Cocoa Programming for OS X: The Big Nerd Ranch Guide

For the More Curious: Filtering

As discussed earlier, NSArrayController arranges its objects by filtering and sorting. These two lenses correspond to properties on NSArrayController: filterPredicate, an NSPredicate, and sortDescriptors, an array of NSSortDescriptor objects.

NSPredicate is a logical operator that can be evaluated against an object. Predicates are typically instantiated using a format string. This predicate evaluates to true when raise is above 5%:

i​f​ ​l​e​t​ ​r​a​i​s​e​P​r​e​d​i​c​a​t​e​ ​=​ ​N​S​P​r​e​d​i​c​a​t​e​(​f​o​r​m​a​t​:​ ​"​r​a​i​s​e​ ​>​ ​0​.​0​5​"​)​ ​{​ ​ ​ ​ ​l​e​t​ ​m​a​t​c​h​e​d​:​ ​B​o​o​l​ ​=​ ​r​a​i​s​e​P​r​e​d​i​c​a​t​e​.​e​v​a​l​u​a​t​e​W​i​t​h​O​b​j​e​c​t​(​e​m​p​l​o​y​e​e​)​ ​ ​ ​ ​.​.​.​ ...