DataMapper explained

DataMapper is an object-relational mapper library written in Ruby that follows the active record pattern even though the name implies it follows the data mapper pattern. While DataMapper 1 may not have achieved total decoupling between object and database suggested by the data mapper pattern, it appears DataMapper 2 intended to change this (a la Virtus, a library adapted from DataMapper).^[1] The DataMapper 2 project was renamed before launch and was released as Ruby Object Mapper (ROM) in August 2013.^[2]

Some features of DataMapper:^[3]

• Eager loading of child associations to avoid (N+1) queries
• Lazy loading of select properties, e.g., larger fields
• Query chaining, and not evaluating the query until absolutely necessary (using a lazy array implementation)
• An API not too heavily oriented to SQL databases

DataMapper was designed to be a more abstract ORM, not strictly SQL, based on Martin Fowler's enterprise pattern.^[4] As a result, DataMapper adapters have been built for other non-SQL databases, such as CouchDB,^[5] Apache Solr,^[6] and webservices such as Salesforce.com.^[7]

External links

• DataMapper homepage

Notes and References

1. Web site: datamapper wiki: Roadmap. GitHub.
2. Web site: Where is DataMapper 2?. Google Groups.
3. Web site: DataMapper - Why DataMapper? . 2010-10-12 . 2010-10-08 . https://web.archive.org/web/20101008025706/http://datamapper.org/why . dead .
4. Book: Fowler, Martin . David Rice . Matthew Foemmel . Edward Hieatt . Robert Mee . Randy Stafford . Patterns of Enterprise Application Architecture . Addison-Wesley . November 2002 . 0-321-12742-0.
5. Web site: Kabari's dm-couchdb-adapter at master - GitHub . . 2016-01-02 . https://web.archive.org/web/20090827004529/http://github.com/kabari/dm-couchdb-adapter/tree/master . 2009-08-27 . dead.
6. Web site: Lritter/Dm-solr-adapter. GitHub. 13 August 2019.
7. Web site: Dm-salesforce. GitHub. 22 February 2020.