NAME

Function::Interface - declare typed interface package

SYNOPSIS

Declare typed interface package IFoo:

package IFoo {
    use Function::Interface;
    use Types::Standard -types;

    fun hello(Str $msg) :Return(Str);

    fun add(Int $a, Int $b) :Return(Int);
}

Implements the interface package IFoo:

package Foo {
    use Function::Interface::Impl qw(IFoo);
    use Types::Standard -types;

    fun hello(Str $msg) :Return(Str) {
        return "HELLO $msg";
    }

    fun add(Int $a, Int $b) :Return(Int) {
        return $a + $b;
    }
}

Use the type ImplOf:

package FooService {
    use Function::Interface::Types qw(ImplOf);
    use Function::Parameters;
    use Function::Return;
    use Mouse;

    use aliased 'IFoo';

    fun greet(ImplOf[IFoo] $foo) :Return() {
        print $foo->hello;
        return;
    }
}

my $foo_service = FooService->new;
my $foo = Foo->new; # implements of IFoo

$foo_service->greet($foo);

DESCRIPTION

This module provides a typed interface. Function::Interface declares abstract functions without implementation and defines an interface package. Function::Interface::Impl checks if the abstract functions are implemented at compile time.

SUPPORT

This module supports all perl versions starting from v5.14.

Declare function

Function::Interface provides two new keywords, fun and method, for declaring abstract functions and methods with types:

fun hello(Str $msg) :Return(Str);

method new(Num :$x, Num :$y) :Return(Point);

The method of declaring abstract functions is the same as Function::Parameters and Function::Return.

declare parameters

Function arguments must always specify a variable name and type constraint, and named arguments and optional arguments can optionally be specified:

# positional parameters
# e.g. called `foo(1,2,3)`
fun foo1(Int $a, Int $b, Int $c) :Return();

# named parameters
# e.g. called `bar(x => 123, y => 456)`
fun foo2(Num :$x, Num :$y) :Return();

# optional
# e.g. called `baz()` or `baz('some')`
fun foo3(Str $msg=) :Return();

declare return types

Specify zero or more type constraints for the function's return value:

# zero(empty)
fun bar1() :Return();

# one
fun bar2() :Return(Str);

# two
fun bar3() :Return(Str, Num);

requirements of type constraint

The requirements of type constraint of Function::Interface is the same as for Function::Parameters and Function::Return.

METHODS

Function::Interface::info($interface_package)

The function Function::Interface::info lets you introspect interface functions:

# declare interface package
package IBar {
    use Function::Interface;
    fun hello() :Return();
    fun world() :Return();
}

# introspect
my $info = Function::Interface::info 'IBar';
$info->package; # => IBar
$info->functions; # => list of Function::Interface::Info::Function

It returns either undef if it knows nothing about the interface or an object of Function::Interface::Info.

SEE ALSO

Function::Interface::Impl

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 kfly@cpan.org