CATO

A CATO is a "Computing and Transfer Object". It's purpose is to sort, filter and connect objects which belong together as well as transfer these objects. It is intended to be used as a link between Controller and Views like DTOs, but with some features.

CATOs and DTOs explained:

• A DTO MUST not have any method executing logic. It's solely purpose is to transfer data.
• A CATO MAY implement logic needed to do one or more of these tasks:
  • Sort the data
  • Filter the data
  • Transfer the data
  • Connect the data together
• A CATO MUST as well as DTO NOT alter the encapsulated data.

The CATO contains the logic or uses another object for the required task(s).

About CATO properties:

• A CATO MUST have at least one property referencing an object or multiple objects. These are called "storage properties". They MUST obey following rules:
  • Storage properties MUST have following annotation: @cato\storage
  • Storage properties MUST be publicly immutable once defined. (Set via or in constructor, no public setter)
  • Storage properties MAY contain the result of the computation.
  • Storage properties MUST contain only values of type object or object[].[1]
• Additional properties are OPTIONAL. They are called "buffer properties". They MUST obey ALL of the following rules:
  • Any buffer property MUST exclusively reference values from the storage properties.
  • They MUST have following annotation @cato\buffer
  • They MUST not be publicly writable (by visibility or setter)
• Buffer properties SHOULD be altered, set or unset by protected methods.

CATOs in general:

• A CATO MUST only be used where the logic does not apply to any of the given objects.
• A CATO MUST reside under the Domain/Model/CATO folder.
• The computation SHOULD be delayed to the latest possible point. [Lazyness]
• Results are expected to be static (they don't need to be computed again, because the result SHOULD NOT change). [Caching]
• The computing method SHOULD be called compute an SHOULD be at least protected.
• It SHOULD NOT be possible to force the CATO to recompute the result if it is static.
• A CATO MUST be silent (not void). It MUST NOT throw exceptions but it is RECOMMENDED to log errors.
• A CATO MUST always return the expected and annotated type.

This pattern was devised by Oliver Eglseder at 2015-12-17.