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.\" ========================================================================
.\"
.IX Title "MooseX::SetOnce 3pm"
.TH MooseX::SetOnce 3pm "2022-06-15" "perl v5.34.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
MooseX::SetOnce \- write\-once, read\-many attributes for Moose
.SH "VERSION"
.IX Header "VERSION"
version 0.200002
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
Add the \*(L"SetOnce\*(R" trait to attributes:
.PP
.Vb 3
\&  package Class;
\&  use Moose;
\&  use MooseX::SetOnce;
\&
\&  has some_attr => (
\&    is     => \*(Aqrw\*(Aq,
\&    traits => [ qw(SetOnce) ],
\&  );
.Ve
.PP
\&...and then you can only set them once:
.PP
.Vb 1
\&  my $object = Class\->new;
\&
\&  $object\->some_attr(10);  # works fine
\&  $object\->some_attr(20);  # throws an exception: it\*(Aqs already set!
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The 'SetOnce' attribute lets your class have attributes that are not lazy and
not set, but that cannot be altered once set.
.PP
The logic is very simple:  if you try to alter the value of an attribute with
the SetOnce trait, either by accessor or writer, and the attribute has a value,
it will throw an exception.
.PP
If the attribute has a clearer, you may clear the attribute and set it again.
.SH "AUTHOR"
.IX Header "AUTHOR"
Ricardo \s-1SIGNES\s0 <rjbs@cpan.org>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
This software is copyright (c) 2013 by Ricardo \s-1SIGNES.\s0
.PP
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.