In some cases, you already have a recordset, but only you need to operate on certain records. You can, of course, iterate on the recordset, checking for the condition on each iteration and acting depending on the result of the check. It can be easier, and in some cases, more efficient, to construct a new recordset containing only the interesting records and calling a single operation on that recordset.
This recipe shows you how to use the
filter() method to extract a subset of recordsets based on a condition.
We will reuse the simplified
library.book model that was shown in the Creating new records recipe. This recipe defines a method to extract books that have multiple authors from a supplied recordset.
How to do it...
To extract records that have multiple authors from a recordset, you need to perform the following steps:
- Define the method to accept the original recordset: