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Declare::Constraints::Simple::Library::Operators(3pm) User Contributed Perl Documentation Declare::Constraints::Simple::Library::Operators(3pm)

NAME

Declare::Constraints::Simple::Library::Operators - Operators

SYNOPSIS

  # all hast to be valid
  my $and_constraint = And( IsInt,
                            Matches(qr/0$/) );
  # at least one has to be valid
  my $or_constraint = Or( IsInt, HasLength );
  # only one can be valid
  my $xor_constraint = XOr( IsClass, IsObject );
  # reverse validity
  my $not_an_integer = Not( IsInt );
  # case valid, validate 'bar' key depending on 'foo' keys value
  my $struct_prof = 
    And( IsHashRef,
         CaseValid( OnHashKeys(foo => IsEq("FooArray")),
                      OnHashKeys(bar => IsArrayRef),
                    OnHashKeys(foo => IsEq("FooHash")),
                      OnHashKeys(bar => IsHashRef) ));

DESCRIPTION

This module contains the frameworks operators. These constraint like elements act on the validity of passed constraints.

OPERATORS

And(@constraints)

Is true if all passed @constraints are true on the value. Returns the result of the first failing constraint.

Or(@constraints)

Is true if at least one of the passed @contraints is true. Returns the last failing constraint's result if false.

XOr(@constraints)

Valid only if a single one of the passed @constraints is valid. Returns the last failing constraint's result if false.

Not($constraint)

This is valid if the passed $constraint is false. The main purpose of this operator is to allow the easy reversion of a constraint's trueness.

CaseValid($test, $conseq, $test2, $conseq2, ...)

This runs every given $test argument on the value, until it finds one that returns true. If none is found, false is returned. On a true result, however, the corresponding $conseq constraint is applied to the value and it's result returned. This allows validation depending on other properties of the value:

  my $flexible = CaseValid( IsArrayRef,
                              And( HasArraySize(1,5), 
                                   OnArrayElements(0 => IsInt) ),
                            IsHashRef,
                              And( HasHashElements(qw( head tail )),
                                   OnHashKeys(head => IsInt) ));

Of course, you could model most of it probably with the other operators, but this is a bit more readable. For default cases use "ReturnTrue" from Declare::Constraints::Simple::Library::General as test.

SEE ALSO

Declare::Constraints::Simple, Declare::Constraints::Simple::Library

AUTHOR

Robert 'phaylon' Sedlacek "<phaylon@dunkelheit.at>"

LICENSE AND COPYRIGHT

This module is free software, you can redistribute it and/or modify it under the same terms as perl itself.

2021-01-09 perl v5.32.0