Swift: Test class type in switch statement

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日久生厌
日久生厌 2020-12-02 04:41

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

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  •  误落风尘
    2020-12-02 05:11

    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")
        }
    }
    

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