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Common code used to be placed in AppModel, which led to a large and complicated pile of code. In general, common functionality is now implemented using traits.
AutoViewVars Trait
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History Trait
Models should record History at appropriate points to facilitate administrator review of actions affecting a Person record. HistoryTrait offers utility functions to simplify recording history. It is also possible to use HistoryRecordsTable directly, though it may be more complicated to do so.
PrimaryLink Trait
The Primary Link of a table is the foreign key to the most significant parent object, typically co_id or person_id. The Primary Link is used to automatically determine permissions, generate links, and other similar purposes.
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