Dan Friedman > Class-DBI-DataMigration > Class::DBI::DataMigration::Mapper

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Name ^

Class::DBI::DataMigration::Mapper - Abstract class for mapping a single row in the source database to a single row in the target database.

Synopsis ^

 use Class::DBI::DataMigration::Mapper;

 # ... later ...
 # Assume we've retrieved a $source_object of class Class from the source
 # database, and have assembled $mappings, a ref to an appropriate hash of
 # Class::DBI::DataMigration::Mapping objects:

 my $mapper = new Class::DBI::DataMigration::Mapper({
     target_cdbi_class => Class, 
     mappings => $mappings,
     target_search_keys => \@search_keys
 });

 my $new_db_object = $mapper->map($source_object);

 # ... now $new_db_object is in the new database ... 

Description ^

Class::DBI::DataMigration::Mapper is an abstract parent class for objects that will map a single row at a time from the source database into a single row in the new one. This is accomplished via Class::DBI; it's assumed that appropriate classes exist representing the tables in the source and target databases.

Mapping is accomplished using a hash of instances of Class::DBI::DataMigration::Mapping objects.

Methods ^

mappings

Gets/sets a ref to a hash of Class::DBI::DataMigration::Mapping objects, keyed on keys into the source class whose values will be used to produce values for the target class.

target_cdbi_class

Gets/sets the target class in which to build a new object (or edit an existing one) using the mappings and the source_object supplied to map()

target_keys

Gets/sets a ref to a hash that acts as a dictionary between the target and source classes; the keys in this hash are keys into the target class, and the values are the corresponding keys into the source class.

target_search_keys

Gets/sets a ref to a list of keys that will be used during mapping to search for a target class object; if found, data from the matching source db object will be used to edit the already-existing target db object. Otherwise, a new object will be created in the target db. If target_search_keys is left empty, no searching will be done, and all objects from the source db will be mirrored as new objects in the target db.

map

Expects one parameter: the source_object in the source database whose data is to be mapped into an object in the target_cdbi_class.

This method causes the Mapper to iterate through its target_keys hash, calling map() on each mapping with the source object and the source key under which it was stored in the mappings hash. The returned values of each of these map() calls are collected into a hash and used to do one of the following:

- if an object matching our target_search_keys in the data hash is found in the target_cdbi_class (we use the first one found), that object is synchronized using the rest of the data in the data hash and returned; and,

- if our target_search_keys is empty, or if no object matching the those keys in the data hash exists in the target_cdbi_class, a new target class object is created and returned.

If errors are encountered during this process, an error message is returned instead of the affected object.

Subclasses may do something fancier.

See Also ^

Class::DBI::DataMigration

Author ^

Dan Friedman <lamech@cpan.org>

Copyright & License ^

Copyright 2004 Dan Friedman, All Rights Reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

Please note that these modules are not products of or supported by the employers of the various contributors to the code.

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