Stefan G. > Kelp-0.455 > Kelp::Routes

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NAME ^

Kelp::Routes - Routing for a Kelp app

SYNOPSIS ^

    use Kelp::Routes;
    my $r = Kelp::Routes->new( base => 'MyApp' );
    $r->add( '/home', 'home' );

DESCRIPTION ^

The router provides the connection between the HTTP requests and the web application code. It tells the application "If you see a request coming to *this* URI, send it to *that* subroutine for processing". For example, if a request comes to /home, then send it to sub home in the current namespace. The process of capturing URIs and sending them to their corresponding code is called routing.

This router was specifically crafted as part of the Kelp web framework. It is, however, possible to use it on its own, if needed.

It provides a simple, yet sophisticated routing utilizing Perl 5.10's regular expressions, which makes it fast, robust and reliable.

The routing process can roughly be broken down into three steps:

Adding routes

First you create a router object:

    my $r = Kelp::Routes->new();

Then you add your application's routes and their descriptions:

    $r->add( '/path' => 'Module::function' );
    ...
Matching

Once you have your routes added, you can match with the "match" subroutine.

    $r->match( $path, $method );

The Kelp framework already does matching for you, so you may never have to do your own matching. The above example is provided only for reference.

Building URLs from routes

You can name each of your routes, and use that name later to build a URL:

    $r->add( '/begin' => { to => 'function', name => 'home' } );
    my $url = $r->url('home');    # /begin

This can be used in views and other places where you need the full URL of a route.

PLACEHOLDERS ^

Often routes may get more complicated. They may contain variable parts. For example this one /user/1000 is expected to do something with user ID 1000. So, in this case we need to capture a route that begins with /user/ and then has something else after it.

Naturally, when it comes to capturing routes, the first instinct of the Perl programmer is to use regular expressions, like this:

    qr{/user/(\d+)} -> "sub home"

This module will let you do that, however regular expressions can get very complicated, and it won't be long before you lose track of what does what.

This is why a good router (this one included) allows for named placeholders. These are words prefixed with special symbols, which denote a variable piece in the URI. To use the above example:

    "/user/:id" -> "sub home"

It looks a little cleaner.

Placeholders are variables you place in the route path. They are identified by a prefix character and their names must abide to the rules of a regular Perl variable. If necessary, curly braces can be used to separate placeholders from the rest of the path.

There are three types of place holders:

Explicit

These placeholders begin with a column (:) and must have a value in order for the route to match. All characters are matched, except for the forward slash.

    $r->add( '/user/:id' => 'Module::sub' );
    # /user/a       -> match (id = 'a')
    # /user/123     -> match (id = 123)
    # /user/        -> no match
    # /user         -> no match
    # /user/10/foo  -> no match

    $r->add( '/page/:page/line/:line' => 'Module::sub' );
    # /page/1/line/2        -> match (page = 1, line = 2)
    # /page/bar/line/foo    -> match (page = 'bar', line = 'foo')
    # /page/line/4          -> no match
    # /page/5               -> no match

    $r->add( '/{:a}ing/{:b}ing' => 'Module::sub' );
    # /walking/singing      -> match (a = 'walk', b = 'sing')
    # /cooking/ing          -> no match
    # /ing/ing              -> no match

Optional

Optional placeholders begin with a question mark ? and denote an optional value. You may also specify a default value for the optional placeholder via the "defaults" option. Again, like the explicit placeholders, the optional ones capture all characters, except the forward slash.

    $r->add( '/data/?id' => 'Module::sub' );
    # /bar/foo          -> match ( id = 'foo' )
    # /bar/             -> match ( id = undef )
    # /bar              -> match ( id = undef )

    $r->add( '/:a/?b/:c' => 'Module::sub' );
    # /bar/foo/baz      -> match ( a = 'bar', b = 'foo', c = 'baz' )
    # /bar/foo          -> match ( a = 'bar', b = undef, c = 'foo' )
    # /bar              -> no match
    # /bar/foo/baz/moo  -> no match

Optional default values may be specified via the defaults option.

    $r->add(
        '/user/?name' => {
            to       => 'Module::sub',
            defaults => { name => 'hank' }
        }
    );

    # /user             -> match ( name = 'hank' )
    # /user/            -> match ( name = 'hank' )
    # /user/jane        -> match ( name = 'jane' )
    # /user/jane/cho    -> no match

Wildcards

The wildcard placeholders expect a value and capture all characters, including the forward slash.

    $r->add( '/:a/*b/:c'  => 'Module::sub' );
    # /bar/foo/baz/bat  -> match ( a = 'bar', b = 'foo/baz', c = 'bat' )
    # /bar/bat          -> no match

Using curly braces

Curly braces may be used to separate the placeholders from the rest of the path:

    $r->add( '/{:a}ing/{:b}ing' => 'Module::sub' );
    # /looking/seeing       -> match ( a = 'look', b = 'see' )
    # /ing/ing              -> no match

    $r->add( '/:a/{?b}ing' => 'Module::sub' );
    # /bar/hopping          -> match ( a = 'bar', b = 'hopp' )
    # /bar/ing              -> match ( a = 'bar' )
    # /bar                  -> no match

    $r->add( '/:a/{*b}ing/:c' => 'Module::sub' );
    # /bar/hop/ping/foo     -> match ( a = 'bar', b = 'hop/p', c = 'foo' )
    # /bar/ing/foo          -> no match

BRIDGES ^

The "match" subroutine will stop and return the route that best matches the specified path. If that route is marked as a bridge, then "match" will continue looking for another match, and will eventually return an array of one or more routes. Bridges can be used for authentication or other route preprocessing.

