Swift: How do I create a predicate with an Int value? - swift

Question

I am getting an EXC-BAD-ACCESS error on this statement:
var thisPredicate = NSPredicate(format: "(sectionNumber == %#"), thisSection)
thisSection has an Int value of 1 and displays the value 1 when I hover over it. But in the debug area I see this:
thisPredicate = (_ContiguousArrayStorage ...)
Another predicate using a String shows as ObjectiveC.NSObject
Why is this happening?

Answer 1

You will need to change %# for %i and remove the extra parenthesis:
Main problem here is that you are putting an Int where it's expecting an String.
Here's an example based on this post:
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 thisSection = 33
let thisPredicate = NSPredicate(format: "age == %i", thisSection)
let _people = (people as NSArray).filteredArrayUsingPredicate(thisPredicate)
_people
Another workaround would be to make thisSection's value an String, this can be achieved by String Interpolation or via description property of the Int.. lets say:
Changing:
let thisPredicate = NSPredicate(format: "age == %i", thisSection)
for
let thisPredicate = NSPredicate(format: "age == %#", thisSection.description)
or
let thisPredicate = NSPredicate(format: "age == %#", "\(thisSection)")
of course, you can always bypass this step and go for something more hardcoded (but also correct) as:
let thisPredicate = NSPredicate(format: "sectionNumber == \(thisSection)")
But take into account that for some weird reason
String Interpolation (this kind of structure: "\(thisSection)") where leading to retain cycles as stated here

Answer 2

When your data is safe or sanitized, you might try String Interpolation Swift Standard Library Reference. That would look something like this:
let thisSection = 1
let thisPredicate = NSPredicate(format: "sectionNumber == \(thisSection)")

Answer 3

On 64 bit architecture an Int maps to an Int64 and %i will overflow if its value is greater than 2,147,483,648.
You will need to change %# for %ld and remove the extra parenthesis.