Swift: Test class type in switch statement

Question

In Swift you can check the class type of an object using \'is\'. How can I incorporate this into a \'switch\' block?

I think it\'s not possible, so I\'m wondering w

Answer 1

In case you don't have a value, just any object:

swift 4

func test(_ val:Any) {
    switch val {
    case is NSString:
        print("it is NSString")
    case is String:
        print("it is a String")
    case is Int:
        print("it is int")
    default:
        print(val)
    }
}


let str: NSString = "some nsstring value"
let i:Int=1
test(str) 
// it is NSString
test(i) 
// it is int

Answer 2

Putting up the example for "case is - case is Int, is String:" operation, where multiple cases can be used clubbed together to perform the same activity for Similar Object types. Here "," separating the types in case is operating like a OR operator.

switch value{
case is Int, is String:
    if value is Int{
        print("Integer::\(value)")
    }else{
        print("String::\(value)")
    }
default:
    print("\(value)")
}

Demo Link

Answer 3

You absolutely can use is in a switch block. See "Type Casting for Any and AnyObject" in the Swift Programming Language (though it's not limited to Any of course). They have an extensive example:

for thing in things {
    switch thing {
    case 0 as Int:
        println("zero as an Int")
    case 0 as Double:
        println("zero as a Double")
    case let someInt as Int:
        println("an integer value of \(someInt)")
    case let someDouble as Double where someDouble > 0:
        println("a positive double value of \(someDouble)")
// here it comes:
    case is Double:
        println("some other double value that I don't want to print")
    case let someString as String:
        println("a string value of \"\(someString)\"")
    case let (x, y) as (Double, Double):
        println("an (x, y) point at \(x), \(y)")
    case let movie as Movie:
        println("a movie called '\(movie.name)', dir. \(movie.director)")
    default:
        println("something else")
    }
}

Answer 4

I like this syntax:

switch thing {
case _ as Int: print("thing is Int")
case _ as Double: print("thing is Double")
}

since it gives you the possibility to extend the functionality fast, like this:

switch thing {
case let myInt as Int: print("\(myInt) is Int")
case _ as Double: print("thing is Double")
}