How to know if a number is odd or even in Swift?

I have an array of numbers typed Int.

I want to loop through this array and determine if each number is odd or even.

How can I determine if a number is odd or even in Swift?

var myArray = [23, 54, 51, 98, 54, 23, 32];
for myInt: Int in myArray{
  if myInt % 2 == 0 {
    println("\(myInt) is even number")
  } else {
    println("\(myInt) is odd number")
  }
}

Use the % Remainder Operator (aka the Modulo Operator) to check if a number is even:

if yourNumber % 2 == 0 {
  // Even Number
} else {
  // Odd Number
}

or, use remainder(dividingBy:) to make the same check:

if yourNumber.remainder(dividingBy: 2) == 0 {                
  // Even Number 
} else {
  // Odd Number
}

Swift 5 adds the function isMultiple(of:) to the BinaryInteger protocol.

let even = binaryInteger.isMultiple(of: 2) 
let odd = !binaryInteger.isMultiple(of: 2)

This function can be used in place of % for odd/even checks.

---

This function was added via the Swift Evolution process:

• Preliminary Discussion in Swift Forum
• Swift Evolution Proposal
• Accepted Swift Evolution Implementation

Notably, isEven and isOdd were proposed but not accepted in the same review:

> Given the addition of isMultiple(of:), the Core Team feels that isEven and isOdd offer no substantial advantages over isMultiple(of: 2). > > Therefore, the proposal is accepted with modifications. isMultiple(of:) is accepted but isEven and isOdd are rejected.

If desired, those methods can be added easily through extension:

extension BinaryInteger {
    var isEven: Bool { isMultiple(of: 2) }
    var isOdd:  Bool { !isEven }
}

"Parity" is the name for the mathematical concept of Odd and Even:

> https://en.wikipedia.org/wiki/Parity_(mathematics)

You can extend the Swift BinaryInteger protocol to include a parity enumeration value:

enum Parity {
    case even, odd
    
    init<T>(_ integer: T) where T : BinaryInteger {
        self = integer.isMultiple(of: 2) ? .even : .odd
    }
}

extension BinaryInteger {
    var parity: Parity { Parity(self) }
}

which enables you to switch on an integer and elegantly handle the two cases:

switch 42.parity {
case .even:
    print("Even Number")
case .odd:
    print("Odd Number")
}

You can use filter method:

let numbers = [1,2,3,4,5,6,7,8,9,10]
let odd = numbers.filter { $0 % 2 == 1 }
let even = numbers.filter { $0 % 2 == 0 }