NAME
Catalyst::Controller::Constraints - Constraint Signatures for Controller Actions
VERSION
0.10_01 - First Development Release. Production use not recommended yet.
SYNOPSIS
package MyApp::Controller::Foo;
...
use base qw(Catalyst::Controller::Constraints);
__PACKAGE__->config(
constraints => {
# allow only digits for type 'Integer'
Integer => qr/^\d+$/,
# allow only word chars for type 'Word'
Word => sub { /^\w+$/ },
# validate user id and inflate to object
User => {
# check the user id
check => sub {
my ( $self, $c, $id ) = @_;
return $c->is_valid_user_id( $id );
},
# forward to this action if the validation failed
on_fail => 'invalid_user',
# if value is valid, run it through this filter
# afterwards
post_filter => sub {
my ( $self, $c, $id ) = @_;
$c->fetch_user_by_id( $id );
},
}
# inheritance
HighInteger => {
inherit_from => 'Integer',
check => sub { $_ > 22 },
},
# collapse multiple arguments
MyDate => {
# take three integers and return one value
takes => 3,
gives => 1,
# inflate to a datetime object
post_filter => sub {
my ( $self, $c, $y, $m, $d ) = @_;
DateTime->new(
year => $y, month => $m, day => $d );
}
}
}
);
# add two integers, just throws exception on constraint failure
sub add : Local Args(2) Constraints(Integer a, Integer b) {
my ( $self, $c ) = @_;
$c->res->body( $_{a} + $_{b} );
}
# puts the word into the stash, under the key 'foo'
sub stashword : Local Args(1) Constraints( Word foo* ) { }
# user_obj ends as a user object in the stash
sub view_user : Local Args(1) Constraints( User user_obj* ) { }
sub invalid_user : Private {
# handle invalid userid
}
1;
DESCRIPTION
This controller base class for Catalyst enables you to apply constraints to your action arguments.
USAGE
This describes how this controller base class is used. The first thing that has to be done is to use this instead of Catalyst::Controller
as base class:
package MyApp::Controller::Foo;
...
use base qw(Catalyst::Controller::Constraints);
...
Defining Constraints
A constraint definition has no needed keys, though the check
option is the most important. It can contain a code reference, a regular expression reference, or an array reference, containing a list of the former stated:
MyNumA => { check => qr/^\d+$/ },
MyNumB => { check => sub { $_ =~ qr/^\d+$/ } },
MyNumC => { check => [qr/^\d+$/, sub { $_ > 23 }] },
If you just want to supply a check var, you can shortcut that:
MyNumA => qr/^\d+$/,
As you can see, the arguments value is localized to $_ in your code reference to keep the definitions more readable. The @_
array contains the controller, the context, and then the constraints arguments, like an action working with the values.
There are some more options to specify, but let's walk them through step by step. There's a index of them at the bottom for quick referencing.
In every callback (pre_filter
, check
and post_filter
) you are provided with the controller and context objects through $_{ctrl}
and $_{ctx}
. There's also has_param
and param
, but we'll be talking about them later.
There are three possible sources for constraint definitions:
- Shipped constraints
-
See "Default Constraints" for information on which constraints are shipped and ready to use.
- Constraints defined application wide
-
Constraints that are placed in your application config under the
constraints
key are available to the whole application. Any settings made under the name of a shipped constraint are merged together with the shipped config. The application constraints have, of course, priority over the shipped ones. The merging is especially useful to define app and per-controller actions for "Handling Validation Errors". Here is an example:package MyApp; use Catalyst/ -Debug /; __PACKAGE__->config( constraints => { EvenNumber => { check => sub { $_ % 2 }, on_fail => 'odd_number', }, Int => { on_fail => 'not_an_integer', }, }, );
- Constraints defined for one controller
-
These definitions look exactly as those for application wide constraints as they're introduced above. They differ in that they are only defined for the current controller, and have priority over shipped and application wide constraints.
For more control over the error message sent to the user, there is a function available named _()
. A call to _( 'foobar' )
will throw a validation exception that can be handled (See "Handling Validation Errors"). The exception will have it's user_msg
field set to the passed value.
Applying Constraints To Actions
The default constraint attribute name is Constraints
, but you can change that with
__PACKAGE__->config( constraint_attribute => 'Foo' );
in either your application or your controller. The constraints itself are just applied to actions through this attribute's parameter, as usual in Catalyst:
sub foo : Local Constraint( Int bar, Int baz ) { ... }
You don't have to specify a constraint name. If you'd just do a
sub foo : Local Constraint( Int bar, baz ) { ... }
then baz
wouldn't be checked by any constraint. But you could still reference it by name. This can also be combined with another convenience function, autostashing:
sub foo : Local Constraint( bar*, baz* ) { ... }
would when, for example, called with foo/23/17
set the values bar
and baz
in the stash to the corresponding values.
