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.\"
.IX Title "Declare::Constraints::Simple::Library::Hash 3pm"
.TH Declare::Constraints::Simple::Library::Hash 3pm "2018-03-31" "perl v5.26.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
Declare::Constraints::Simple::Library::Hash \- Hash Constraints
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  my $constraint = And(
\&
\&    # make sure all keys are present
\&    HasAllKeys( qw(foo bar) ),
\&
\&    # constraints for the keys
\&    OnHashKeys( foo => IsInt, bar => HasLength )
\&
\&  );
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module contains all constraints that can be applied to hash
references.
.SS "HasAllKeys(@keys)"
.IX Subsection "HasAllKeys(@keys)"
The value has to be a hashref, and contain all keys listed in 
\&\f(CW@keys\fR to pass this constraint.
.PP
The stack or path part of \f(CW\*(C`HasAllKeys\*(C'\fR is \f(CW\*(C`HasAllKeys[$key]\*(C'\fR where
\&\f(CW$key\fR is the missing key.
.ie n .SS "OnHashKeys(key => $constraint, key => $constraint, ...)"
.el .SS "OnHashKeys(key => \f(CW$constraint\fP, key => \f(CW$constraint\fP, ...)"
.IX Subsection "OnHashKeys(key => $constraint, key => $constraint, ...)"
This allows you to pass a constraint for each specific key in
a hash reference. If a specified key is not in the validated
hash reference, the validation for this key is not done. To make
a key a requirement, use HasAllKeys(@keys) above in combination
with this, e.g. like:
.PP
.Vb 4
\&  And( HasAllKeys( qw(foo bar baz) )
\&       OnHashKeys( foo => IsInt,
\&                   bar => Matches(qr/bar/),
\&                   baz => IsArrayRef( HasLength )));
.Ve
.PP
Also, as you might see, you don't have to check for \f(CW\*(C`IsHashRef\*(C'\fR
validity here. The hash constraints are already doing that by
themselves.
.PP
The stack or path part of \f(CW\*(C`OnHashKeys\*(C'\fR looks like \f(CW\*(C`OnHashKeys[$key]\*(C'\fR
where \f(CW$key\fR is the key of the failing value.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Declare::Constraints::Simple, Declare::Constraints::Simple::Library
.SH "AUTHOR"
.IX Header "AUTHOR"
Robert 'phaylon' Sedlacek \f(CW\*(C`<phaylon@dunkelheit.at>\*(C'\fR
.SH "LICENSE AND COPYRIGHT"
.IX Header "LICENSE AND COPYRIGHT"
This module is free software, you can redistribute it and/or modify it 
under the same terms as perl itself.