    $r->add( '/users', { to => 'Users::auth', bridge => 1 } );
    $r->add( '/users/:action' => 'Users::dispatch' );

The above example will require /users/profile to go through two subroutines: Users::auth and Users::dispatch:

    my $arr = $r->match('/users/view');
    # $arr is an array of two routes now, the bridge and the last one matched

TREES ^

A quick way to add bridges is to use the "tree" option. It allows you to define all routes under a bridge. Example:

    $r->add(
        '/users' => {
            to   => 'users#auth',
            name => 'users',
            tree => [
                '/profile' => {
                    name => 'profile',
                    to   => 'users#profile'
                },
                '/settings' => {
                    name => 'settings',
                    to   => 'users#settings',
                    tree => [
                        '/email' => { name => 'email', to => 'users#email' },
                        '/login' => { name => 'login', to => 'users#login' }
                    ]
                }
            ]
        }
    );

The above call to add causes the following to occur under the hood:

ATTRIBUTES ^

base

Sets the base class for the routes destinations.

    my $r = Kelp::Routes->new( base => 'MyApp' );

This will prepend MyApp:: to all route destinations.

    $r->add( '/home' => 'home' );          # /home -> MyApp::home
    $r->add( '/user' => 'user#home' );     # /user -> MyApp::User::home
    $r->add( '/view' => 'User::view' );    # /view -> MyApp::User::view

A Kelp application will automatically set this value to the name of the main class. If you need to use a route located in another package, you'll have to wrap it in a local sub:

    # Problem:

    $r->add( '/outside' => 'Outside::Module::route' );
    # /outside -> MyApp::Outside::Module::route
    # (most likely not what you want)

    # Solution:

    $r->add( '/outside' => 'outside' );
    ...
    sub outside {
        return Outside::Module::route;
    }

SUBROUTINES ^

add

Adds a new route definition to the routes array.

    $r->add( $path, $destination );

$path can be a path string, e.g. '/user/view' or an ARRAY containing a method and a path, e.g. [ PUT => '/item' ].

The route destination is very flexible. It can be one of these three things:

Destination Options

There are a number of options you can add to modify the behavior of the route, if you specify a hashref for a destination:

to

Sets the destination for the route. It should be a subroutine name or CODE reference.

    $r->add( '/user' => { to => 'users#home' } ); # /home -> MyApp::Users::home
    $r->add( '/sys' => { to => sub { ... } });    # /sys -> execute code
    $r->add( '/item' => { to => 'Items::handle' } ) ;   # /item -> MyApp::Items::handle
    $r->add( '/item' => { to => 'Items::handle' } );    # Same as above

via

Specifies an HTTP method to be considered by "match" when matching a route.

    # POST /item -> MyApp::Items::add
    $r->add(
        '/item' => {
            via => 'POST',
            to  => 'items#add'
        }
    );

A shortcut for the above is this:

    $r->add( [ POST => '/item' ] => 'items#add' );

name

Give the route a name, and you can always use it to build a URL later via the "url" subroutine.

    $r->add(
        '/item/:id/:name' => {
            to   => 'items#view',
            name => 'item'
        }
    );

    # Later
    $r->url( 'item', id => 8, name => 'foo' );    # /item/8/foo

check

A hashref of checks to perform on the captures. It should contain capture names and stringified regular expressions. Do not use ^ and $ to denote beginning and ending of the matched expression, because it will get embedded in a bigger Regexp.

    $r->add(
        '/item/:id/:name' => {
            to    => 'items#view',
            check => {
                id   => '\d+',          # id must be a digit
                name => 'open|close'    # name can be 'open' or 'close'
            }
          }
    );

defaults

Set default values for optional placeholders.

    $r->add(
        '/pages/?id' => {
            to       => 'pages#view',
            defaults => { id => 2 }
        }
    );

    # /pages    -> match ( id = 2 )
    # /pages/   -> match ( id = 2 )
    # /pages/4  -> match ( id = 4 )

bridge

If set to one this route will be treated as a bridge. Please see "bridges" for more information.

tree

Creates a tree of sub-routes. See "trees" for more information and examples.

match

Returns an array of Kelp::Routes::Pattern objects that match the path and HTTP method provided. Each object will contain a hash with the named placeholders in "named" in Kelp::Routes::Pattern, and an array with their values in the order they were specified in the pattern in "param" in Kelp::Routes::Pattern.

    $r->add( '/:id/:name', "route" );
    for my $pattern ( @{ $r->match('/15/alex') } ) {
        $pattern->named;    # { id => 15, name => 'alex' }
        $pattern->param;    # [ 15, 'alex' ]
    }

Routes that used regular expressions instead of patterns will only initialize the param array with the regex captures, unless those patterns are using named captures in which case the named hash will also be initialized.

ACKNOWLEDGEMENTS ^

This module was inspired by Routes::Tiny.

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