DataMapper

[harell]

See [@Peaa, p. 165]

Main Features

• Store R6 objects in a relational database
• Retrieve R6 objects from a relational database

Under the Hood

• Store R6 objects in Entity–attribute–value model (EAV) data model
  • Entity is the object uid. If not supplied then use md5hash?
  • Attribute is one of four: public_field, public_method, private_field or private_method
  • Value is an unboxed json string (character)
• Optional: Include an additional entry that holds the result of serialize R6 object.

Hint

• http://richfitz.github.io/storr/articles/storr.html
• https://richfitz.github.io/thor/

Examples

Pseudocode: Mappin a person object to and from database

character <- person(given = "Bilbo", family = "Baggins")
class(character) # person

CharacterMapper$insert(character)
candidates <- CharacterMapper$find(given = "Bilbo")

class(candidates) # list of persons
identical(candidates[[1]], character)