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.\" ========================================================================
.\"
.IX Title "Alzabo::Create::ForeignKey 3pm"
.TH Alzabo::Create::ForeignKey 3pm "2015-05-24" "perl v5.20.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH "NAME"
Alzabo::Create::ForeignKey \- Foreign key objects for schema creation.
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  use Alzabo::Create::ForeignKey;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
A foreign key is an object defined by several properties.  It
represents a relationship from a column or columns in one table to a
column or columns in another table.
.PP
This relationship is defined by its cardinality (one to one, one to
many, or many to one) and its dependencies (whether or not table X is
dependent on table Y, and vice versa).
.PP
Many to many relationships are not allowed.  However, you may indicate
such a relationship when using the
Alzabo::Create::Schema\->add_relation
method method, and it will create
the necessary intermediate linking table for you.
.SH "INHERITS FROM"
.IX Header "INHERITS FROM"
\&\f(CW\*(C`Alzabo::ForeignKey\*(C'\fR
.PP
Note: all relevant documentation from the superclass has been merged into this document.
.SH "METHODS"
.IX Header "METHODS"
.SS "new"
.IX Subsection "new"
The constructor takes the following parameters:
.IP "\(bu" 4
columns_from => \f(CW\*(C`Alzabo::Create::Column\*(C'\fR object(s)
.IP "\(bu" 4
columns_to => \f(CW\*(C`Alzabo::Create::Column\*(C'\fR object(s)
.Sp
These two parameters may be either a single column or a reference to
an array columns.  The number of columns in the two parameters must
match.
.IP "\(bu" 4
cardinality => [1, 1], [1, 'n'], or ['n', 1]
.IP "\(bu" 4
from_is_dependent => \f(CW$boolean\fR
.IP "\(bu" 4
to_is_dependent => \f(CW$boolean\fR
.IP "\(bu" 4
comment => \f(CW$comment\fR
.Sp
An optional comment.
.PP
It returns a new
\&\f(CW\*(C`Alzabo::Create::ForeignKey\*(C'\fR object.
.PP
Throws: \f(CW\*(C`Alzabo::Exception::Params\*(C'\fR
.SS "table_from"
.IX Subsection "table_from"
.SS "table_to"
.IX Subsection "table_to"
Returns the relevant \f(CW\*(C`Alzabo::Create::Table\*(C'\fR object.
.SS "columns_from"
.IX Subsection "columns_from"
.SS "columns_to"
.IX Subsection "columns_to"
Returns the relevant \f(CW\*(C`Alzabo::Create::Column\*(C'\fR object(s) for
the property as an array.
.SS "column_pairs"
.IX Subsection "column_pairs"
Returns an array of array references.  The references are to two
column array of \f(CW\*(C`Alzabo::Create::Column\*(C'\fR objects.  These
two columns correspond in the tables being linked together.
.ie n .SS "set_columns_from (""Alzabo::Create::Column"" object(s))"
.el .SS "set_columns_from (\f(CWAlzabo::Create::Column\fP object(s))"
.IX Subsection "set_columns_from (Alzabo::Create::Column object(s))"
Sets the column(s) that the relation is from.  This can be either a
single column object or a reference to an array of column objects.
.PP
Throws: \f(CW\*(C`Alzabo::Exception::Params\*(C'\fR
.ie n .SS "set_columns_to (""Alzabo::Create::Column"" object(s))"
.el .SS "set_columns_to (\f(CWAlzabo::Create::Column\fP object(s))"
.IX Subsection "set_columns_to (Alzabo::Create::Column object(s))"
Sets the column(s) that the relation is to.  This can be either a
single column object or a reference to an array of column objects.
.PP
Throws: \f(CW\*(C`Alzabo::Exception::Params\*(C'\fR
.SS "cardinality"
.IX Subsection "cardinality"
Returns a two element array containing the two portions of the
cardinality of the relationship.  Each portion will be either '1' or
\&'n'.
.SS "from_is_dependent"
.IX Subsection "from_is_dependent"
.SS "to_is_dependent"
.IX Subsection "to_is_dependent"
Returns a boolean value indicating whether there is a dependency from
one table to the other.
.SS "is_one_to_one"
.IX Subsection "is_one_to_one"
.SS "is_one_to_many"
.IX Subsection "is_one_to_many"
.SS "is_many_to_one"
.IX Subsection "is_many_to_one"
Returns a boolean value indicating what kind of relationship the
object represents.
.SS "set_cardinality (\e@cardinality) see above for details"
.IX Subsection "set_cardinality (@cardinality) see above for details"
Sets the cardinality of the foreign key.
.PP
Throws: \f(CW\*(C`Alzabo::Exception::Params\*(C'\fR
.SS "set_from_is_dependent ($boolean)"
.IX Subsection "set_from_is_dependent ($boolean)"
Indicates whether or not the first table in the foreign key is
dependent on the other (i.e. whether the 'from' table is dependent on
the 'to' table).
.SS "set_to_is_dependent ($boolean)"
.IX Subsection "set_to_is_dependent ($boolean)"
Indicates whether or not the second table in the foreign key is
dependent on the other (i.e. whether the 'to' table is dependent on
the 'from' table).
.SS "id"
.IX Subsection "id"
Returns a string uniquely identifying the foreign key.
.SS "is_same_relationship_as ($fk)"
.IX Subsection "is_same_relationship_as ($fk)"
Given a foreign key object, this returns true if the two objects
represent the same relationship.  However, the two objects may
represent the same relationship from different table's points of view.
.SS "comment"
.IX Subsection "comment"
Returns the comment associated with the foreign key object, if any.
.SS "set_comment ($comment)"
.IX Subsection "set_comment ($comment)"
Sets the comment for the foreign key object.
.SH "AUTHOR"
.IX Header "AUTHOR"
Dave Rolsky, <autarch@urth.org>