Hook: Define DataBasket Entry Grouping

Requirement

The entries of a DataBasket need to be grouped before displaying them.

For example, if a user removes 7 apples and later 5 more apples from a CountingStock, using the same DataBasket for both operations, the DataBasket might afterwards contain two entries, one describing the removal of 7 apples, the other one the removal of the 5 additional apples. When presenting the contents of the DataBasket, you might want to hide these details from the user and rather present one entry telling about 12 apples having been removed from the CountingStock. In this case you may have to group the DataBasket's entries before displaying them. This is an implementation of the hook.

Method of Adaptation

Enable Feature

Level of Support

Parameter Pattern

HotSpot

Standard User Interaction for Data Management

Participants

DataBasketEntryGrouper, NewEntryGrouper

Changes

1. implementation NewEntryGrouper of DataBasketEntryGrouper.
2. NewEntryGrouper.canGroup implements DataBasketEntryGrouper.canGroup .
3. NewEntryGrouper.group implements DataBasketEntryGrouper.group .

Constraints

• The relation imposed by canGroup must be an equality relation, i.e. it must be
  • reflexive for all entries a canGroup (a, a) must return true .
  • symmetric for all entries a and b canGroup (a, b) == canGroup (b, a).
  • transitive for all entries a, b and c if canGroup (a, b) returns true and canGroup (b, c) returns true then canGroup (a, c) must also return true .
• canGroup must never throw a ClassCastException .
• group will be given tuples of entries for which canGroup returned true . It must create a new entry that represents the grouping of the two entries.

  If a and b are the two entries to be grouped and c is the grouped entry, canGroup (a, c) as well as canGroup (b, c) must return true .

Comments

• An instance of the new class is passed as a parameter when creating a new data.swing.DataBasketTableModel , data.swing.JDataBasketTable or to one of the create methods in data.stdforms.SingleTableFormSheet or data.stdforms.TwoTableFormSheet .