package Rinci::FAQ; # just to make PodWeaver happy

# DATE
# VERSION

1;
# ABSTRACT: Metadata for your functions/methods

__END__

=pod

=encoding UTF-8

=head1 NAME

Rinci::FAQ - Metadata for your functions/methods

=head1 VERSION

This document describes version 1.1.94 of Rinci::FAQ (from Perl distribution Rinci), released on 2020-09-23.

=head1 FAQ

=head2 Rinci::function

=over

=item * Why do you make enveloped result an arary instead of hash?

For example, a hash-based enveloped result can be something like:

 {status=>200, message=>"OK", result=>42, meta1=>..., meta2=>...}

This has the benefit of a single container, but I picked array because of the
brevity for simple cases (which are the majority), e.g.:

 [200]        # versus {status=>200}
 [200, "OK"]  # versus {status=>200, message=>"OK"}

When handling enveloped result, the array version is also shorter:

 if ($res->[0] == 200) { ... }
 # versus: if ($res->{status} == 200) { ... }

 print "Error $res->[0] - $res->[1]";
 # versus: print "Error $res->{status} - $res->{message}";

The hash version is more obvious for first-time reader, but after just some
amount of time, C<< $res->[0] >>, C<< $res->[1] >> will become obvious if you
use it consistently.

As a bonus, arrays are faster and more space-efficient than hashes.

=item * How do you indicate transient/temporary vs permanent errors?

Some protocols, like SMTP or POP, defines 4xx codes as temporary errors and 5xx
as permanent ones. This gives clue to clients whether to retry or not. HTTP,
which Rinci is modelled after, does not provide such distinction to its status
codes. However, Rinci defines a C<perm_err> result metadata that can be used for
such purpose, e.g.:

 [500, "Can't submit mail, we are being blocked by RBL", undef,
  {perm_err=>0}]

 [500, "Can't submit mail, destination address does not exist", undef,
  {perm_err=>1}]

=item * How to handle binary data?

To accept binary data, you can set one or more arguments as having the schema
type C<buf> (instead of C<str>):

 args => {
     data => { schema => 'buf*', req=>1 },
 }

To return binary data, you can set result's schema type to C<buf>, e.g.:

 result => { schema => 'buf*' }

For handling binary data when writing Perl-based command-line applications, see
L<Perinci::CmdLine::Manual::Examples>.

=item * How to accept partial data?

First, set an argument property C<partial> to true to signify that this argument
accept partial value. You can then call with special arguments C<-arg_len>,
C<-arg_part_start>, C<-arg_part_len>. See L<Rinci::function> for more details.
L<Riap::HTTP> can also do this via HTTP Content-Range.

=item * How to accept streaming input?

Many program environments (like in Unix) have the concept of standard input.
Rinci provides a thin abstraction over this. You can set the argument property
C<stream> to true. This way, in most implementation like in Perl, your function
will receive the argument value as filehandle which it can then read from. See
C<partial> property in C<args> function metadata property in L<Rinci::function>
for an example.

Your function can also read from standard input directly, but this means you
cannot use conveniences like the C<cmdline_src>, where the command-line
framework can supply an argument value for you from various sources including
standard input and/or files.

=item * How to produce streaming output?

Many program environments (like in Unix) have the concept of standard output. To
produce output stream, you can set result metadata property C<stream> to true.
And then in the result you can put a filehandle or an object that responds to
getline/getitem methods.

=item * What is the difference between accepting partial data and streaming input?

If a function accepts partial data, to send a large data without taking up too
much memory, a caller needs to break the data into several parts and call the
function several times, each with a different part.

If a function accepts a stream input, to send a large data a caller can send a
filehandle/iterator object from which the function can read the data
iteratively.

Stream input is easier and simpler for the function writer to write. A caller
also only needs to call the function once instead of multiple times. However,
there is no resume capability.

On the other hand, partial input data is easier to implement with Riap::HTTP, as
it maps rather closely to HTTP Content-Range.

If you are uploading a large data over a network to a function, partial input
data is preferred because of its ease to work with HTTP and its resume ability.

However, if input is really a stream (i.e. unknown/infinite length), then
streaming input is the option to use.

=item * What is the difference between returning partial result and streaming output?

If a function can return partial result, to retrieve a large result from a
function a caller can calls several times and each time request to retrieve
parts of result.

If a function returns output stream, a caller can then retrieve data from the
stream iteratively.

Output stream is easier to handle by the caller. The caller also only needs to
call once instead of multiple times. However, there is no resume capability.

On the other hand, partial result is easier to implement with Riap::HTTP, as it
maps rather closely to HTTP Content-Range.

If you are retrieving a large data over a network from a function, partial
result is preferred because of its ease to work with HTTP

=back

=head1 HOMEPAGE

Please visit the project's homepage at L<https://metacpan.org/release/Rinci>.

=head1 SOURCE

Source repository is at L<https://github.com/perlancar/perl-Rinci>.

=head1 BUGS

Please report any bugs or feature requests on the bugtracker website L<https://rt.cpan.org/Public/Dist/Display.html?Name=Rinci>

When submitting a bug or request, please include a test-file or a
patch to an existing test-file that illustrates the bug or desired
feature.

=head1 AUTHOR

perlancar <perlancar@cpan.org>

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2020, 2019, 2018, 2017, 2016, 2015, 2014, 2013, 2012 by perlancar@cpan.org.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut
