SWIFT 3 Predicate for NSArray not working properly with numbers - nsarray

Question

I am learning to use predicates for filtering. I found a tutorial, but one aspect is not working 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 compile, but the last 2 produce no results even though I have a case where age = 33. Here is the test complete 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 would the last two work? You are passing a String in for an Int property. You need to pass in an Int to compare against 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.