SWIFT 3 Predicate for NSArray not working properly with numbers

Question

I study the use of predicates for filtering. I found a tutorial, but one aspect does not work for me in Swift 3. Here is some specific code:

let ageIs33Predicate01 = NSPredicate(format: "age = 33") //THIS WORKS let ageIs33Predicate02 = NSPredicate(format: "%K = 33", "age") //THIS WORKS let ageIs33Predicate03 = NSPredicate(format: "%K = %@", "age","33") //THIS DOESN'T WORK let ageIs33Predicate04 = NSPredicate(format: "age = %@","33") //THIS DOESN'T WORK 

All 4 compilation, but the last 2 do not give results, even if I have a case where age = 33. Here is the test test code from the tutorial:

 import Foundation class Person: NSObject { let firstName: String let lastName: String let age: Int init(firstName: String, lastName: String, age: Int) { self.firstName = firstName self.lastName = lastName self.age = age } override var description: String { return "\(firstName) \(lastName)" } } let alice = Person(firstName: "Alice", lastName: "Smith", age: 24) let bob = Person(firstName: "Bob", lastName: "Jones", age: 27) let charlie = Person(firstName: "Charlie", lastName: "Smith", age: 33) let quentin = Person(firstName: "Quentin", lastName: "Alberts", age: 31) let people = [alice, bob, charlie, quentin] let ageIs33Predicate01 = NSPredicate(format: "age = 33") let ageIs33Predicate02 = NSPredicate(format: "%K = 33", "age") let ageIs33Predicate03 = NSPredicate(format: "%K = %@", "age","33") let ageIs33Predicate04 = NSPredicate(format: "age = %@","33") (people as NSArray).filtered(using: ageIs33Predicate01) // ["Charlie Smith"] (people as NSArray).filtered(using: ageIs33Predicate02) // ["Charlie Smith"] (people as NSArray).filtered(using: ageIs33Predicate03) // [] (people as NSArray).filtered(using: ageIs33Predicate04) // [] 

What am I doing wrong? Thanks.

Answer 1

Why do we need the last two? You pass String in for the Int property. You need to pass Int to compare with the Int property.

Change the last two to:

 let ageIs33Predicate03 = NSPredicate(format: "%K = %d", "age", 33) let ageIs33Predicate04 = NSPredicate(format: "age = %d", 33) 

Note the change in the format specifier from %@ to %d .