Swift:测试switch语句中的类类型

你完全可以在switch块中使用is。参见Swift编程语言中的“Any和AnyObject的类型强制转换”(当然不限于Any)。他们有一个广泛的例子:

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")
}
}

举一个“case is - case是Int，是String:”操作的例子，其中多个case可以组合在一起，为类似对象类型执行相同的活动。这里，分隔case类型的”、“操作符类似于或操作符。

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

Demo Link . Demo Link

如果你没有值，任何对象都可以:

斯威夫特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

我喜欢这样的语法:

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

因为它让你有可能快速扩展功能，就像这样:

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