NSPredicate

• NSPredicate is Cocoa's means of describing queries, like you might use with a database.

• You can use NSPredicate with database style API like Core Data and Spotlight. (These two technologies are not covered in book but whatever is covered in this chapter can be applied with them also)

• Like pointers, classes, KVC even NSPredicate is another means of indirection.

• NSPredicate does checking rather than asking explicitly in the code.