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NAME

Alzabo::Create::ForeignKey - Foreign key objects for schema creation.

SYNOPSIS

  use Alzabo::Create::ForeignKey;

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.

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).

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.

INHERITS FROM

Alzabo::ForeignKey

Note: all relevant documentation from the superclass has been merged into this document.

METHODS

new

The constructor takes the following parameters:

• columns_from => Alzabo::Create::Column object(s)
• columns_to => Alzabo::Create::Column object(s)

  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.

• cardinality => [1, 1], [1, 'n'], or ['n', 1]
• from_is_dependent => $boolean
• to_is_dependent => $boolean
• comment => $comment

  An optional comment.

It returns a new Alzabo::Create::ForeignKey object.

Throws: Alzabo::Exception::Params

table_from

table_to

Returns the relevant Alzabo::Create::Table object.

columns_from

columns_to

Returns the relevant Alzabo::Create::Column object(s) for the property as an array.

column_pairs

Returns an array of array references. The references are to two column array of Alzabo::Create::Column objects. These two columns correspond in the tables being linked together.

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.

Throws: Alzabo::Exception::Params

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.

Throws: Alzabo::Exception::Params

cardinality

Returns a two element array containing the two portions of the cardinality of the relationship. Each portion will be either '1' or 'n'.

from_is_dependent

to_is_dependent

Returns a boolean value indicating whether there is a dependency from one table to the other.

is_one_to_one

is_one_to_many

is_many_to_one

Returns a boolean value indicating what kind of relationship the object represents.

set_cardinality (\@cardinality) see above for details

Sets the cardinality of the foreign key.

Throws: Alzabo::Exception::Params

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).

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).

id

Returns a string uniquely identifying the foreign key.

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.

comment

Returns the comment associated with the foreign key object, if any.

set_comment ($comment)

Sets the comment for the foreign key object.

AUTHOR

Dave Rolsky, <autarch@urth.org>

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