--- /dev/null
+.\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.3
+.\"
+.\" Standard preamble:
+.\" ========================================================================
+.de Sh \" Subsection heading
+.br
+.if t .Sp
+.ne 5
+.PP
+\fB\\$1\fR
+.PP
+..
+.de Sp \" Vertical space (when we can't use .PP)
+.if t .sp .5v
+.if n .sp
+..
+.de Vb \" Begin verbatim text
+.ft CW
+.nf
+.ne \\$1
+..
+.de Ve \" End verbatim text
+.ft R
+.fi
+..
+.\" Set up some character translations and predefined strings. \*(-- will
+.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
+.\" double quote, and \*(R" will give a right double quote. | will give a
+.\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used to
+.\" do unbreakable dashes and therefore won't be available. \*(C` and \*(C'
+.\" expand to `' in nroff, nothing in troff, for use with C<>.
+.tr \(*W-|\(bv\*(Tr
+.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
+.ie n \{\
+. ds -- \(*W-
+. ds PI pi
+. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
+. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
+. ds L" ""
+. ds R" ""
+. ds C` ""
+. ds C' ""
+'br\}
+.el\{\
+. ds -- \|\(em\|
+. ds PI \(*p
+. ds L" ``
+. ds R" ''
+'br\}
+.\"
+.\" If the F register is turned on, we'll generate index entries on stderr for
+.\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
+.\" entries marked with X<> in POD. Of course, you'll have to process the
+.\" output yourself in some meaningful fashion.
+.if \nF \{\
+. de IX
+. tm Index:\\$1\t\\n%\t"\\$2"
+..
+. nr % 0
+. rr F
+.\}
+.\"
+.\" For nroff, turn off justification. Always turn off hyphenation; it makes
+.\" way too many mistakes in technical documents.
+.hy 0
+.if n .na
+.\"
+.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
+.\" Fear. Run. Save yourself. No user-serviceable parts.
+. \" fudge factors for nroff and troff
+.if n \{\
+. ds #H 0
+. ds #V .8m
+. ds #F .3m
+. ds #[ \f1
+. ds #] \fP
+.\}
+.if t \{\
+. ds #H ((1u-(\\\\n(.fu%2u))*.13m)
+. ds #V .6m
+. ds #F 0
+. ds #[ \&
+. ds #] \&
+.\}
+. \" simple accents for nroff and troff
+.if n \{\
+. ds ' \&
+. ds ` \&
+. ds ^ \&
+. ds , \&
+. ds ~ ~
+. ds /
+.\}
+.if t \{\
+. ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
+. ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
+. ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
+. ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
+. ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
+. ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
+.\}
+. \" troff and (daisy-wheel) nroff accents
+.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
+.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
+.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
+.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
+.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
+.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
+.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
+.ds ae a\h'-(\w'a'u*4/10)'e
+.ds Ae A\h'-(\w'A'u*4/10)'E
+. \" corrections for vroff
+.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
+.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
+. \" for low resolution devices (crt and lpr)
+.if \n(.H>23 .if \n(.V>19 \
+\{\
+. ds : e
+. ds 8 ss
+. ds o a
+. ds d- d\h'-1'\(ga
+. ds D- D\h'-1'\(hy
+. ds th \o'bp'
+. ds Th \o'LP'
+. ds ae ae
+. ds Ae AE
+.\}
+.rm #[ #] #H #V #F C
+.\" ========================================================================
+.\"
+.IX Title "Moose::Cookbook::Basics::Recipe10 3"
+.TH Moose::Cookbook::Basics::Recipe10 3 "2009-08-11" "perl v5.8.7" "User Contributed Perl Documentation"
+.SH "NAME"
+Moose::Cookbook::Basics::Recipe10 \- Using BUILDARGS and BUILD to hook into object construction
+.SH "SYNOPSIS"
+.IX Header "SYNOPSIS"
+.Vb 1
+\& package Person;
+.Ve
+.PP
+.Vb 5
+\& has 'ssn' => (
+\& is => 'ro',
+\& isa => 'Str',
+\& predicate => 'has_ssn',
+\& );
+.Ve
+.PP
+.Vb 5
+\& has 'country_of_residence' => (
+\& is => 'ro',
+\& isa => 'Str',
+\& default => 'usa'
+\& );
+.Ve
+.PP
+.Vb 4
+\& has 'first_name' => (
+\& is => 'ro',
+\& isa => 'Str',
+\& );
+.Ve
+.PP
+.Vb 4
+\& has 'last_name' => (
+\& is => 'ro',
+\& isa => 'Str',
+\& );
+.Ve
+.PP
+.Vb 3
+\& around BUILDARGS => sub {
+\& my $orig = shift;
+\& my $class = shift;
+.Ve
+.PP
+.Vb 7
+\& if ( @_ == 1 && ! ref $_[0] ) {
+\& return $class\->$orig(ssn => $_[0]);
+\& }
+\& else {
+\& return $class\->$orig(@_);
+\& }
+\& };
+.Ve
+.PP
+.Vb 2
+\& sub BUILD {
+\& my $self = shift;
+.Ve
+.PP
+.Vb 5
+\& if ( $self\->country_of_residence eq 'usa' ) {
+\& die 'Cannot create a Person who lives in the USA without an ssn.'
