Swift 多类型和容器

数组存储不同类型数据

enum

enum IntOrString {
    case IntValue(Int)
    case StringValue(String)
}

let mixed = [IntOrString.IntValue(1),
             IntOrString.StringValue("two"),
             IntOrString.IntValue(3)]

for value in mixed {
    switch value {
    case let .IntValue(i):
        print(i * 2)
    case let .StringValue(s):
        print(s.capitalized)
    }
}

CustomStringConvertible

let mixed: [CustomStringConvertible] = [1, "two", 3]
for obj in mixed {
    print(obj.description)
}