb

This did work

rebar3 shell
1> m(rtb_pb).
Module: rtb_pb
MD5: 819507be6604e......

from gpb.

Yes :) It is possible to have "funny" characters in module names (which are just atoms). You have to quote the atoms, like this: 'rtb-myapp_pb'. But it is generally easier and more common to go with underscores instead of dashes.

from gpb.

I take it your issue with gpb is solved, and we can close this? For general questions about Erlang itself, I thought I should hint about subscribing to the erlang-questions mailing list over at http://www.erlang.org/community/mailinglists

from gpb.

thanks!

from gpb.