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How to calculate division remainder using modulo

Swift version: 5.0

Paul Hudson    @twostraws   

Swift has a dedicated remainder operator in the form of %, and it’s used to return the remainder after dividing one number wholly into another. For example, 14 % 3 is 2, because you can fit four 3s into 14, and afterwards you have the remainder 2.

The remainder operator is helpful for calculating things like odd and even numbers – if you want alternate rows of your table to be a slightly different color, for example, you might write this:

for i in 1...10 {
    if i % 2 == 0 {
        print("Number is even")
    } else {
        print("Number is odd")
    }
}

You can also use the isMultiple(of:) method, which does more or less the same thing while being more readable:

for i in 1...10 {
    if i.isMultiple(of: 2) {
        print("Number is even")
    } else {
        print("Number is odd")
    }
}

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Available from iOS 8.0

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