[![Build Status](https://travis-ci.org/kfly8/p5-Function-Return.svg?branch=master)](https://travis-ci.org/kfly8/p5-Function-Return) [![Coverage Status](https://img.shields.io/coveralls/kfly8/p5-Function-Return/master.svg?style=flat)](https://coveralls.io/r/kfly8/p5-Function-Return?branch=master) [![MetaCPAN Release](https://badge.fury.io/pl/Function-Return.svg)](https://metacpan.org/release/Function-Return) # NAME Function::Return - specify a function return type # SYNOPSIS ```perl use Function::Return; use Types::Standard -types; sub foo :Return(Int) { 123 } sub bar :Return(Int) { 3.14 } foo(); # 123 bar(); # ERROR! Invalid type # multi return values sub baz :Return(Num, Str) { 3.14, 'message' } my ($pi, $msg) = baz(); my $count = baz(); # ERROR! Required list context. # empty return sub boo :Return() { return; } boo(); ``` # DESCRIPTION Function::Return allows you to specify a return type for your functions. ## SUPPORT This module supports all perl versions starting from v5.14. ## IMPORT OPTIONS ### name you can change `Return` to your own name: ```perl use Function::Return name => 'MyReturn'; sub foo :MyReturn(Str) { } ``` ### no\_check you can switch off type check: ```perl use Function::Return no_check => 1; sub foo :Return(Int) { 3.14 } foo(); # NO ERROR! ``` ## METHODS ### Function::Return::info($coderef) The function `Function::Return::info` lets you introspect return values like [Function::Parameters::Info](https://metacpan.org/pod/Function::Parameters::Info): ```perl use Function::Return; fun baz() :Return(Str) { 'hello' } my $rinfo = Function::Return::info \&baz; $rinfo->types; # [Str] $rinfo->isa('Function::Return::Info'); ``` In addition, it can be used with [Function::Parameters](https://metacpan.org/pod/Function::Parameters): ```perl use Function::Parameters; use Function::Return; fun baz() :Return(Str) { 'hello' } my $pinfo = Function::Parameters::info \&baz; my $rinfo = Function::Return::info \&baz; ``` This makes it possible to know both type information of function arguments and return value at compile time, making it easier to use for testing etc. ### Function::Return->wrap\_sub($coderef) This interface is for power-user. Rather than using the `:Return` attribute, it's possible to wrap a coderef like this: ```perl my $wrapped = Function::Return->wrap_sub($orig, [Str]); $wrapped->(); ``` # NOTE ## enforce LIST to simplify `Function::Return` makes the original function is called in list context whether the wrapped function is called in list, scalar, void context: ```perl sub foo :Return(Str) { wantarray ? 'LIST!!' : 'NON!!' } my $a = foo(); # => LIST!! ``` The specified type checks against the value the original function was called in the list context. `wantarray` is convenient, but it sometimes causes confusion. So, in this module, we prioritized that the expected type of function return value becomes easy to understand. ## requirements of type constraint The requirements of type constraint of `Function::Return` is the same as for `Function::Parameters`. Specific requirements are as follows: \> The only requirement is that the returned value (here referred to as $tc, for "type constraint") is an object that provides $tc->check($value) and $tc->get\_message($value) methods. check is called to determine whether a particular value is valid; it should return a true or false value. get\_message is called on values that fail the check test; it should return a string that describes the error. ## compare Return::Type Both `Return::Type` and `Function::Return` perform type checking on the return value of the function, but there are some differences. 1\. `Function::Return` is not possible to specify different type constraints for scalar and list context. 2\. `Function::Return` check type constraint for void context. 3\. `Function::Return::info` and `Function::Parameters::info` can be used together. # SEE ALSO [Function::Parameters](https://metacpan.org/pod/Function::Parameters), [Return::Type](https://metacpan.org/pod/Return::Type) # LICENSE Copyright (C) kfly8. This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. # AUTHOR kfly8