~= operator in Swift

Simply use as a shortcut to “range”: you can construct a range and “~=” means “contains”.
(other can add more theoretical details, but the sense is this). Read it as “contains”

let n: Int = 100

// verify if n is in a range, say: 10 to 100 (included)

if n>=10 && n<=100 {
    print("inside!")
}

// using "patterns"
if 10...100 ~= n {
    print("inside! (using patterns)")

}

try with some values of n.

Is used widely for example in HTTP response:

if let response = response as? HTTPURLResponse , 200...299 ~= response.statusCode {
                let contentLength : Int64 = response.expectedContentLength
                completionHandler(contentLength)
            } else {
                completionHandler(nil)