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.\" ========================================================================
.\"
.IX Title "Tangram::Type::Array::FromMany 3pm"
.TH Tangram::Type::Array::FromMany 3pm "2022-10-16" "perl v5.34.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Tangram::Type::Array::FromMany \- map Perl arrays using a link table
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&   use Tangram;
\&
\&   # or
\&   use Tangram::Core;
\&   use Tangram::Type::Array::FromMany;
\&
\&   $schema = Tangram::Schema\->new(
\&
\&      classes => { Company => { fields => {
\&
\&      array =>
\&      {
\&         # long form
\&         employee =>
\&         {
\&            class => \*(AqPerson\*(Aq,
\&            table => \*(AqCompany_employees\*(Aq,
\&            coll => \*(Aqcompany\*(Aq,
\&            item => \*(Aqemployee\*(Aq,
\&            slot => \*(Aqslot\*(Aq
\&         },
\&
\&         # short form
\&         assets => \*(AqAsset\*(Aq,
\&      }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Maps references to a Perl array. The persistent fields are grouped in
a hash under the \f(CW\*(C`array\*(C'\fR key in the field hash.
.PP
The array may contain only objects of persistent classes. These classes
must have a common persistent base class.
.PP
Tangram uses a link table to save the state of the collection. The
table has three columns, which contain
.IP "\(bu" 4
the id of the container objects
.IP "\(bu" 4
the id of the elements
.IP "\(bu" 4
the position of the element in the array
.PP
The field names are passed in a hash that associates a field name with
a field descriptor. The field descriptor may be either a hash or a
string. The hash uses the following fields:
.IP "\(bu" 4
class
.IP "\(bu" 4
aggreg
.IP "\(bu" 4
table
.IP "\(bu" 4
coll
.IP "\(bu" 4
item
.IP "\(bu" 4
slot
.IP "\(bu" 4
deep_update
.PP
Mandatory field \f(CW\*(C`class\*(C'\fR specifies the class of the elements.
.PP
Optional field \f(CW\*(C`aggreg\*(C'\fR specifies that the elements of the collection
must be removed (erased) from persistent storage along with the
containing object. The default is not to aggregate.
.PP
Optional field \f(CW\*(C`table\*(C'\fR sets the name of the link table. This
defaults to 'C_F', where C is the class of the containing object and F
is the field name.
.PP
Optional field \f(CW\*(C`coll\*(C'\fR sets the name the column containing the ids of
the containing objects. This defaults to 'coll'.
.PP
Optional field \f(CW\*(C`item\*(C'\fR sets the name the column containing the ids of
the elements. This defaults to 'item'.
.PP
Optional field \f(CW\*(C`slot\*(C'\fR sets the name the column containing the
position of the elements. This defaults to 'slot'.
.PP
Optional field \f(CW\*(C`deep_update\*(C'\fR specificies that all elements have to be
updated automatically when \f(CW\*(C`update\*(C'\fR is called on the collection
object. Automatic update ensures consisitency between the Perl
representation and the \s-1DBMS\s0 state, but degrades update performance so
use it with caution. The default is not to do automatic updates.
.PP
If the descriptor is a string, it is interpreted as the name of the
element's class. This is equivalent to specifying only the \f(CW\*(C`class\*(C'\fR
field in the hash variant.