MooseX::StrictConstructor - Make your object constructors blow up on unknown attributes


version 0.21


package My::Class;

use Moose;
use MooseX::StrictConstructor;

has 'size' => ( is => 'ro' );

# then later ...

# this blows up because color is not a known attribute
My::Class->new( size => 5, color => 'blue' );


Simply loading this module makes your constructors "strict". If your constructor is called with an attribute init argument that your class does not declare, then it calls Moose->throw_error(). This is a great way to catch small typos.

Subverting Strictness

You may find yourself wanting to have your constructor accept a parameter which does not correspond to an attribute.

In that case, you'll probably also be writing a BUILD() or BUILDARGS() method to deal with that parameter. In a BUILDARGS() method, you can simply make sure that this parameter is not included in the hash reference you return. Otherwise, in a BUILD() method, you can delete it from the hash reference of parameters.

sub BUILD {
    my $self   = shift;
    my $params = shift;

    if ( delete $params->{do_something} ) {


Please report any bugs or feature requests to, or through the web interface at I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

Bugs may be submitted at

I am also usually active on IRC as 'autarch' on irc://


The source code repository for MooseX-StrictConstructor can be found at


If you'd like to thank me for the work I've done on this module, please consider making a "donation" to me via PayPal. I spend a lot of free time creating free software, and would appreciate any support you'd care to offer.

Please note that I am not suggesting that you must do this in order for me to continue working on this particular software. I will continue to do so, inasmuch as I have in the past, for as long as it interests me.

Similarly, a donation made in this way will probably not make me work on this software much more, unless I get so many donations that I can consider working on free software full time (let's all have a chuckle at that together).

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Dave Rolsky <>



This software is Copyright (c) 2007 - 2017 by Dave Rolsky.

This is free software, licensed under:

The Artistic License 2.0 (GPL Compatible)

The full text of the license can be found in the LICENSE file included with this distribution.