Calling new()

new() is called as "my($obj) = DBIx::Tree -> new(k1 => v1, k2 => v2, ...)".

It returns a new object of type "DBIx::Tree".

Key-value pairs accepted in the parameter list:

o columns => $ara_ref

A reference to a list of three column names that can be found in the table/result set:

  id_col:     The name of the column containing the unique id.
  label_col:  The name of the column containing the textual data
              of the row, like a name.
  parent_col: The name of the column containing the id of the
              row's parent.
    

Optional additional columns; note that these will only be used in queries built by DBIx::Tree from 'table' specifications - i.e. they will not be used with 'sth'- or 'sql'-type query parameters (presumably you can provide this functionality yourself when using one of those query types).

  order_col:  The name of a column to use for ordering the results;
              defaults to the column name specified by label_col.
              This column name does not need to exist in the result
              set, but should exist in the table being queried.
  order_dir:  An SQL directive specifying the directionality of the
              ordering; for most databases this is either 'ASC' or
              'DESC'.  The default is an empty string, which leaves
              the decision to the database (in most cases, this will
              be ascending)
    

o connection => $dbh

A DBI connection handle. This parameter is always required. Earlier versions of this doc said it was not necessary when using the $sth option, but in that case omitting it gets an error on prepare_cached.

o limit => $integer

Limit the number of rows using an SQL LIMIT clause - not all SQL servers support this. This feature was supplied by Ilia Lobsanov <ilia@lobsanov.com>

o match_data => $string

The value of a partial match to look for - if this is supplied, only rows whose label_col matches (match_data + '%') this will be selected. This feature was supplied by Ilia Lobsanov <ilia@lobsanov.com>

o method => $sub_name

A callback method to be invoked each time a tree item is encountered. This method will be given a hash as a parameter, containing the following elements:

  item:        the name of the item
  level (1-n): the nesting level of the item.
  id:          the unique id of the item.
  parent_id:   an array ref containing the geneology of parent id's
               for the current item
  parent_name: an array ref containing the geneology of parent name's
               for the current item
    

If the 'threshold' parameter has been set (either via the new() constructor or in the call to traverse()), the callback will only occur if the tree item is 'threshold' or more levels deep in the hierarchy.

o post_method => $sub_name

A callback method to be invoked after all the children of a tree item have been encountered. This method will be given a hash as a parameter, containing the following elements:

  item:        the name of the item
  level (0-n): the nesting level of the item.
  id:          the unique id of the item.
  parent_id:   an array ref containing the geneology of parent id's
               for the current item
  parent_name: an array ref containing the geneology of parent name's
               for the current item
    

If the 'threshold' parameter has been set (either via the new() constructor or in the call to traverse()), the callback will only occur if the tree item is 'threshold' or more levels deep in the hierarchy.

o recursive => $Boolean

Specifies which of two methods DBIx::Tree will use to traverse the tree. The default is non-recursively, which is efficient in that it requires only a single database query, but it also loads the entire tree into memory at once. The recursive method queries the database repetitively, but has smaller memory requirements. The recursive method will also be more efficient when an alternative start_id is specified. Note that if you supply both a limit argument and a threshold argument (implying that you want to see at most N records at or below the given threshold), the recursive method will be used automatically for efficiency.

o sql => $sql_statement

A string containing a custom "SELECT" SQL query statement that returns the hierarchical data. Unnecessary if all of the id/label/parent columns come from the same table specified by the 'table' parameter. Use only when you need to bring in supplementary information from other tables via custom "joins". Note that providing an 'sql' argument will override any other 'table' specification.

o start_id => $integer

The unique id of the root item. Defaults to 1. May be overriden by the 'start_id' argument to traverse().

o sth => $db_sth

A prepared (but not yet executed!) DBI statement handle. Unnecessary if you plan to provide either a basic table name via 'table' or a custom SQL statement via 'sql'. Note that providing an 'sth' argument will override any other 'sql' or 'table' specification.

o table => $table_name

The database table containing the hierarchical data. Unnecessary if you plan to provide either a custom SQL statement via the 'sql' parameter or a prepared DBI statement handle via the 'sth' parameter.

o threshold => $integer

The level in the hierarchical tree at which to begin processing items. The root of the tree is considered to be at level 1. May be overriden by the 'threshold' argument to traverse().

new(%args)

  my $tree = new DBIx::Tree(connection => $dbh,
                            table      => $table,
                            sql        => $sql,
                            sth        => $sth,
                            method     => sub { disp_tree(@_) },
                            columns    => [$id_col, $label_col, $parent_col],
                            start_id   => $start_id,
                            threshold  => $threshold,
                            match_data => $match_data,
                            limit      => $limit
                            recursive  => 1 || 0);

traverse(%args)

Begins a depth-first traversal of the hierarchical tree. The optional %args hash provides locally overriding values for the identical parameters set in the new() constructor.