composed_of in Rails - when to use it?

ruby-on-rails activerecord aggregate composite
user65663 picture user65663 · Apr 27, 2010 · Viewed 8.8k times · Source

When should you use ActiveRecord's composed_of class method?

Answer

Staelen picture Staelen · Apr 27, 2010

personally, i think this is useful when you have objects which are not stored in database, as shown in the database, e.g. temperature, gps location, balance, etc.

You might ask then why those are not stored in the database? In the database we only store a value, but if we want to attach useful, relevant methods to that value,

for e.g.

  1. in the case of temperature, we might need methods like to_fahrenheit, to_celsius, is_boiling_point?, etc

  2. in the case of gps location, we might need methods like distance_from(point), route_to(point), etc

so it's pretty useful when we can just create the classes for these objects, and use composed_of to initialize these objects on the fly

hope it helps =)

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