The original, unfiltered and unchanged values are passed to the action through @_
, so this controller base class doesn't interfere with Catalyst's argument passing style at all. However, you can also access the values through the global %_
hash. In the above example, $_{bar}
would be 23
and $_{baz}
would be set to 17
.
Handling Validation Errors
Through the on_fail
option it's possible to handle a validation error of check
. It's value can be a code reference, treated like an action, and a relative or absolute private action path. It's arguments will be The current controller, the context, and the exception object with the following fields:
- constraint
-
This is the name of the constraint type, for example,
Int
. - value
-
The value that didn't pass the inspection.
- user_msg
-
Will be set to the value passed to
_()
if the exception was raised by this function. - argument
-
The name of the argument that didn't pass the validation.
Here is a complete example:
package MyApp::Controller::Foo;
use base qw(Catalyst::Controller::Constraints);
__PACKAGE__->config(
constraints => {
MyInt => {
check => qr/^\d+$/,
on_fail => 'invalid_input',
},
}
);
sub add : Local Args(2) Constraints( MyInt a, MyInt b ) {
$_[1]->response->body( $_{a} + $_{b} );
}
sub invalid_input : Private {
my ( $self, $c, $e ) = @_;
$c->res->body(
sprintf 'Invalid format of %s for %s: %s',
$e->constraint,
$e->argument,
$e->value,
);
}
1;
Constraint Inheritance
Sometimes you don't want to override a constraint's behaviour, but rather add another layer above it. This is where constraint inheritance comes in:
Word => qr/^\w*$/,
UserName => sub { length $_ > 5 },
Using And Collapsing Multiple Arguments
Some arguments consist of more than one value, a date for example. You might want to use three values to create a datetime object. This is a simple example of this:
MyDate => {
takes => 3,
gives => 1,
post_filter => sub {
my ( $self, $c, $y, $m, $d ) = @_;
DateTime->new( year => $y, month => $m, day => $d );
}
}
Note the takes
and gives
values. The first indicates that this constraint takes the next three arguments, not just one. This has as consequence that pre_filter
, post_filter
, check
and the exception objects value
field contain a hashreference. Their return values are stored in an array reference, too. So a pre_filter
that takes more than one value, but returns only one, results in an arrayref in the next calls (check
and post_filter
as value.
The gives
value only affects how the value is passed to the dispatched action. A value of 1 (default is the value of takes
, which has a default of 1) sets the value in %_
directly, rather than through an array reference.
Pre- And Post-Filters
This is pretty simple. These are callbacks that are called before and after check
is running. They receive the value(s) in $_
and starting with index 2 in @_
. Their return value is used as new value for the next calls.
Constraint Parameters
To prevent the need for many equal constraints, it is possible to pass a parameter to them. Usage examples would be Model constraints, that check for existance, permission and load the row from the database. A parameter can be passed to a constraint with [...]
directly after its name:
sub foo : Local Constraint( Model[Category] cat* ) { ... }
(This would also autostash the resulting object, due to *
.)
Access to the parameter is provided through the global %_
hashes key param
, read: $_{param}
. To find out if a parameter was actually provided, you can check $_{has_param}
.
Default Constraints
To set the on_fail
handler for shipped constraints, override those parameter's option in your controller or application config.
- Digits
-
Checks if the value consists only of digits, this means it's just a regular expression checking for
^\d+$
. - Number
-
Utilises Scalar::Util's
looks_like_number
function to check if the value, well, looks like a number. - String[$re]
-
Takes a regular expression parameter and validates the string against it. E.g.
sub foo : Local Constraints( String[^\w+$] bar ) { }
CONSTRAINT OPTION REFERENCE
- takes
-
Specifies how many arguments are used as input.
- gives
-
Specifies how many values are going to arrive at the action.
- pre_filter
-
Callback, runs before
check
. Value is afterwards what was returned. - check
-
Validation check. Return true or false, or throw a validation exception with a
user_msg
through_()
. - post_filter
-
Like
pre_filter
, but after check.
METHODS
create_action
Overrides Catalyst::Controller's create_action
to wrap the original one in a Catalyst::Controller::Constraints::Action proxy object.
_fetch_constraint
Returns a constraint object by constraint name. If this type was already created, a cached version is returned.
_ACTION
Does the handling of the validation exceptions.
SEE ALSO
http://www.catalystframework.org/,
AUTHOR
Robert 'phaylon' Sedlacek - <phaylon@dunkelheit.at>
LICENSE AND COPYRIGHT
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
The full text of the license can be found in the LICENSE file included with this module.