+\& unless $self\->has_ssn;
+\& }
+\& }
+.Ve
+.SH "DESCRIPTION"
+.IX Header "DESCRIPTION"
+This recipe demonstrates the use of \f(CW\*(C`BUILDARGS\*(C'\fR and \f(CW\*(C`BUILD\*(C'\fR. By
+defining these methods, we can hook into the object construction
+process without overriding \f(CW\*(C`new\*(C'\fR.
+.PP
+The \f(CW\*(C`BUILDARGS\*(C'\fR method is called \fIbefore\fR an object has been
+created. It is called as a class method, and receives all of the
+parameters passed to the \f(CW\*(C`new\*(C'\fR method. It is expected to do something
+with these arguments and return a hash reference. The keys of the hash
+must be attribute \f(CW\*(C`init_arg\*(C'\fRs.
+.PP
+The primary purpose of \f(CW\*(C`BUILDARGS\*(C'\fR is to allow a class to accept
+something other than named arguments. In the case of our \f(CW\*(C`Person\*(C'\fR
+class, we are allowing it to be called with a single argument, a
+social security number:
+.PP
+.Vb 1
+\& my $person = Person\->new('123\-45\-6789');
+.Ve
+.PP
+The key part of our \f(CW\*(C`BUILDARGS\*(C'\fR is this conditional:
+.PP
+.Vb 3
+\& if ( @_ == 1 && ! ref $_[0] ) {
+\& return $class\->$orig(ssn => $_[0]);
+\& }
+.Ve
+.PP
+By default, Moose constructors accept a list of key-value pairs, or a
+hash reference. We need to make sure that \f(CW$_[0]\fR is not a reference
+before assuming it is a social security number.
+.PP
+We call the original \f(CW\*(C`BUILDARGS\*(C'\fR method to handle all the other
+cases. You should always do this in your own \f(CW\*(C`BUILDARGS\*(C'\fR methods,
+since Moose::Object provides its own \f(CW\*(C`BUILDARGS\*(C'\fR method that
+handles hash references and a list of key-value pairs.
+.PP
+The \f(CW\*(C`BUILD\*(C'\fR method is called \fIafter\fR the object is constructed, but
+before it is returned to the caller. The \f(CW\*(C`BUILD\*(C'\fR method provides an
+opportunity to check the object state as a whole. This is a good place
+to put logic that cannot be expressed as a type constraint on a single
+attribute.
+.PP
+In the \f(CW\*(C`Person\*(C'\fR class, we need to check the relationship between two
+attributes, \f(CW\*(C`ssn\*(C'\fR and \f(CW\*(C`country_of_residence\*(C'\fR. We throw an exception
+if the object is not logically consistent.
+.SH "MORE CONSIDERATIONS"
+.IX Header "MORE CONSIDERATIONS"
+This recipe is made significantly simpler because all of the
+attributes are read\-only. If the \f(CW\*(C`country_of_residence\*(C'\fR attribute
+were settable, we would need to check that a Person had an \f(CW\*(C`ssn\*(C'\fR if
+the new country was \f(CW\*(C`usa\*(C'\fR. This could be done with a \f(CW\*(C`before\*(C'\fR
+modifier.
+.SH "CONCLUSION"
+.IX Header "CONCLUSION"
+We have repeatedly discouraged overriding \f(CW\*(C`new\*(C'\fR in Moose
+classes. This recipe shows how you can use \f(CW\*(C`BUILDARGS\*(C'\fR and \f(CW\*(C`BUILD\*(C'\fR
+to hook into object construction without overriding \f(CW\*(C`new\*(C'\fR
+.PP
+The \f(CW\*(C`BUILDARGS\*(C'\fR method lets us expand on Moose's built-in parameter
+handling for constructors. The \f(CW\*(C`BUILD\*(C'\fR method lets us implement
+logical constraints across the whole object after it is created.
+.SH "AUTHOR"
+.IX Header "AUTHOR"
+Dave Rolsky <autarch@urth.org>
+.SH "COPYRIGHT AND LICENSE"
+.IX Header "COPYRIGHT AND LICENSE"
+Copyright 2006\-2009 by Infinity Interactive, Inc.
+.PP
+<http://www.iinteractive.com>
+.PP
+This library is free software; you can redistribute it and/or modify
+it under the same terms as Perl itself.
projects / catagits/Gitalist.git / blobdiff